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The Arctic Ocean (AO) undergoes profound changes of its physical and biotic environments due to climate change. The greater light exposure and stratification alter its plankton ecosystem structure, functioning and productivity promoting oligotrophy in some areas as the Beaufort Sea. A one-dimension (1-D) physical-biological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used (i) to infer the functioning and nitrogen fluxes within the summer plankton ecosystem and (ii) to assess the model sensitivity to key light-associated processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen (i.e. photoammonification process) was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. It contributed to ca. two-thirds and one-third of the simulated surface (0-10 m) and depth-integrated primary and bacterial production, respectively. The model also suggested that carbon to chlorophyll ratios for small (<5 µm) phytoplankton (ca. 15-45 gg-1) lower than those commonly used in biogeochemical models applied to the AO were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional groups competition, nutrient recycling and primary production in poorly productive waters of the AO as they are expected to expand rapidly. [ABSTRACT FROM AUTHOR]

This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. Distribution patterns of phytoplankton groups in the late summers of 2008-2010 were analyzed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years -- the sea ice retreat in 2008 was 1-2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure. [ABSTRACT FROM AUTHOR]

The vertical distribution of radiolarians was investigated using a vertical multiple plankton sampler (100-0, 250-100, 500-250 and 1000-500 m water depths, 62 µmmesh size) at the Northwind Abyssal Plain and southwestern Canada Basin in September 2013. To investigate seasonal variations in the flux of radiolarians in relation to sea-ice and water masses, time series sediment trap system was moored at Station NAP (75°00' N, 162°00' W, bottom depth 1975 m) in the western Arctic Ocean during October 2010-September 2012. We showed characteristics of fourteen abundant radiolarian taxa related to the vertical hydrographic structure in the western Arctic Ocean. We found the Ceratocyrtis histricosus, a warm Atlantic water species, in net samples, indicating that it has extended its habitat into the Pacific Winter Water. The radiolarian flux was comparable to that in the North Pacific Oceans. Amphimelissa setosa was dominant during the open water and the beginning and the end of ice cover seasons with well-grown ice algae, ice fauna and with alternation of stable water masses and deep vertical mixing. During the sea-ice cover season, however, oligotrophic and cold-water tolerant Actinommidae was dominant and the productivity of radiolaria was lower and its species diversity was greater, which might be associated with the seasonal increase of solar radiation that induce the growth of algae on the ice and the other phytoplankton species under the sea-ice. These indicated that the dynamics of sea-ice was a major factor affecting the productivity, distribution, and composition of radiolarian fauna. [ABSTRACT FROM AUTHOR]

Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining the temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air/sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification using KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation) all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down some of the mentioned uncertainties. Water column concentrations of particulate and dissolved organic and inorganic constituents were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution, as well as estimates of wall growth were developed to close the gaps in element budgets. Future elevated pCO2 was found to enhance net autotrophic community carbon uptake in 2 of the 3 experimental phases but did not significantly affect particle elemental composition. Enhanced carbon consumption appears to result in accumulation of dissolved organic compounds under nutrient recycling summer conditions. This carbon over-consumption effect becomes evident from budget calculations, but was too small to be resolved by direct measurements of dissolved organics. The out-competing of large diatoms by comparatively small algae in nutrient uptake caused reduced production rates under future ocean CO2 conditions in the end of the experiment. This CO2 induced shift away from diatoms towards smaller phytoplankton and enhanced cycling of dissolved organics was pushing the system towards a retention type food chain with overall negative effects on export potential. [ABSTRACT FROM AUTHOR]

The Arctic Ocean is a unique marine environment with respect to seasonality of light, temperature, perennial ice cover and strong stratification. Other important distinctive features are the influence of extensive continental shelves and its interactions with Atlantic and Pacific water masses and freshwater from sea ice melt and rivers. These characteristics have major influence on the biological and biogeochemical processes occurring in this complex natural system. Heterotrophic bacteria are crucial components of marine food webs and have key roles in controlling carbon fluxes in the oceans. Although it was previously thought that these organisms relied on the organic carbon in seawater for all of their energy needs, several recent discoveries now suggest that pelagic bacteria can depart from a strictly heterotrophic lifestyle by obtaining energy through unconventional mechanisms that are linked to the penetration of sunlight into surface waters. These photoheterotrophic mechanisms may play a significant role in the energy budget in the euphotic zone of marine environments. We can suspect that this role could be of greater importance in the Arctic Ocean where environmental changes triggered by climate change could favor the photoheterotrophic lifestyle. Here we review advances in our knowledge of the diversity of marine photoheterotrophic bacteria and discuss their significance in the Arctic Ocean gained in the framework of the Malina cruise. [ABSTRACT FROM AUTHOR]

The Arctic Ocean accounts for only 4% of the global ocean area but it contributes significantly to the global carbon cycle. Recent observations of seawater carbonate chemistry in shelf waters of the Western Arctic from 2009 to 2011 indicate that extensive areas of the benthos are exposed to bottom waters that are seasonally undersaturated with respect to calcium carbonate (CaCO3) minerals, particularly aragonite. Our observations indicate seasonal reduction of saturation states (ω) for calcite (ωcalcite) and aragonite (ωaragonite) in the subsurface in the Western Arctic by as much as 0.9 and 0.6, respectively. Such data indicates that bottom waters of the Western Arctic shelves are already potentially corrosive for biogenic and sedimentary CaCO3 for several months each year. Seasonal changes in ω are imparted by a variety of factors such as phytoplankton photosynthesis, respiration/remineralization of organic matter and air-sea gas exchange of CO2 - combined these processes either increase or enhance ω in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA) on ω in surface and subsurface waters, respectively. Future monitoring of the Western Arctic shelves is warranted to assess the present and future impact on ω values from ocean acidification and seasonal biological/physical processes on Arctic marine ecosystems. [ABSTRACT FROM AUTHOR]

A drastic ice decline in the Arctic Ocean, triggered by global warming, could generate rapid changes in the upper ocean layers. The ice retreat is particularly intense over the Canadian Basin where large ice free areas were observed since 2007. The CHINARE 2008 expedition was conducted in the Western Arctic (WA) ocean during a year of exceptional ice retreat (August-September 2008). This study investigates whether a significant reorganization of the primary producers in terms of species, biomass and productivity has to be observed in the WA as a result of the intense ice melting. Both pigments (HPLC) and taxonomy (microscopy) acquired in 2008 allowed to determine the phytoplanktonic distribution from Bering Strait (65° N) to extreme high latitudes over the Alpha Ridge (86° N) encompassing the Chukchi shelf, the Chukchi Borderland and the Canadian Basin. Two different types of phytoplankton communities were observed. Over the ice-free Chukchi shelf, relatively high chl-a concentrations (1-5mgm-3) dominated by 80% of diatoms. In the Canadian Basin, surface waters are oligotrophic (<0.1mgm-3) and alal assemblages were dominated by haptophytes and diatoms while higher biomasses (~0.4mgm-3) related to a deep Subsurface Chlorophyll Maximum (SCM) are associated to small-sized (nano and pico) phytoplankton. The ice melting onset allows to point out three different zones over the open basin: (i) the ice free condition characterized by deep and unproductive phytoplankton communities dominated by nanoplankton, (ii) an extended (78°-83° N) Active Melting Zone (AMZ) where light penetration associated to the stratification start off and enough nutrient availability drives to the highest biomass and primary production due to both diatoms and large flagellates, (iii) heavy ice conditions found north to 83° N allowing light limitation and consequently low biomass and primary production associated to pico and nanoplankton. To explain the poverty (Canadian Basin) and the richness (Chukchi shelf) of the WA, we explore the role of the nutrient-rich Pacific Waters, the bathymetry and two characteristics linked to the intense ice retreat: the stratification and the Surface Freshwater [ABSTRACT FROM AUTHOR]

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), C/N and CaCO3 from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on correlation of our CaCO3 record with the benthic δ18O stack, supplemented by lithological constraints, suggests that the piston core records paleoenvironmental changes of the last 155 kyr. According to this age model, TOC and C/N show orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC and C/N appear to correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 40 ka before present (BP) and thus seem to respond to abrupt northern hemispheric temperature changes. Between 65 and 40 kaBP, closures and openings of the Bering Strait could have additionally influenced TOC and C/N variability. CaCO3 content tends to anti-correlate with TOC and C/N on both orbital and millennial time scales, which we interpret as enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased terrestrial organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation. [ABSTRACT FROM AUTHOR]

