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Measurements of oceanographic characteristics, currents, and tides in the Fram Strait and the Greenland Sea are analyzed using historical measurement data. Measurements on moorings across the Fram Strait made it possible to estimate the speeds of the East Greenland and West Spitsbergen currents. It is shown that the speeds of these currents are low (within 10 cm/s) and the amplitudes of the speed of tidal currents are two or more times greater. Tidal currents are intensifying on the shelf of Greenland and Svalbard. Direct measurements are compared with the University of Oregon barotropic tide model. [ABSTRACT FROM AUTHOR]

Sea ice edges play an essential role in the Earth's climate and weather systems through active atmosphere‐ice‐ocean interactions. However, our understanding of the observed positions of sea ice edges remains limited. The present study investigated, on seasonal and longer timescales from 1979 to 2023, the variability in sea ice edge positions in the Barents and Greenland Seas. We objectively derived the positions of sea ice edges based on satellite‐derived sea ice concentration gridded on a 25‐km resolution. In the Barents Sea, warm, narrow currents flow eastward along the northern and southern rims of the Central Bank. Until the mid‐2000s, sea ice edges fluctuated between these currents interannually during December–June, depending on the surface wind direction. However, after the mid‐2000s, the sea ice edges were mostly positioned near the northern current or farther to the north. Furthermore, sea ice edges during October–March were identified frequently near the warm current flowing along the continental slope in the northern Barents Sea after the mid‐2000s. In the Greenland Sea, sea ice edges were typically positioned near the East Greenland Current (EGC) throughout the year until 2006. However, sea ice edges in summer were located far to the west of the EGC after 2006. These observations suggest that the geographical relationship between sea ice edges and ocean currents has changed due to global warming. Plain Language Summary: Sea ice edges in the Arctic play an important role in the Earth's climate system. They can strengthen atmospheric cyclones and vertical motion in the atmosphere and the ocean in the Arctic by inducing intense heat and moisture releases from the ocean to the atmosphere. Furthermore, they could exert distinct impacts on global‐scale atmosphere and ocean circulations. Therefore, a deeper understanding of the geographical positions of sea ice edges is essential for elucidating the climate system. This study investigated the sea ice edge positions in the Barents and Greenland Seas using satellite observations from 1979 to 2023. Sea ice edges rapidly advance southward during winter. Until the mid‐2000s, sea ice edges were frequently identified along warm ocean currents in the Barents and Greenland Seas because warm currents obstruct further sea ice edge advances. However, sea ice edges have shifted far to the north of warm ocean currents after the mid‐2000s in association with the recent shrinking in sea ice extent due to global warming. The change in sea ice edge positions might have affected the atmosphere and ocean circulations globally, which should be addressed in future studies. Key Points: In the central Barents Sea, sea ice edge positions fluctuated in winter until the mid‐2000s but have lately fixed along a warm currentSince the mid‐2000s, sea ice edges have been frequently identified along the continental slope in the northern Barents Sea in winterUntil 2006, sea ice edges in the Greenland Sea were located at the East Greenland Current, but they shifted far west after 2006 in summer [ABSTRACT FROM AUTHOR]

