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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]

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]

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]

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]

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]

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]

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 northernmost limb of the Atlantic Meridional Overturning Circulation (AMOC), so relevant for understanding decadal climate variability, enters the Nordic Seas as the Norwegian Atlantic Current and continues on to recirculate in the Arctic Ocean. The strength of the Eastern Branch of the Norwegian Atlantic Current has been systematically monitored for over 15 years at the Svinøy section off southern Norway, whereas the strength of the Western Branch has not. We therefore used autonomous gliders to monitor and quantify the strength of this broader branch at the Svinøy section, located 500km downstream from the Iceland–Scotland Ridge, and at the Station Mike section 300km further downstream. The gliders' diving depth is 1000m, spanning the warm Atlantic Water. The current encompasses more than warm Atlantic Water; we find that the transport peaks in two distinct temperature ranges, one around 7.5–8°C (Atlantic Water, carrying 7Sv (1×106 m3/s)) and another around −0.5°C (Norwegian Sea Deep Water, carrying 12Sv). Contrary to earlier expectations, our results indicate that the Western Branch carries as much water of Atlantic origin (temperature>7.5°C) as the Eastern Branch. It should therefore be included in future monitoring plans for this region. [ABSTRACT FROM AUTHOR]