In this paper we explore how post-petroleum security is continually shaped by both the micropolitical practices of everyday life as well as the changing geopolitics of energy landscapes. We focus in particular on the two-decade long struggle over access to hydrocarbon deposits outside the Lofoten, Vesterålen and Senja archipelago groups (LoVeSe), and show how local security perspectives permeate both national and international debates concerning the future of oil and the global climate challenge. These developments, we argue, are taking place in a paradoxical conjunction with Norwegian political establishment who along with the oil and gas industry insist on continued petroleum dependency as the only viable future. We further investigate how particular controlling measures have determined past, present and future narratives, and assess how alternative ideas that include multiple possible trajectories have found their way into national and global debates despite these efforts. The argument permeating this paper states that while oil remains a security concern to both proponents and opponents to oil development in the Arctic, the extent to which this situation is seen as a threat or a security provider varies greatly. [ABSTRACT FROM AUTHOR]

This paper discusses the state of the Arctic cryosphere during the second half of the twentieth century and describes major findings of observational evidence since the 1950s. Although glaciers have been retreating steadily from their Little Ice Age maximum positions for decades, Arctic sea ice extent and thickness began to decline and loss of mass from the Greenland ice sheet accelerated only in the 1990s. Rapid changes in cryospheric components have occurred in this century, affecting snow cover, Arctic sea ice extent, the mass balance of the Greenland ice sheet, and frozen ground temperatures. Projections for this century, based on model results from the Intergovernmental Panel on Climate Change, involve dramatic changes by 2100. [ABSTRACT FROM AUTHOR]

Abstract As the Arctic continues to warm, summer sea ice will continue to recede and a greater expanse of Arctic waters will become navigable. These changes may result in an increase in vessel traffic to the region, including via the Transpolar Sea Route (TSR), through the high seas area of the central Arctic Ocean (CAO). This paper begins with a review of the literature on Arctic vessel traffic to assess the potential effects of various stressors related to vessel traffic in the Arctic Ocean. Available data concerning environmental and safety risks for the Arctic Ocean are used to propose vessel TSR vessel traffic routes that can reduce those risks. The paper concludes with a brief discussion of several examples of vulnerability assessments focused on impacts from vessel traffic in the Arctic as potential models for future work specific to the CAO. The results from this review indicate vessel oiling, air pollution, and noise from icebreakers are immediate concerns to the Arctic Ocean that will likely worsen as the region becomes more navigable and vessel traffic increases. The proposed vessel routes for the Arctic Ocean are meant to serve as a starting point for further discussions before the region becomes fully navigable. As additional data become available, these efforts can be refined further, and a rigorous vulnerability assessment may become possible. Designation as a Particularly Sensitive Sea Area under international law could provide a useful mechanism for creating and updating precautionary shipping measures as more information becomes available. [ABSTRACT FROM AUTHOR]

The impact of climate change on the circumpolar north has raised the profile of the Arctic Ocean to coastal states and presents serious foreign policy challenges. Chief among these is the pending delimitation dispute over the extended continental shelf between Canada, Denmark, the United States, and Russia. While delimitation disputes are not new to Arctic states, extended continental shelf claims are complicated by the existence of multiple claimants and a still developing international legal regime. To inform policymakers about what to expect from overlapping claims to disputed maritime areas, this paper draws comparative lessons for Arctic policymakers based on East Asia's experience responding to overlapping jurisdictional entitlements created by the UN Convention on the Law of the Sea (UNCLOS). East Asian states have been grappling with the challenge presented by overlapping claims to resource-rich seabeds since the region ratified UNCLOS in the mid-late 1990s. In light of similar geographic conditions (a dispute over a semi-enclosed sea), alliance structures and the relative infancy of the claimant states with UNCLOS entitlements-Canada only ratified the treaty in 2003, and the United States has yet to do so-this paper sets out the case that important comparative lessons can be drawn from the East Asian experience with maritime delimitation disputes. [ABSTRACT FROM AUTHOR]

The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-atmosphere-aquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context. [ABSTRACT FROM AUTHOR]

The sedimentation rate is one of the most important facies parameters in sedimentation basins, including seas and oceans. This paper presents a review of available data on the average sedimentation rates for the last five marine isotope stages (last 130 kyr) in the Arctic Ocean (with exception of shelves). We have revealed the sharply expressed circumcontinental zonality and asymmetry in the distribution of the above-mentioned parameter. The influence of the solid discharge structure, oceanic circulation, ice conditions, climatic fluctuations, and bottom topography on the sedimentation rate is considered. [ABSTRACT FROM AUTHOR]

Understanding of past climate variability on millennial to decadal scales are of primary importance in order to assess modern processes and predict future climatic events. Past history of Arctic climate changes is currently receiving increasing attention due to the recent phenomena of rapid sea-ice reduction. In this paper, we thoroughly reviewed the Holocene history of spatiotemporal climatic changes in the western Arctic region in order to better understand recent rapid environmental changes occurring in the Pacific sector of the Arctic, and further to discuss critical issues and new perspectives on the western Arctic in terms of paleoclimate researches. Records of temporal and spatial variations in sea-ice extents as well as marine and terrestrial paleoclimatic proxies show a strong asynchronicity between the western and eastern Arctic throughout the Holocene. The reason for this apparent contradiction across the Arctic may be linked to freshwater discharges over the Arctic shelves and the inflow of the Pacific freshwater into the western Arctic Ocean in coupled with a complex interaction between atmospheric and sea-ice dynamics. Special emphasis is placed on a tentative linkage of the late Holocene paleoclimatic events between the Arctic regions and the northwestern Pacific margin, highlighting the notion that climatic events of the northern Pacific Ocean is closely linked to the global climate system through hydrological dynamics in the western Arctic Ocean. [ABSTRACT FROM AUTHOR]

In this paper we describe sea ice change and variability during the Canadian International Polar Year (IPY) program and examine several regional and hemispheric causes of this change. In a companion paper (Barber et al., Climate Change) we present an overview of the consequences of this observed change and variability on ecosystem function, climatically relevant gas exchange, habitats of primary and apex predators, and impacts on northern peoples. Sea ice-themed research projects within the fourth IPY were designed to be among the most diverse international science programs. They greatly enhanced the exchange of Inuit knowledge and scientific ideas across nations and disciplines. This interdisciplinary and cultural exchange helped to explain and communicate the impacts of a transition of the Arctic Ocean and ecosystem to a seasonally ice-free state, the commensurate replacement of perennial with annual sea ice types and the causes and consequences of this globally significant metamorphosis. This paper presents a synthesis of scientific sea ice research and traditional knowledge results from Canadian-led IPY projects between 2007 and 2009. In particular, a summary of sea ice trends, basin-wide and regional, is presented in conjunction with Inuit knowledge of sea ice, gathered from communities in northern Canada. We focus on the recent observed changes in sea ice and discuss some of the causes of this change including atmospheric and oceanic forcing of both dynamic and thermodynamic forcing on the ice. Pertinent results include: 1) In the Amundsen Gulf, at the western end of the Northwest Passage, open water persists longer than normal and winter sea ice is thinner and more mobile. 2) Large areas of summer sea ice are becoming heavily decayed during summer and can be broken up by long-period waves being generated in the now extensive open water areas of the Chukchi Sea. 3) Cyclones play an important role in flaw leads-regions of open water between pack ice and land-fast ice. They delay the formation of new ice and the growth of multi-year ice. 4) Feedbacks involving the increased period of open water, long-period wave generation, increased open-ocean roughness, and the precipitation of autumn snow are all partially responsible for the observed reduction in multiyear sea ice. 5) The atmosphere is observed as remaining generally stable throughout the winter, preventing vertical entrainment of moisture above the surface. [ABSTRACT FROM AUTHOR]