The COVID-19 lockdown had a significant impact on human activities, reducing anthropogenic heat and CO2 emissions. To effectively assess the impact of the lockdown on the thermal environment, we used the sliding paired t-test, which we improved from the traditional sliding t-test by introducing the paired t-test for sliding statistical tests, to test the abrupt change in the thermal environment. Furthermore, an additive decomposition model and wavelet analysis method were used to analyze the characteristics of trend and irregular change, coherence, and phase difference of the time series data with respect to the thermal environment. We chose the Greenland Sea and the Norwegian Sea, regions highly sensitive to changes in climate and ocean circulation, as case studies and used remote sensing data of the sea surface temperature (SST) and the atmospheric CO2 concentration data obtained from the Goddard Earth Sciences Data and Information Services Center from January 2015 to December 2021 for the analysis. The results show that although the annual spatial mean SST in 2020 is lower than the mean of all 7 years in most areas of the two seas, there is no evidence of a significant mutation in the decrease in the SST during the lockdown in 2020 compared with the temperatures before, according to the sliding paired t-test. The analysis of the irregular components of the monthly mean SST decomposed by an additive decomposition model also does not show the anomalously low SST during the lockdown in 2020. In addition, the lockdown had almost no impact on the increasing trend of CO2 concentration. The wavelet analysis also shows that there is no obvious anomaly in coherence or phase difference between the periodic variation of the SST and the CO2 concentrations in 2020 compared with other years. These results suggest that the direct effect of the COVID-19 lockdown on the thermal environment of the study area could be negligible. [ABSTRACT FROM AUTHOR]

Seasonal and interannual changes in the Greenland Sea ice age composition during winter months for seven standard age categories are analyzed. To estimate the amount of the ice of different age categories, the digital archive of the region's ice charts for the period 1997–2022 produced by the Arctic and Antarctic Research Institute is used. Statistical insignificance of linear trends has been revealed for the main age categories of the Greenland Sea ice. A comparison of the obtained estimates of the variability in the amount of the ice of different age categories and earlier studies shows that the quantitative changes in the Greenland Sea ice age composition started before 1997. The data on the ice age composition over a 25-year observation period alone are insufficient to draw an unambiguous conclusion about a decrease in the Greenland Sea ice thickness. [ABSTRACT FROM AUTHOR]

Vesteris Seamount is a large Quaternary intraplate submarine volcano in the SW Greenland Sea, about 1,000 km NE of Iceland and 300 km NW of the Mohn's spreading ridge, whose mode of formation remains unsolved. We present geochemical data for new samples dredged from the Vesteris edifice, including major, trace elements and Sr‐Nd‐Pb‐Hf isotopes. The isotopic characteristics of the alkaline lavas, covering the basanite/tephrite to benmoreite range, indicate the involvement of depleted and enriched mantle components. The source is dominated by the depleted mantle (85%–90%) and a deep enriched component possibly supplied by the Iceland Plume (IP) (10%–15%). Additional source enrichment was due to recycled crust and sub‐continental lithospheric mantle, as suggested by Hf isotopes (0.283147 ± 0.000005) measured for the first time in Vesteris lavas and by a decoupling in Pb isotopes evidenced by relatively low‐radiogenic 207Pb/204Pb (15.510) and high‐radiogenic 208Pb/204Pb (38.554) with respect to the Northern Hemisphere Reference Line. We interpret the geochemical results using existing knowledge about the regional lithospheric and upper mantle structure. Our findings suggest that a deep (ca. 420–320 km) mantle anomaly, with seismological characteristics of the Iceland mantle plume, extends from East Greenland to the north of Jan Mayen Fracture Zone. The regional lithospheric thinning toward the Greenland Basin enabled the melting events that produced the Vesteris seamount. This lateral NNE‐directed flow lobe of the Iceland plume may have carved and transferred enriched components from the continental lithospheric margin of Greenland north of Scoresby Sund toward the Vesteris source. Plain Language Summary: This study investigates the formation of Vesteris Seamount, the largest submarine volcano in the Greenland Sea, situated north of Iceland and the Jan Mayen Fracture Zone and east of the Greenland continental margin. Given the isolated position of Vesteris, it is challenging to define its formation mechanisms and the mantle source. This study presents geochemical data by analyzing samples dredged from Vesteris' flanks. A deep mantle component, similar to the Iceland plume, seems to contribute to the mantle source of Vesteris magmas and the regional depleted asthenosphere. However, our results also suggest a contribution of an enriched component. This could be the sub‐continental mantle lithosphere (SCLM) and a crustal component. These components could have been transported from the Northeastern Greenland Margin, North of Scoresby Sund, along with the mantle flow. Subsurface seismic tomography images indicate an NNE‐directed flow lobe from the mantle plume under Iceland. We suggest that this setting played an important role in the seamount formation and explain the isotope signatures of SCLM‐like and crustal components by deep mantle carving of the western Greenland margin. Key Points: New volcanic rock samples are dredged from Vesteris Seamount in the SW Greenland SeaSample analysis shows geochemical evidence of deep mantle component and continental crust remobilizationMelting underneath Vesteris was enhanced by steep lithospheric thickness change that allowed channeling of the Iceland plume branch [ABSTRACT FROM AUTHOR]

The COVID-19 lockdown had a significant impact on human activities, reducing anthropogenic heat and CO2 emissions. To effectively assess the impact of the lockdown on the thermal environment, we used the sliding paired t-test, which we improved from the traditional sliding t-test by introducing the paired t-test for sliding statistical tests, to test the abrupt change in the thermal environment. Furthermore, an additive decomposition model and wavelet analysis method were used to analyze the characteristics of trend and irregular change, coherence, and phase difference of the time series data with respect to the thermal environment. We chose the Greenland Sea and the Norwegian Sea, regions highly sensitive to changes in climate and ocean circulation, as case studies and used remote sensing data of the sea surface temperature (SST) and the atmospheric CO2 concentration data obtained from the Goddard Earth Sciences Data and Information Services Center from January 2015 to December 2021 for the analysis. The results show that although the annual spatial mean SST in 2020 is lower than the mean of all 7 years in most areas of the two seas, there is no evidence of a significant mutation in the decrease in the SST during the lockdown in 2020 compared with the temperatures before, according to the sliding paired t-test. The analysis of the irregular components of the monthly mean SST decomposed by an additive decomposition model also does not show the anomalously low SST during the lockdown in 2020. In addition, the lockdown had almost no impact on the increasing trend of CO2 concentration. The wavelet analysis also shows that there is no obvious anomaly in coherence or phase difference between the periodic variation of the SST and the CO2 concentrations in 2020 compared with other years. These results suggest that the direct effect of the COVID-19 lockdown on the thermal environment of the study area could be negligible.

The Greenland Sea is a key region for open ocean convection and ventilation, which exhibit a large variability with periods of strong convection and shutdowns. After a long period of weak winter convection (from the 1970s to the early 1990s), a recovery has been reported, beginning in the 1990s and intensifying in the early 2000s until 2013. Using ISAS, an optimal interpolation product based on Argo observations, we document a recent significant weakening of deep convection between 2014 and 2020, accompanied by a continuous warming of the mixed layer but also a freshening after 2014. These hydrographic changes likely increase the ocean stratification and precondition the shutdown of winter convection. We suggest that these property changes result from a shift of the large scale atmospheric circulation, affecting the source of Atlantic Water to the Nordic seas, causing a freshening of about −0.1 g kg−1 that spreads into the Greenland Sea. Plain Language Summary: The Greenland Sea is a key region for the climate system. There, during winter, the ocean loses heat to the atmosphere in a process called "deep convection," that results in the formation of dense water masses that ventilate and fill the deeper layers of the ocean. The Greenland Sea exhibits a high variability in the intensity of winter deep convection, but the scientific community is still debating on which processes trigger or stop convection. After a recovery period of convection, mainly in the beginning of the 21st century, convection has stopped again after 2014 and at least until 2020. Here, we suggest that this new shutdown is mainly caused by changes in the ocean upper layer temperature and salinity that increase the upper ocean buoyancy, making it more difficult to trigger deep convection during winter. We further propose that the main mechanism driving the ocean properties changes is a shift of the large scale atmospheric circulation, which affects the amount and properties of Atlantic Water transported to the Greenland Sea. Key Points: After a period of intense deep convection since 2002, convection in the Greenland Sea has weakened from 2014 to 2020The upper salinity and temperature in the months prior of convection are driving the deep convection variabilityThe upper salinity changes are resulting from changes in large scale pattern of advection [ABSTRACT FROM AUTHOR]