The article presents the biometeorological impact of thermal and humidity conditions on the human body in the Hornsund area in the southern Spitsbergen, Svalbard. This was determined based on diurnal air temperature range, the day-to-day variation in average diurnal air temperature and the average diurnal relative humidity. The temporal variability of thermal and humidity biometeorological stimuli in Hornsund was examined for the period 01.11.1978-31.12.2017. A lessening of biometeorological impact was found in the southern Spitsbergen region, including a statistically significant negative trend in strongly- and severely-felt stimuli (according to diurnal air temperature range), and in significant and severe stimuli (according to day-to-day variation in average diurnal air temperature). A non-significant positive trend was observed in the number of days of relative humidity with humid and very humid air. To analyse the spatial variability of the stimuli around the Hornsund fjord, data were used from seven year-round measuring stations for the period 01.07.2014-31.06.2015. The most unfavourable conditions were found on the Hans Glacier, on the summit of Fugleberget and inside the fjord. The paper presents the role of atmospheric circulation on thermal and humidity stimuli. In the Hornsund region, the highest probability of unfavourable sensible temperatures for humans occurring during the year was mostly in winter and early spring. This was related to the advection of air masses from the north-east sector, regardless of baric regime type. It was found that very humid air (> 85%) flowed over Hornsund for practically the entire year from the S-SW as part of both cyclonic and anti-cyclonic systems. [ABSTRACT FROM AUTHOR]

This paper surveys matters related to the need for a new legal regime for the Arctic Ocean. It reviews the legal system based on the UN Convention for the Law of the Sea, and the regional and international treaties dealing with resource management, (marine) environmental protection and economic activities applicable to the Arctic. It suggests that implementation of existing legal instruments at the domestic level is a key factor needed to tackle the consequences of climate change and governance of fisheries and marine ecosystems in the Arctic. It is also considered to be the Arctic Council's responsibility to build a common understanding among the stakeholders, thereby enhancing the potential for further international cooperation. [ABSTRACT FROM AUTHOR]

Downwelling radiation in six regional models from the Arctic Regional Climate Model Intercomparison (ARCMIP) project is systematically biased negative in comparison with observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, although the correlations with observations are relatively good. In this paper, links between model errors and the representation of clouds in these models are investigated. Although some modeled cloud properties, such as the cloud water paths, are reasonable in a climatological sense, the temporal correlation of model cloud properties with observations is poor. The vertical distribution of cloud water is distinctly different among the different models; some common features also appear. Most models underestimate the presence of high clouds, and, although the observed preference for low clouds in the Arctic is present in most of the models, the modeled low clouds are too thin and are displaced downward. Practically all models show a preference to locate the lowest cloud base at the lowest model grid point. In some models this happens also to be where the observations show the highest occurrence of the lowest cloud base; it is not possible to determine if this result is just a coincidence. Different factors contribute to model surface radiation errors. For longwave radiation in summer, a negative bias is present both for cloudy and clear conditions, and intermodel differences are smaller when clouds are present. There is a clear relationship between errors in cloud-base temperature and radiation errors. In winter, in contrast, clear-sky cases are modeled reasonably well, but cloudy cases show a very large intermodel scatter with a significant bias in all models. This bias likely results from a complete failure in all of the models to retain liquid water in cold winter clouds. All models overestimate the cloud attenuation of summer solar radiation for thin and intermediate clouds, and some models maintain this behavior also for thick clouds. [ABSTRACT FROM AUTHOR]

This paper analyzes regional sea level changes in a climate change simulation using the Max Planck Institute for Meteorology (MPI) coupled atmosphere–ocean general circulation model ECHAM5/MPI-OM. The climate change scenario builds on observed atmospheric greenhouse gas (GHG) concentrations from 1860 to 2000, followed by the International Panel on Climate Change (IPCC) A1B climate change scenario until 2100; from 2100 to 2199, GHG concentrations are fixed at the 2100 level. As compared with the unperturbed control climate, global sea level rises 0.26 m by 2100, and 0.56 m by 2199 through steric expansion; eustatic changes are not included in this simulation. The model’s sea level evolves substantially differently among ocean basins. Sea level rise is strongest in the Arctic Ocean, from enhanced freshwater input from precipitation and continental runoff, and weakest in the Southern Ocean, because of compensation of steric changes through dynamic sea surface height (SSH) adjustments. In the North Atlantic Ocean (NA), a complex tripole SSH pattern across the subtropical to subpolar gyre front evolves, which is consistent with a northward shift of the NA current. On interannual to decadal time scales, the SSH difference between Bermuda and the Labrador Sea correlates highly with the combined baroclinic gyre transport in the NA but only weakly with the meridional overturning circulation (MOC) and, thus, does not allow for estimates of the MOC on these time scales. Bottom pressure increases over shelf areas by up to 0.45 m (water column equivalent) and decreases over the Atlantic section in the Southern Ocean by up to 0.20 m. The separate evaluation of thermosteric and halosteric sea level changes shows that thermosteric anomalies are positive over most of the World Ocean. Because of increased atmospheric moisture transport from low to high latitudes, halosteric anomalies are negative in the subtropical NA and partly compensate thermosteric anomalies, but are positive in the Arctic Ocean and add to thermosteric anomalies. The vertical distribution of thermosteric and halosteric anomalies is highly nonuniform among ocean basins, reaching deeper than 3000 m in the Southern Ocean, down to 2200 m in the North Atlantic, and only to depths of 500 m in the Pacific Ocean by the end of the twenty-first century. [ABSTRACT FROM AUTHOR]

Observed reduction in recent sea ice areal extent and thickness has focused attention on the fact that the Arctic marine system appears to be responding to global-scale climate variability and change. Passive microwave remote-sensing data are the primary source underpinning these reports, yet problems remain in geophysical inversion of information on ice type and concentration. Uncertainty in sea-ice concentration (SIC) retrievals is highest in the summer and fall, when water occurs in liquid phase within the snow-sea-ice system. Of particular scientific interest is the timing and rate of new ice formation due to the control that this form of sea ice has on mass, energy and gas fluxes across the ocean-sea-ice-atmosphere interface. In this paper we examine the critical fall freeze-up period using in situ data from a ship-based and aerial survey programme known as the Canadian Arctic Shelf Exchange study combined with microwave and optical Earth observations data. Results show that: (1) the overall physical conditions observed from aerial survey photography were well matched with coincident moderate-resolution imaging spectroradiometer data and Radarsat ScanSAR imagery; (2) the shortwave albedo was linearly related to old ice concentration derived from survey photography; (3) the three SSM/I SIC algorithms (NASA Team (NT), NASA Team 2 (NT2), and Bootstrap (BT)) showed considerable discrepancies in pixel-scale comparison with the Radarsat ScanSAR SICs well calibrated by the aerial survey data. The major causes of the discrepancies are attributed to (1) the inherent inability to detect the new thin ice in the NT and BT algorithms, (2) mismatches of the thin-ice tie point of the NT2 algorithm, and (3) sub-pixel ambiguity between the thin ice and the mixture of open water and sea ice. These results suggest the need for finer resolution of passive microwave sensors, such as AMSR-E, to improve the precision of the SSM/I SIC algorithms in the marginal ice zone during early fall freeze-up. [ABSTRACT FROM AUTHOR]

Changes in Arctic sea ice cover have the potential to impact midlatitude climate. A previous sensitivity study utilizing the National Center for Atmospheric Research¿s (NCAR) atmospheric general circulation model [AGCM; Community Climate Model, version 3 (CCM3)] to explore climate sensitivity to declining Arctic sea ice cover suggested that, as Arctic sea ice cover is reduced, precipitation patterns over western North America will shift toward dryer conditions in southwestern North America and wetter conditions in northwestern North America. Here, three complementary lines of research validate and explore the robustness of this possible climate change impact: 1) repetition of the previous sensitivity study (specified constant Arctic sea ice cover and atmospheric CO2) with an updated version of the NCAR AGCM [third Community Atmosphere Model (CAM3)], 2) investigation of the climate response to dynamically reduced Arctic sea ice cover (driven by a quadrupling of atmospheric CO2) in the coupled NCAR Community Climate System Model (CCSMv3), and 3) analysis of similar results from six other coupled climate system models. Results from the CAM3 sensitivity study are similar to those from the original study with declining Arctic sea ice cover driving up to 25% less mean annual precipitation (MAP) over southwestern North America and up to an 8% increase in MAP over northwestern North America. The seven coupled models also reproduce this same general pattern. At the time of CO2 quadrupling, Arctic sea ice cover is reduced (up to 90% in boreal winter) and MAP over southwestern North America decreases by up to 30% while MAP in northwestern North America increases by up to 40%. These results represent a significant shift in the precipitation pattern over western North America and support the findings of the original sensitivity study in suggesting that, as future reductions in Arctic sea ice cover take place, there will be a substantial impact on water resources in western North America. [ABSTRACT FROM AUTHOR]