The seasonally ice-covered marine region of the European Arctic has experienced warming and sea ice loss in the last two decades. During expeditions in August 2020 and 2021, new data on size-fractioned primary production (PP), chlorophyll a concentration, phytoplankton biomass and composition and carbon fixation rates in the dark were obtained in the marginal ice zone (MIZ) of the Barents Sea, Nansen Basin and Greenland Sea to better understand the response of Arctic ecosystems to ongoing climate changes. Four different situations were observed in the study region: (i) a bloom of the large-cell diatom Podosira glacialis, whose biomass was trapped in a strong halocline at the edge of a dense ice cover; (ii) a bloom of the chain-like colonies of Thalassiosira diatoms on the shelf in mixed waters in fields of shallow ice that could be supported by "fresh" elements in the polynya condition, as well as by terrestrial run-off and drifting ices; at the late stage, this bloom was accompanied by intensive growth of Phaeocystis pouchetti; (iii) dominance of small-cell phytoplankton under weakened stratification and the significant influence of the Atlantic water, depleted of microelements and silicates; (iv) dominance of dinoflagellates of eutrophic water in the contact zone between the water masses of Arctic origin and Atlantic origin in clear water under conditions of increased light intensity. The >10 µm phytoplankton cell size group increased its relative contribution to PP as a response to stratification, light and nutrient load associated with sea ice conditions. Small phytoplankton with sizes < 2 µm formed the basis of total PP in the MIZ regardless of the state of the sea ice. [ABSTRACT FROM AUTHOR]

Pleistocene basanitic rocks of Vesteris Seamount in the Greenland Sea had been found to exhibit an endolithic habitat largely consisting of marine fungi that dwell within abundant vesicles, therefore representing cryptoendoliths. For the first time, we demonstrate that 3D X‐ray microscopy can unravel how microorganisms access and migrate through vesicular rock. The fossil assemblages occur within a set of vesicles connected by microcracks. Such microcracks, which are ubiquitous features in submarine volcanic rocks, enable the dispersal of marine microorganisms in the rock. This study suggests that this pathway for the colonization of marine volcanic rocks forms in consequence of early tensional stress due to variable rates of cooling of the lava flow. Subsequently, the interconnected vesicles get populated by rock‐dwelling microorganisms. This cryptoendolithic habitat exists at least since the Paleoproterozoic. [ABSTRACT FROM AUTHOR]

Arctic food webs are being impacted by borealisation and environmental change. To quantify the impact of these multiple forcings, it is crucial to accurately determine the temporal change in key ecosystem metrics, such as trophic position of top predators. Here, we measured stable nitrogen isotopes (δ15N) in amino acids in harp seal teeth from across the North Atlantic spanning a period of 60 years to robustly assess multi‐decadal trends in harp seal trophic position, accounting for changes in δ15N at the base of the food web. We reveal long‐term variations in trophic position of harp seals which are likely to reflect fluctuations in prey availability, specifically fish‐ or invertebrate‐dominated diets. We show that the temporal trends in harp seal trophic position differ between the Northwest Atlantic, Greenland Sea and Barents Sea, suggesting divergent changes in each local ecosystem. Our results provide invaluable data for population dynamic and ecotoxicology studies. [ABSTRACT FROM AUTHOR]

Abstract Seabed sediment maps underpin a variety of marine research endeavours. Seabed mapping data are available for many regions, but these usually provide discrete classifications which obscure underlying continuous properties of the sediments. Other areas are poorly surveyed, e.g., polar regions which are inaccessible due to ice cover. Here, we focus on the inaccessible North East Greenland shelf for which there are almost no seabed sediment data. We trained a random forest model to predict sediment classes from an existing map of the well‐surveyed neighbouring Barents Sea, using data on bathymetry, currents and waves. We then used our model to predict the unknown sediment distributions off East Greenland. In the process, we generated some new spatial data on previously un‐mapped properties of the Barents Sea, such as mean grain size, organic carbon and nitrogen content, porosity and permeability. The maps of both regions are available to support future research activities in the Arctic, e.g., the parameterization of benthic biogeochemistry in ecosystem models, or mapping species distributions.