Planktic foraminifers can be sensitive indicators of the changing environment including both the Arctic Ocean and Southern Ocean. Due to variability in their ecology, biology, test characteristics, and fossil preservation in marine sediments, they serve as valuable archives in paleoceanography and climate geochemistry over the geologic time scale. Foraminifers are sensitive to, and can therefore provide proxy data on ambient water temperature, salinity, carbonate chemistry, and trophic conditions through shifts in assemblage (species) composition and the shell chemistry of individual specimens. Production and dissolution of the calcareous shell, as well as growth and remineralization of the cytoplasm, affect the carbonate counter pump and to a lesser extent the soft-tissue pump, at varying regional and temporal scales. Diversity of planktic foraminifers in polar waters is low in comparison to lower latitudes and is limited to three native species: Neogloboquadrina pachyderma , Turborotalita quinqueloba , and Globigerina bulloides , of which N. pachyderma is best adapted to polar conditions in the surface ocean. Neogloboquadrina pachyderma hibernates in brine channels in the lower layers of the Antarctic sea ice, a strategy that is presently undescribed in the Arctic. In open Antarctic and Arctic surface waters T. quinqueloba and G. bulloides increase in abundance at lower polar to subpolar latitudes and Globigerinita uvula , Turborotalita humilis , Globigerinita glutinata , Globorotalia inflata , and Globorotalia crassaformis complement the assemblages. Over the past two to three decades there has been a marked increase in the abundance of Orcadia riedeli and G. uvula in the subpolar and polar Indian Ocean, as well as in the northern North Atlantic. This paper presents a review of the knowledge of polar and subpolar planktic foraminifers. Particular emphasis is placed on the response of foraminifers to modern warming and ocean acidification at high latitudes and the implications for data interpretation in paleoceanography and paleoclimate research. [ABSTRACT FROM AUTHOR]

This paper describes the development and validation of a method to accurately identify snow/ice cover, surface melting, land surface and open water in polar regions using polar-orbiting Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar measurements from the Cloud and Aerosol Lidar and Infrared Pathfinder Observation (CALIPSO) mission. The technique is based on the relationship between integrated attenuated backscatter color ratio and integrated depolarization ratio, and is proven to efficiently separate snow/ice cover and surface melting from open water and land surfaces. The method has been applied to 10 years (2006–2016) of CALIOP data to study the seasonal and inter-annual variability of Arctic sea ice cover and its declining trend. Results show that the area fraction of snow cover over land at latitudes > 60°N varied between 0.9 during winter and 0.1 in summer. The CALIOP observations of Arctic sea ice cover exhibit a strong seasonal cycle and significant inter-annual variability, which are consistent with the passive microwave-based sea ice results. The > 10 years of CALIOP continuous observations of the snow/ice cover will benefit the communities modeling snow/ice melting and climate change. [ABSTRACT FROM AUTHOR]

Abstract: Arctic coastal populations share a close relationship with their environment consisting of linkages among communities, landscapes and seascapes, and the social institutions developed to sustain the system. This cultural–biogeophysical dynamic is termed throughout the section as a social–ecological system (SES). Marine mammals constitute a large portion of the subsistence diet for these communities, and as such represent key ecological services provided by the system. At the same time, marine mammals have gained iconic status as symbols for climate change in the North. A tension results between the demands of balancing on one hand good policy optics consistent with national and international norms and, on the other hand, flexible and adaptive institutions able to take on the task of managing resources in a dynamic, changing North. This tension and associated policy solutions such as co-management are explored in a series of papers focusing on marine mammal management dilemmas and policy practices around the circumpolar North. This introduction communicates the problem context and describes the five papers making up this special section. A guiding premise to this work is that new international pressures to implement moratoria on marine mammal hunting in the North ignore critical human dimensions of marine mammal management. Such policy proposals are unlikely to succeed in areas that require collaboration across scales. Simultaneously, new local-scale participation in multi-level management regimes holds promise for creating more resilient marine mammal SESs. [Copyright &y& Elsevier]

We demonstrate for the first time a direct oceanic link between climate‐driven change in the North Atlantic and Arctic Oceans and the circulation of the northwest European shelf seas. Downscaled scenarios show a shutdown of the exchange between the Atlantic and the North Sea and a substantial decrease in the circulation of the North Sea in the second half of the 21st century. The northern North Sea inflow decreases from 1.2–1.3 Sv (1 Sv = 106 m3/s) to 0.0–0.6 Sv with Atlantic water largely bypassing the North Sea. This is traced to changes in oceanic haline stratification and gyre structure and to a newly identified circulation‐salinity feedback. The scenario presented here is of a novel potential future state for the North Sea, with wide‐ranging environmental management and societal impacts. Specifically, the sea would become more estuarine and susceptible to anthropogenic influence with an enhanced risk of coastal eutrophication. Plain Language Summary: Little is known about how climate change might impact the long‐term circulation of shelf seas. In this paper, we use a high‐resolution shelf sea model to demonstrate how end‐of‐century changes in the wider ocean can lead to a substantial reduction in the flow of water from the North Atlantic into the North Sea. This, in turn, reduces the circulation of this sea, which becomes more influenced by rivers and less by oceanic waters. River water generally contains higher levels of nutrients, and our simulations show that this future scenario leads to enhanced levels of phytoplankton growth in local regions of the North Sea. This may lead to undesirable disturbances to the marine ecosystems, such as depletion of oxygen near the seabed. The reduced circulation would also disrupt the transport of larvae around the sea and lead to increased retention of pollutants. The reduction in circulation arises from several causes relating to increased density layering at the continental shelf edge, changes in the large‐scale ocean circulation and salinity, and disruption of the density‐driven circulation of the North Sea. By exploring these novel future scenarios, we emphasize the need to understand better the many ways climate change can influence the marine environment and its ecosystems. Key Points: Potential end‐of‐century scenarios of dramatically reduced North Sea inflow and circulation are demonstrated by downscaling experimentsThis reduction is traced to increased shelf‐slope salinity stratification and modified North Atlantic and Arctic circulation and salinityThe North Sea then becomes more estuarine, with some regions of substantially enhanced nutrient content and primary production [ABSTRACT FROM AUTHOR]

The early 19th century was the coldest period over the past 500 years, when strong tropical volcanic events and a solar minimum coincided. The 1809 unidentified eruption and the 1815 Tambora eruption happened consecutively during the Dalton minimum of solar irradiance; however, the relative role of the two forcing (volcano and solar) agents is still unclear. In this study, we examine the effects from combinations of one volcanic with two different solar forcing reconstructions (SATIRE and PMOD) suggested in the protocol for the past1000 experiment of the Paleoclimate Modelling Intercomparison Project – Phase 4 (PMIP4) by simulating the early 19th century climate. From 20-member ensemble simulations with the Max Planck Institute Earth System Model (MPI-ESM1.2-LR), we find that the volcano- and solar-induced surface cooling is in general additive, regardless of combining or separating the forcing agents. The two solar reconstructions (SATIRE and PMOD) contribute on average ~0.05 K/month and ~0.15 K/month surface air cooling, respectively, indicating a limited solar contribution to the early 19th century cold period. The volcanic events provide the main cooling contributions, inducing a surface cooling peak of ~0.82 K for the 1809 event and ~1.35 K for Tambora. After the Tambora eruption, the cooling in most regions reduces largely within 5 years when a global cooling of ~0.34 K is reached, along with the reduction of volcanic forcing. In the northern extratropical oceans, the cooling reduces only slowly with a constant rate until 1830, which is related to the reduction of seasonality and the increased Arctic sea-ice extent. Also, the albedo feedback of Arctic sea ice is found to be the main contributor to the Arctic amplification of the cooling signal. Several non-additive responses to solar and volcanic forcing happen on regional scales. In the atmosphere, the polar vortex tends to strengthen when combining both volcano and solar forcing, even though the two forcing agents separately induce opposite responses. In the ocean, when combining the two forcings, additional surface cold water propagates to the northern extra-tropics from the additional solar cooling in the tropics, which results in regional cooling along the propagation. Overall, this study not only quantifies the surface responses from combinations of volcano and solar forcing, but also highlights the components that cannot be simply added from the responses of the individual forcing agents, indicating that a relatively small forcing agent (such as solar in early 19th century) can impact the response from the large forcing (such as the Tambora eruption) when considering regional climates. [ABSTRACT FROM AUTHOR]

The article evaluates on whether Canada’s regulatory scheme for protecting Arctic waters operate within the parameters of Article 234 of the Law of the Sea convention. Topics of discussion includes the scope of Article 234 and its explanation, summary of Canada’s Arctic waters regime and inconsistencies with the article 234.