Abstract The Greenland Sea is a key region for open ocean convection and ventilation, which exhibit a large variability with periods of strong convection and shutdowns. After a long period of weak winter convection (from the 1970s to the early 1990s), a recovery has been reported, beginning in the 1990s and intensifying in the early 2000s until 2013. Using ISAS, an optimal interpolation product based on Argo observations, we document a recent significant weakening of deep convection between 2014 and 2020, accompanied by a continuous warming of the mixed layer but also a freshening after 2014. These hydrographic changes likely increase the ocean stratification and precondition the shutdown of winter convection. We suggest that these property changes result from a shift of the large scale atmospheric circulation, affecting the source of Atlantic Water to the Nordic seas, causing a freshening of about −0.1 g kg−1 that spreads into the Greenland Sea.

We investigated wintertime convection evolution in recent years over the Greenland Sea. This area is a major location regarding dense water production and supply of the lower limb of the Atlantic Meridional Overturning Circulation, a key component of the global climate. Previous studies mentioned an increase in Greenland Sea wintertime convection intensity during the 2000s in comparison with the previous decade till 2015/2016. Here, we further document the ongoing oceanic changes within the Greenland Sea through the Mercator Ocean Physical System, an operational ocean model with data‐assimilation. The model has shown a large variability, a later start and a decline of convection in the Greenland Sea in recent years. In particular, the depth of the annual maximum mixed layer diminished by 52% between 2008–2014 and 2015–2020, from 1,168 to 559 m, over the convective area. This decline of the convection depth is corroborated with Argo float observations. Within the Greenland Sea, hydrographic changes especially the increasing temperature are associated with isopycnal deepening and stratification strengthening. The stratification is building up at a larger rate in the Boreas Basin compared to the Greenland Basin. The changes of the Greenland Sea hydrography in the model are in part related to Atlantic Water spreading over the Boreas Basin and the eastern part of the Greenland Basin. The model also indicates a decrease in the intensity of the gyre in accordance with the isopycnal deepening while local surface winds and fluxes do not exhibit significant trends nor significant interannual variations. Plain Language Summary: Surface warm and salty waters are losing heat as they flow poleward. Once they reach the subpolar Atlantic Ocean, they eventually sink to depth as they are getting denser. This vertical motion is called convection. This is an important process as it contributes to feeding the lower limb of the Atlantic Meridional Overturning Circulation, a key regulator of the global climate. In this study, we investigated wintertime convection evolution in recent years through an ocean model combined with observational data. We focused on the Greenland Sea, a main place regarding convection. The main result is that convection has weakened (in extent and intensity) in recent years. Convection is shallower, covers a smaller area and begins later in the winter. A contributing factor appears to be the rise in oceanic temperature at this location especially near the surface. Therefore it is crucial to keep monitoring this region as this rise in temperature is expected to continue in the future. Key Points: Mercator Ocean System well reproduced hydrographic properties and mixed layer depth evolution over the Greenland Sea from 2008 to 2020Maximum mixed layer depths in the Greenland Sea display a strong decline from 2015 onward in the model and in the observationsModel convection decrease is associated with stratification changes, Atlantic Water spreading and Greenland Sea Gyre weakening [ABSTRACT FROM AUTHOR]