Precipitation changes projected for the end of the twenty-first century show an increase of more than 50 per cent in the Arctic regions. This marked increase, which is among the highest globally, has previously been attributed primarily to enhanced poleward moisture transport from lower latitudes. Here we use state-of-the-art global climate models to show that the projected increases in Arctic precipitation over the twenty-first century, which peak in late autumn and winter, are instead due mainly to strongly intensified local surface evaporation (maximum in winter), and only to a lesser degree due to enhanced moisture inflow from lower latitudes (maximum in late summer and autumn). Moreover, we show that the enhanced surface evaporation results mainly from retreating winter sea ice, signalling an amplified Arctic hydrological cycle. This demonstrates that increases in Arctic precipitation are firmly linked to Arctic warming and sea-ice decline. As a result, the Arctic mean precipitation sensitivity (4.5 per cent increase per degree of temperature warming) is much larger than the global value (1.6 to 1.9 per cent per kelvin). The associated seasonally varying increase in Arctic precipitation is likely to increase river discharge and snowfall over ice sheets (thereby affecting global sea level), and could even affect global climate through freshening of the Arctic Ocean and subsequent modulations of the Atlantic meridional overturning circulation. [ABSTRACT FROM AUTHOR]

Abstract: To better understand Pleistocene climatic changes in the Arctic, integrated palaeoenvironmental and palaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologic age control are required, not least for correlation to extra-Arctic records. In this paper we discuss, from an Arctic perspective, methods and correlation tools that are commonly used to date Arctic Pleistocene marine and terrestrial events. We review the state of the art of Arctic geochronology, with focus on factors that affect the possibility and quality of dating, and support this overview by examples of application of modern dating methods to Arctic terrestrial and marine sequences. Event stratigraphy and numerical ages are important tools used in the Arctic to correlate fragmented terrestrial records and to establish regional stratigraphic schemes. Age control is commonly provided by radiocarbon, luminescence or cosmogenic exposure ages. Arctic Ocean deep-sea sediment successions can be correlated over large distances based on geochemical and physical property proxies for sediment composition, patterns in palaeomagnetic records and, increasingly, biostratigraphic data. Many of these proxies reveal cyclical patterns that provide a basis for astronomical tuning. Recent advances in dating technology, calibration and age modelling allow for measuring smaller quantities of material and to more precisely date previously undatable material (i.e. foraminifera for 14C, and single-grain luminescence). However, for much of the Pleistocene there are still limits to the resolution of most dating methods. Consequently improving the accuracy and precision (analytical and geological uncertainty) of dating methods through technological advances and better understanding of processes are important tasks for the future. Another challenge is to better integrate marine and terrestrial records, which could be aided by targeting continental shelf and lake records, exploring proxies that occur in both settings, and by creating joint research networks that promote collaboration between marine and terrestrial geologists and modellers. [Copyright &y& Elsevier]

Climate change is especially strong in the region of the Arctic Ocean, and will have an important impact on its thermo‐haline structure. We analyze the results of a hindcast simulation of a new 3D ocean model of the Arctic and North Atlantic oceans for the period 1970–2019. We compared the time period 1970–1999 with the time period 2010–2019. The comparison showed that there is a decrease of stratification between the two periods over most of the shallow Arctic shelf seas and in the core of the Transpolar Ice Drift. Fresh water inputs to the ocean surface decline, and inputs of momentum to the ocean increase, which can explain the decrease in stratification. The comparison also showed that the mixed layer becomes deeper during winter, in response to the weakened stratification owing to increased vertical mixing. The comparison of summer mixed layer depths between the two time periods follows a deepening pattern that is less evident. Regional exceptions include the Nansen Basin and the part of the Canadian Basin bordering the Canadian Archipelago, where the mixed layer shoals. Trends of freshwater fluxes imply that the changes of haline stratification in these regions are also influenced by other processes, for example, horizontal advection of fresh water, increased mixing and changes in the underlaying water masses. Runoff increase toward the Arctic Ocean can locally decrease but also increase salinity, and has an impact on stratification which can be explained by coastal dynamics. The results emphasize the non‐linear nature of Arctic Ocean dynamics. Plain Language Summary: We analyzed the results of an ocean model simulation for the Arctic and North Atlantic oceans for the period 1970–2019. Our model is in line with the recent observed changes in the Arctic Ocean and allows, in contrast to the rather sparse observations, a detailed assessment of stratification changes. These changes will affect the Arctic ecosystem and are also believed to affect the large scale ocean circulation. We show that major changes in upper ocean conditions are caused by changes in the fresh water supply by sea ice and varying effect of the wind on regions that are now becoming ice‐free. We also study the effect of changes in river runoff into the Arctic Ocean. Our study shows that an increase in river runoff can change the coastal circulation and results, paradoxically, in regions of higher salinity. These results point to the importance of modeling tools when it comes to a better understanding of ocean processes in a changing climate. Key Points: Results from a hindcast simulation of the Arctic Ocean for the period 1970–2019 show strong changes in stratificationThe changes in stratification are explained by altered surface stress and freshwater fluxesTrends in river runoff have little effect on the mixed layer depth but change the Arctic coastal circulation [ABSTRACT FROM AUTHOR]

Abstract: Recent warming of surface waters, accompanied by reduced ice thickness and extent may have significant consequences for climate-driven changes of primary production (PP) in the Arctic Ocean (AO). However, it has been difficult to obtain a robust benchmark estimate of pan-Arctic PP necessary for evaluating change. This paper provides an estimate of pan-Arctic PP prior to significant warming from a synthetic analysis of the ARCSS-PP database of in situ measurements collected from 1954 to 2007 and estimates derived from satellite-based observations from 1998 to 2007. Vertical profiles of in situ chlorophyll a (Chl a) and PP revealed persistent subsurface peaks in biomass and PP throughout the AO during most of the summer period. This was contradictory with the commonly assumed exponential decrease in PP with depth on which prior satellite-derived estimates were based. As remotely sensed Chl a was not a good predictor of integrated water column Chl a, accurate satellite-based modeling of vertically integrated primary production (IPPsat), requires knowledge of the subsurface distribution of phytoplankton, coincident with the remotely sensed ocean color measurements. We developed an alternative approach to modeling PP from satellite observations by incorporating climatological information on the depths of the euphotic zone and the mixed layer that control the distribution of phytoplankton that significantly improved the fidelity of satellite derived PP to in situ observations. The annual IPP of the Arctic Ocean combining both in situ and satellite based estimates was calculated here to be a minimum of 466±94TgCyr−1 and a maximum of 993±94TgCyr−1, when corrected for subsurface production. Inflow shelf seas account for 75% of annual IPP, while the central basin and Beaufort northern sea were the regions with the lowest annual integrated productivity, due to persistently stratified, oligotrophic and ice-covered conditions. Although the expansion of summertime ice retreat should stimulate photosynthesis by exposing more of the AO to solar irradiance, total PP is ultimately limited by nutrient availability. Therefore, changes in AO PP will be forced by the balance between stratification and mixing, the effects of which are not yet quantified. [Copyright &y& Elsevier]

The variations of climate with periods within the narrow-banded range from 60 up to 70 years are considered. The existence of climate variations with these periods is proved by time-frequency spectral analysis of scalar time series and by joint multiple spectral analysis of 3 well-known synchronous climatic time series covering the time interval 553-1973. Prediction of global temperature anomaly dT based on applying cyclic trend with period 66 years was made for the future time interval of the length 20 years. The main peculiarity of this prediction is the decreasing of global dT (i.e. global cooling instead of global warming) which started at 2008 and will be continuing during 2011-2030. Estimates of cyclic trends for temperature anomalies of North and South hemispheres separately give periods 69 and 63 years correspondently. These results are based on using of dT data for time interval 1850-2010. They confirm the earlier results of authors which was published at 2003 about starting the global cooling process at 2008. If the global cooling cyclic trend for nearest 20 years will be approved this will have a serious consequences in changing of global energetic politics. For example, extensive plans about using Arctic resources in the near future, as is now frequently announced by governments in connection with the melting ice cover of the Arctic Ocean, are out of question. [ABSTRACT FROM AUTHOR]

Climate models vary widely in their projections of both global mean temperature rise and regional climate changes, but are there any systematic differences in regional changes associated with different levels of global climate sensitivity? This paper examines model projections of climate change over the twenty-first century from the Intergovernmental Panel on Climate Change Fourth Assessment Report which used the A2 scenario from the IPCC Special Report on Emissions Scenarios, assessing whether different regional responses can be seen in models categorized as ‘high-end’ (those projecting 4°C or more by the end of the twenty-first century relative to the preindustrial). It also identifies regions where the largest climate changes are projected under high-end warming. The mean spatial patterns of change, normalized against the global rate of warming, are generally similar in high-end and ‘non-high-end’ simulations. The exception is the higher latitudes, where land areas warm relatively faster in boreal summer in high-end models, but sea ice areas show varying differences in boreal winter. Many continental interiors warm approximately twice as fast as the global average, with this being particularly accentuated in boreal summer, and the winter-time Arctic Ocean temperatures rise more than three times faster than the global average. Large temperature increases and precipitation decreases are projected in some of the regions that currently experience water resource pressures, including Mediterranean fringe regions, indicating enhanced pressure on water resources in these areas. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a validation study performed by comparing the Climate-SAF Surface Albedo Product (SAL) to ground truth observations over Greenland and the ice-covered Arctic Ocean. We compare Advanced Very High Resolution Radiometer (AVHRR)-based albedo retrievals to data from the Greenland Climate Network (GCN) weather stations and the floating ice station Tara for polar summer 2007. The AVHRR dataset consists of 2755 overpasses. The overpasses are matched to in situ observations spatially and temporally. The SAL algorithm presented here derives the surface broadband albedo from AVHRR channels 1 and 2 using an atmospheric correction, temporal sampling of an empirical Bidirectional Reflectance Distribution Function (BRDF), and a narrow-to-broadband conversion algorithm. The satellite product contains algorithms for snow, sea ice, vegetation, bare soil, and water albedo. At the Summit and DYE-2 stations on the Greenland ice sheet, instantaneous SAL RMSE is 0.073. The heterogeneous surface conditions at satellite pixel scale over the stations near the Greenland west coast increase RMSE to >0.12. Over Tara, the instantaneous SAL RMSE is 0.069. The BRDF sampling approach reduces RMSE over the ice sheet to 0.053, and to 0.045 over Tara. Taking into account various sources of uncertainty for both satellite retrievals and in situ observations, we conclude that SAL agrees with in situ observations within their limits of accuracy and spatial representativeness. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents 3D seismic data to enhance our understanding of the seismic stratigraphy and buildup developments of the Finnmark Platform. We focus on carbonate buildup distributions and platform geometry in space and upper Palaeozoic time. Multi-attribute analysis, neural network techniques and the use of inverted impedance data reveal seismic anomalies that can be linked with significant geological geometries such as buildups, subtle prograding clinoforms, karstified surfaces or platform breaks. The seismic expressions show a platform development mainly driven by climatic changes and differential subsidence. Seismic data indicate the first progradation of a low angle warm-water carbonate ramp during Mid Carboniferous times. A gradual change from a low angle (mixed) carbonate ramp to a more restricted carbonate shelf with a marked break and slope occurs during Upper Carboniferous/Lower Permian (Gipsdalen Group). Large buildups on the platform are identified both as individual mounds and unique continuous complexes (e.g. network of polygonal ridges as well as a 30-km long barrier complex). Multi-attribute analysis reveals a distinct karst event on top of the Gipsdalen Group. Climatic cooling during the Lower Permian (Bjarmeland Group) resulted in an even more restricted platform as seen in the seismic data with developments of 200-m high bryozoan mounds in deeper waters of the platform slope. Further cooling during Mid Permian (Tempelfjorden Group) resulted in a major chert event with development of a series of spiculitic chert mounds. [Copyright &y& Elsevier]

Marine birds are sensitive indicators of the condition of marine ecosystems in the Arctic, partly because they feed at the top of the arctic food chain. The Northern Ecosystem Initiative (NEI) recently supported four separate studies that investigated aspects of Arctic marine bird science which simultaneously addressed goals of the NEI to better understand northern ecosystems and their response to environmental stressors. The projects used both scientific and traditional knowledge to examine the relationship between sea-ice, contaminants, and the ecology of marine birds, and to transfer environmental knowledge to students. Results from these investigations confirm that changes are occurring in Arctic environments, and that these are captured through marine bird research. Collectively these studies provided new data that supported NEI objectives of monitoring the health of the Arctic ecosystem, and contributed to Canada's international obligations for Arctic science. [ABSTRACT FROM AUTHOR]

Abstract: Rapidly-flowing sectors of an ice sheet (ice streams) can play an important role in abrupt climate change through the delivery of icebergs and meltwater and the subsequent disruption of ocean thermohaline circulation (e.g., the North Atlantic''s Heinrich events). Recently, several cores have been raised from the Arctic Ocean which document the existence of massive ice export events during the Late Pleistocene and whose provenance has been linked to source regions in the Canadian Arctic Archipelago. In this paper, satellite imagery is used to map glacial geomorphology in the vicinity of Victoria Island, Banks Island and Prince of Wales Island (Canadian Arctic) in order to reconstruct ice flow patterns in the highly complex glacial landscape. A total of 88 discrete flow-sets are mapped and of these, 13 exhibit the characteristic geomorphology of palaeo-ice streams (i.e., parallel patterns of large, highly elongated mega-scale glacial lineations forming a convergent flow pattern with abrupt lateral margins). Previous studies by other workers and cross-cutting relationships indicate that the majority of these ice streams are relatively young and operated during or immediately prior to deglaciation. Our new mapping, however, documents a large (>700 km long; 110 km wide) and relatively old ice stream imprint centred in M''Clintock Channel and converging into Viscount Melville Sound. A trough mouth fan located on the continental shelf suggests that it extended along M''Clure Strait and was grounded at the shelf edge. The location of the M''Clure Strait Ice Stream exactly matches the source area of 4 (possibly 5) major ice export events recorded in core PS1230 raised from Fram Strait, the major ice exit for the Arctic Ocean. These ice export events occur at ∼12.9, ∼15.6, ∼22 and 29.8 ka (14C yr BP) and we argue that they record vigorous episodes of activity of the M''Clure Strait Ice Stream. The timing of these events is remarkably similar to the North Atlantic''s Heinrich events and we take this as evidence that the M''Clure Strait Ice Stream was also activated around the same time. This may hold important implications for the cause of the North Atlantic''s Heinrich events and hints at the possibility of a pan-ice sheet response. [Copyright &y& Elsevier]