Seabed sediment maps underpin a variety of marine research endeavours. Seabed mapping data are available for many regions, but these usually provide discrete classifications which obscure underlying continuous properties of the sediments. Other areas are poorly surveyed, e.g., polar regions which are inaccessible due to ice cover. Here, we focus on the inaccessible North East Greenland shelf for which there are almost no seabed sediment data. We trained a random forest model to predict sediment classes from an existing map of the well‐surveyed neighbouring Barents Sea, using data on bathymetry, currents and waves. We then used our model to predict the unknown sediment distributions off East Greenland. In the process, we generated some new spatial data on previously un‐mapped properties of the Barents Sea, such as mean grain size, organic carbon and nitrogen content, porosity and permeability. The maps of both regions are available to support future research activities in the Arctic, e.g., the parameterization of benthic biogeochemistry in ecosystem models, or mapping species distributions. [ABSTRACT FROM AUTHOR]

Here we investigate properties of ocean eddies in the key Arctic region of the northern Greenland Sea and the Fram Strait using visible and infrared Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua data acquired from April to September in 2007 and 2018–2020. We infer eddy properties using visual identification and automated processing of their signatures in sea surface temperature (SST) and chlorophyll-a (chl-a) maps, and their gradients. Altogether, 450 (721) eddies were identified in SST (chl-a) data. Their radii span from 2 to 40 km (mean value 12 km). Most eddies are elliptical with a mean aspect ratio (eccentricity) of their axes equal 0.77 (0.64). Cyclones are smaller than anticyclones and prevail in both data sources. Cyclones tend to be more prevalent over shallow shelves, and anticyclones over deep water regions. Peak eddy activity is registered in June, while chl-a data also possess a second peak in April. In SST, the highest eddy probability is found along the East Greenland Current in the Nordbukta region at 76–78°N and along the West Spitsbergen Current at 78–80°N. In chl-a, most of them are observed in the central Fram Strait. The overall number of eddies with a positive chl-a anomaly, dominated by cyclones, is larger (62%) than that with a negative one (~38%). The number of eddies with positive and negative SST anomalies is nearly equal. Eddy translation velocities are 0.9–9.6 km/day (mean value 4.2 km/day). Despite frequent cloud and ice cover, MODIS data is a rich source of information on eddy generation hot-spots, their spatial properties, dynamics and associated SST and chl-a anomalies in the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Arctic sea ice outflow to the Atlantic Ocean is essential to Arctic sea ice mass loss and the hydrographical and ecological environments in the Barents and Greenland Seas (BGS). In the context of the extremely positive Arctic Oscillation (AO) in January-March 2020, the impacts and feedback mechanisms on a seasonal scale of anomalies in Arctic sea ice outflow on winter-spring sea ice and other marine environmental conditions in the subsequent months until early summer in the BGS were investigated. The results reveal that the total sea ice area flux (SIAF) through the Fram Strait, the Svalbard-Franz Josef Land, and the Franz Josef Land-Novaya Zemlya passageways in January-March and June 2020 were higher than the 1988-2020 climatology, mainly through the Fram Strait (77.6 %). The interannual variability of this total SIAF was dominated by changes in ice motion speed (R = +0.86, P < 0.001). The relatively high ice speed along the Transpolar Drift in January-June 2020 was related to the positive phases of winter (JFM) AO and the winter-spring air pressure gradient across the western and eastern Arctic Ocean. The abnormally high Arctic sea ice outflow led to an increased sea ice area and thickness in the BGS, which has been observed since March 2020, especially in May-June. In this region, the April sea ice area was significantly negatively correlated with synchronous sea surface temperature (SST) as well as the lagging SST of 1-3 months. High sea ice area in spring (AMJ) 2020 also inhibited phytoplankton bloom, with an extremely low Chlorophyll-a concentration observed over the BGS in April. Therefore, this study suggests that winter-spring Arctic sea ice outflow can be considered as a predictor of changes in sea ice and other marine environmental conditions in the BGS in the subsequent months, at least until early summer. The results increase our understanding of the physical connection between the central Arctic Ocean and the peripheral seas. [ABSTRACT FROM AUTHOR]