We present a 500‐year history of naturally felled driftwood incursion to northern Svalbard, directly reflecting regional sea ice conditions and Arctic Ocean circulation. Provenance and age determinations by dendrochronology and wood anatomy provide insights into Arctic Ocean currents and climatic conditions at a fine spatial resolution, as crossdating with reference chronologies from the circum‐Arctic boreal forests enables determination of the watershed the driftwood originated from. Sample crossdating may result in a wide range of matches across the pan‐boreal region, which may be biased toward regions covered by the reference chronologies. Our study considers alternate approaches to selecting probable origin sites, by weighting scores via reference chronology span and visualizing results through spatiotemporal density plots, as opposed to more basic ranking systems. As our samples come from naturally felled trees (not logged or both), the relative proportions of different provenances are used to infer past ocean current dominance. Our record indicates centennial‐to decadal‐scale shifts in source regions for driftwood incursion to Svalbard, aligning with Late Holocene high variability and high frequency shifts in the Transpolar Drift and Beaufort Gyre strengths and associated fluctuating climate conditions. Driftwood occurrence and provenance also track the northward ice formation shift in peripheral Arctic seas in the past century. A distinct decrease in driftwood incursion during the last 30 years matches the observed decline in pan‐Arctic sea ice extent in recent decades. Our new approach successfully employs driftwood as a proxy for Arctic Ocean surface circulation and sea ice dynamics. Plain Language Summary: We present a 500‐year history of driftwood arriving to the shorelines of northern Svalbard. Driftwood in the Arctic results from dying trees entering the large rivers that drain the circum‐Arctic land masses, which upon flowing into the Arctic Ocean can become locked up in forming sea ice. This enables the wood to travel across the Arctic Ocean without sinking, making it an invaluable proxy for sea ice extent by recording variations in Arctic Ocean surface currents (and therefore sea ice drift) and ice cover. With comparison of tree ring width (TRW) measurements of these driftwood samples to TRW series from trees throughout the boreal forests, we can determine the region each sample came from. We can thus approximate its likely trajectory across the Arctic Ocean. Arctic sea ice is rapidly declining in extent and thickness, with impacts on local and global climatic and ecological conditions. Knowledge of past changes is needed to place this modern trend within a broader context to aid future predictions for Arctic sea ice. Our record matches the observational record of Arctic Ocean surface circulation patterns and climate conditions, supporting the use of driftwood as a proxy for Arctic Ocean surface current and sea ice dynamics. Key Points: We present a novel approach to utilizing naturally felled driftwood as a proxy for Arctic Ocean surface circulation and sea ice dynamicsA 500‐year record of driftwood incursion to Svalbard reflects centennial to decadal variability in surface circulation and sea ice extentA distinct decrease in driftwood from all provenances in the last 30 years matches the observed decline in pan‐Arctic sea ice extent [ABSTRACT FROM AUTHOR]

The Arctic is of great significance to global weather and climate systems. However, its atmospheric conditions have yet to be fully understood, partly because of the lack of intensive observations. Here we reported on the characteristics of lower troposphere over the Arctic Ocean using high‐resolution radiosonde data collected during the 5th Chinese National Arctic Research Expedition from July to September 2014. Statistical analyses showed that temperature inversion (TI) occurred most frequently below 700 m, without apparent temporal variability between morning and noon. In contrast, the occurrence frequency of morning surface‐based inversion (SBI) was always higher than at noon in the whole boundary layer, whereas the elevated inversion (EI) frequency seemed much lower in the morning compared with at noon. More frequent deeper clouds tended to occur in the morning than at noon, which led to more frequent EI than SBI. SBI was found to dominate the clear‐sky condition, whereas EI was generally observed under cloudy conditions. Regarding the seasonal variation, deep TI and clouds dominated during the first intensive observational period (IOP‐1; July 21–31) because of warm advection in combination with heating effects induced by long‐range transported black carbon (BC). During IOP‐2 (August 1–18), synoptic scale subsidence prevailed, with frequent EI and SBI partly caused by BC accumulation over the Arctic Ocean. In comparison, more clouds and less TI occurred during IOP‐3 (August 27–September 11) largely due to the outbreaking polar vortex. These observations contribute to a better understanding of vertical temperature and cloud structures under global warming. Plain Language Summary: The Arctic, one of climate sensitive regions in the world, is of great importance to the global climate systems. Nevertheless, the temperature and cloud profiles are key indicators of ocean‐atmosphere interaction and remain poorly understood. In this study, the main characteristics of temperature and clouds in the lower troposphere were investigated over the Arctic Ocean using high‐resolution radiosonde data collected during the 5th Chinese National Arctic Research Expedition from July to September 2014. The clouds led to more frequent elevated inversion (EI) than surface‐based inversion (SBI), while SBI dominated under clear‐sky conditions. Significant diurnal variation exhibited of SBI and EI, with much high SBI frequency in the morning than at noon likely due to the radiative cooling. Besides, polar vortex, advection, and black carbon took turns to dominate the frequency of TI and cloud in the Arctic, depending on the time period under investigation. The findings obtained here have important implications for improving our understanding of the ocean‐atmosphere coupled system over the Arctic Ocean. Key Points: The clouds led to more frequent elevated inversion than surface‐based inversion, while SBI dominated under clear‐sky conditionsSBI frequency shows much stronger dependence on environmental variables than EI in the Arctic regionPolar vortex, advection, and black carbon took turns to dominate the frequency of TI and cloud in the Arctic, depending on the time studied [ABSTRACT FROM AUTHOR]

Hydrographic data collected from research cruises, bottom‐anchored moorings, drifting Ice‐Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997–2018) accompanied by sea ice melt, a wind‐forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice‐Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year‐to‐year variability, or the more subtle interannual variations. The Beaufort Gyre centered in the Canada Basin of the Arctic Ocean is the major reservoir of fresh water in the Arctic. The primary focus of this study is on quantifying variability and trends in liquid (water) and solid (sea ice) freshwater content in this region. The Beaufort Gyre Exploration Program was initiated in 2003 to synthesize results of historical data analysis, design and conduct long‐term observations, and to provide information for numerical modeling under the umbrella of the FAMOS (Forum for Arctic Observing and Modeling Synthesis) project. The data collected from research cruises, moorings, Ice‐Tethered Profiler observations, and satellite altimetry document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018, a 40% growth relative to the climatology of the 1970s. This fresh water volume is comparable to the fresh water volume released to the sub‐arctic seas during the Great Salinity Anomaly episode of the 1970s. Thus, since the 2000s, the stage has been set for another possible release of fresh water to lower latitudes with accompanying climate impacts, including changes to sea ice conditions, ocean circulation, and ecosystems of the Sub‐Arctic similar to the influence of the Great Salinity Anomaly observed in the 1970s. Key Points: Beaufort Gyre freshwater content time series (2003–2018) from different data sets are updated, compared, and analyzedQualitative and quantitative estimates of factors and mechanisms driving freshwater content changes are providedIn 2003–2018, the major sources of accumulated fresh water were sea ice melt, Mackenzie River runoff, and Bering Strait transport [ABSTRACT FROM AUTHOR]

Since the 1980–1990s, international research efforts have augmented our knowledge of the physical and chemical properties of the Arctic Ocean water masses, and recent studies have documented changes. Understanding the processes responsible for these changes is necessary to be able to forecast the local and global consequences of these property evolutions on climate. The present work investigates the distributions of geochemical tracers of particle fluxes and circulation in the Amerasian Basin and their temporal evolution over the last three decades (from stations visited between 1983 and 2015). Profiles of 230‐thorium (230Th) and 231‐protactinium (231Pa) concentrations and neodymium isotopes (expressed as εNd) measured in the Amerasian Basin prior to 2000 are compared to a new, post‐2000s data set. The comparison shows a large scale decrease in dissolved 230Th and 231Pa concentrations, suggesting intensification of scavenging by particle flux, especially in coastal areas. Higher productivity and sediment resuspension from the shelves appear responsible for the concentration decrease along the margins. In the basin interior, increased lateral exchanges with the boundary circulation also contribute to the decrease in concentration. This study illustrates how dissolved 230Th and 231Pa, with εNd support, can provide unique insights not only into changes in particle flux but also into the evolution of ocean circulation and mixing. Plain Language Summary: The Arctic Ocean is one of the oceanic regions most affected by climate change. The increasing summer retreat of sea ice allows greater atmosphere‐ocean exchanges and light penetration, while land‐ocean exchanges are expected to increase, due to enhanced continental erosion (notably through permafrost thawing and increased river flow). These changes are driven by climate and in turn impact the climate. This study aims at assessing possible shifts in oceanic circulation and particle fluxes resulting from these climate‐driven changes in the Amerasian Basin of the Arctic Ocean, during the last few decades. To achieve this goal, we measured geochemical tracers of circulation and particle fluxes in seawater samples collected in this area between 2005 and 2015, which we compared to published data from samples collected between 1983 and 2000. The primary geochemical tracers studied here are 230Th and 231Pa. These radioisotopes are uniformly produced in seawater, from uranium decay, and are strongly reactive with particles. Therefore, their oceanic distribution depends on particle fluxes and circulation. The evolution of their distribution in the Amerasian Basin over space and time documents enhancement of particle flux and lateral mixing in the Amerasian basin of the Arctic Ocean over the last three decades. Key Points: Concentration decreases of 230Thd and 231Pad suggest an enhancement of particulate scavenging since the 2000s in the Amerasian BasinParticulate scavenging results from higher productivity and sediment resuspension from the shelvesPost‐2000s changes in intermediate and deep layers suggest enhanced lateral mixing between the margins and central areas of the basins [ABSTRACT FROM AUTHOR]

Although scientists disagree about the rate at which Arctic ice is melting, climate change will greatly alter the northern latitudes in coming decades if greenhouse gas emissions are not curtailed. Many of the expected changes will be negative; already, permafrost is melting in Siberia, and apartments and factories are sinking into quagmires. The melting of Arctic ice, however, will also open sea-lanes to shipping and allow access to enormous oil and gas reserves beneath the Arctic Ocean. The prospect of increased Arctic commerce brings with it competition among countries and companies for control of the area’s riches, and international competition always carries the possibility of conflict. Three authors, all experts in national security and the Arctic, explore the military, diplomatic, environmental, and economic outlook for the Arctic in 2030: from Russia, Yury Morozov (2012); from Canada, Rob Huebert (2012); and from the United States, George Backus. [ABSTRACT FROM PUBLISHER]

The Arctic Ocean is experiencing profound environmental changes as the climate warms. Understanding how these changes will affect Arctic biological productivity is key for predicting future Arctic ecosystems and the global CO2 balance. Here we use in situ gas measurements to quantify rates of gross oxygen production (GOP, total photosynthesis) and net community production (NCP, net CO2 drawdown by the biological pump) in the mixed layer in summer or fall from 2011 to 2016 in the Beaufort Gyre. NCP and GOP show spatial and temporal variations with higher values linked with lower concentrations of sea ice and increased upper ocean stratification. Mean rates of GOP range from 8 ± 1 to 54 ± 9 mmol O2·m−2·d−1 with the highest mean rates occurring in summer of 2012. Mean rates of NCP ranged from 1.3 ± 0.2 to 2.9 ± 0.5 mmol O2·m−2·d−1. The mean ratio of NCP/GOP, a measure of how efficiently the ecosystem is recycling its nutrients, ranged from 0.04 to 0.17, similar to ratios observed at lower latitudes. Additionally, a large increase in total photosynthesis that occurred in 2012, a year of historically low sea ice coverage, persisted for many years. Taken together, these data provide one of the most complete characterizations of interannual variations of biological productivity in this climatically important region, can serve as a baseline for future changes in rates of production, and give an intriguing glimpse of how this region of the Arctic may respond to future lack of sea ice. Plain Language Summary: The Arctic Ocean is changing rapidly because of global climate change. Sea ice is declining, with the Arctic expected to be ice‐free in the summer by the middle of this century. The effect of these environmental changes on the marine carbon cycle is poorly known. In this study, rates of marine photosynthesis and net carbon dioxide drawdown in the summer or fall of 2011–2016 show that ice concentration was the largest environmental predictor of biological productivity, with smaller sea ice concentrations leading to increased rates of photosynthesis and thus likely to higher carbon dioxide drawdown. Additionally, a large increase in total photosynthesis that occurred in 2012, a year of historically low sea ice coverage, persisted for many years. An alternative hypothesis for the large increase in photosynthesis in 2012 is that the data in 2011 were collected before the onset of summer stratification (time when mixed layer depth gets very shallow), whereas data for all subsequent years were collected after this increase in stratification had occurred. Key Points: Sea ice concentration is the environmental factor that has the strongest correlation with net community production and photosynthesisRates of net community production and total photosynthesis were significantly positively correlated with N2, an index of stratificationOne interpretation suggests that as sea ice melts, the gyre will have large increases in photosynthesis but small ones in net CO2 drawdown [ABSTRACT FROM AUTHOR]

There is increasing interest in the magnitude of the flow of freshwater to the Arctic Ocean due to its impacts on the biogeophysical and socio‐economic systems in the north and its influence on global climate. This study examines freshwater flow based on a dataset of 72 rivers that either directly or indirectly contribute flow to the Arctic Ocean or reflect the hydrologic regime of areas contributing flow to the Arctic Ocean. Annual streamflow for the 72 rivers is categorized as to the nature and location of the contribution to the Arctic Ocean, and composite series of annual flows are determined for each category for the period 1975 to 2015. A trend analysis is then conducted for the annual discharge series assembled for each category. The results reveal a general increase in freshwater flow to the Arctic Ocean with this increase being more prominent from the Eurasian rivers than from the North American rivers. A comparison with trends obtained from an earlier study ending in 2000 indicates similar trend response from the Eurasian rivers, but dramatic differences from some of the North American rivers. A total annual discharge increase of 8.7 km3/y/y is found, with an annual discharge increase of 5.8 km3/y/y observed for the rivers directly flowing to the Arctic Ocean. The influence of annual or seasonal climate oscillation indices on annual discharge series is also assessed. Several river categories are found to have significant correlations with the Arctic Oscillation, the North Atlantic Oscillation, or the Pacific Decadal Oscillation. However, no significant association with climate indices is found for the river categories leading to the largest freshwater contribution to the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Abstract Atmospheric deposition is the main input of mercury (Hg) to the ocean, even in remote locations such as the Arctic. Furthermore, evasion of elemental Hg (Hg°) is the major sink for oceanic Hg. As a result, air-sea exchange is an important part of the oceanic Hg cycle. To examine the air-sea exchange of Hg in the Arctic Ocean we made high resolution measurements of Hg° in surface waters and Hg speciation in the atmosphere using continuous sampling systems during the 2015 U.S. Arctic GEOTRACES cruise from August 9 to October 12. Additionally, samples were obtained for measurement of total Hg and methylmercury (CH 3 Hg) in wet deposition and bulk aerosols as well as surface snow and sea ice. We used these measurements made in the water and the atmosphere to estimate fluxes of Hg° from the ocean to the atmosphere. Concentrations of dissolved Hg° (Hg° diss) were near saturation in ice-free waters (32 ± 30 fM) and resultant fluxes were low; however, Hg° was highly enriched under contiguous ice (101 ± 98 fM, up to 544 fM) suggesting the continual formation of Hg° in waters even when ice covered. Predicted evasion fluxes in these regions (these being potential rates for locations under ice) were as high as 492 pmol m−2 h−1. Atmospheric Hg° concentrations averaged 1.2 ± 0.1 ng m−3 with little variation over the course of the cruise even above waters with elevated Hg° diss , indicating that sea ice acts as a barrier to air-sea exchange. Measurements of Hg in precipitation and aerosols were lower than have been found in more coastal regions of the Arctic. We used these concentrations to estimate deposition of Hg and CH 3 Hg during the time of the cruise. Overall, wet deposition represented 88% of the CH 3 Hg flux and 38% of the Hg T flux. Our flux estimates confirm the importance of air-sea exchange in Hg cycling in the Arctic and suggest that evasion was greater than deposition, indicating a net loss of Hg from the Arctic during this period or the presence of other sources not measured during this study. Additionally, our results suggest that fluxes for offshore waters are lower than found in coastal regions of the Arctic. From these estimates, we predict how Hg concentrations may respond to future changes in ice cover and other potential impacts of climate change on Hg dynamics and food web bioaccumulation in this important ocean region. Highlights • Dissolved Hg° was supersaturated under ice but near saturation in open waters. • Sea ice acted as a barrier to air-sea exchange of Hg. • Atmospheric Hg° concentrations (averaging 1.2 ± 0.1 ng m−3) were relatively constant. • Hg in precipitation and aerosols lower over open ocean than in coastal locations. • Hg° fluxes were predicted for open and ice-covered waters. [ABSTRACT FROM AUTHOR]

The article focuses on the August 2004 expedition by an international team of researchers that extracted 400 meters of sediment core from the Arctic Sea floor. Past climate changes in the Arctic are revealed using the sedimentary record. The technological advances made possible by the expedition are discussed. A seafloor-drilling system is needed to make expeditions easier.