Primary production (PP) and the chlorophyll-a concentration (chl-a) in the European Arctic in the summer of 2020–2021, where continued climatic warming and increased “Atlantification” accelerate the sea ice losses, are discussed. The maximum integrated PP and the total chl-a content were observed in the marginal ice zone (MIZ) of the Barents Sea under weakened stratification of the water column and reached 1109 mgC m–2 day–1 and 118 mg m–2. Near the ice edge in the Nansen Basin, the main part of PP formed in the upper mixed layer and did not exceed 469 mgC m–2 day–1; the chl-a content reached 56 mg m–2. The early and late stages of phytoplankton bloom in the MIZ were characterized by the leading role of picophytoplankton in carbon fixation. Large centric diatoms, microphytoplankton, were recorded to dominate in the MIZ at the stage of peak bloom in 2020 under the dense ice cover of the Nansen Basin. A similar phenomenon was observed earlier only in the Arctic shelf seas and was not recorded in the high-latitude basins of the Arctic Ocean. With the sparse ice cover of the Nansen Basin in 2021, the main primary producers were pico- and nanophytoplankton. The low variability of assimilation numbers (1.7 ± 0.3 mgC mg chl-a–1 h–1) at all bloom stages indicates indirectly the acclimatization of different species of phytoplankton to the environmental changes. The ecological flexibility of the primary production link of the MIZ ecosystems in the studied seas of the European Arctic during the period of climate changes is confirmed. [ABSTRACT FROM AUTHOR]

Biogenetic sulfide dimethylsulfide (DMS) plays a major role on the global climate, especially in Arctic Ocean. Accurate simulate DMS concentration is an important task. Here we introduced both biogeochemical depth-averaged model G93 and its extension model-one dimensional DMS model. Both surface concentrations, vertical profiles of chlorophyll (CHL) and DMS are simulated using the two models within southern Greenland Sea (0°E–10°E, 70°N–75°N) during year 2012. As the input data for the models simulations, the spatial monthly mean of methodology forcings including sea surface temperature (SST), wind speed (WIND), cloud cover (CLD), sea ice concentration (ICE) and mixed layer depth (MLD) are calculated. Satellite 8-day time series of chlorophyll-a (CHL) are used as observation data for CHL related parameter calibrations. Simó's imperial formula is used as the monthly DMS observation data. The Genetic Algorithm technique is used for the parameter calibrations. The simulation results show that the most DMS related surface concentrations exhibit the normal distributions with peak during May. CHL, DMS and DMSP (dimethylsulphoniopropionate) vertical profiles are obtained for July, August and September in year 2012. CHL had the higher variation of subsurface concentration maximum (SCM) in July with the lower surface concentration value. DMS had surface higher and subsurface lower profile for the all three months. DMSP also had subsurface high in July. The SCM CHL diurnal variation in the subsurface also can be resulted from diurnal changes in MLD and vertical mixing variations, plus photolysis and wind-driven ventilations. [ABSTRACT FROM AUTHOR]

The interannual changes in ice coverage in the Greenland Sea for the winter (December–April), spring (May– June), summer (July–September), and autumn (October–November) seasons for the period 1950-2018 are considered. The presence of negative linear trends and the polycyclic oscillations of the ice coverage variability for all seasons has been confirmed. Using spectral analysis, the dominant fluctuations from 5 to 22 years were identified. The cross-correlation method allowed us to determine the significant relationship of the Greenland Sea ice coverage with hydrometeorological and astrogeophysical factors. The statistically significant relationship of the ice coverage for a concrete year with similar characteristics for a previous period persisting up to three years had been noted. The highest cross-correlation coefficients were noted in the winter and spring seasons. The ice coverage of the autumn season demonstrates the persistence of the inertia of ice conditions for up to two years. The analysis of correlations with astrogeophysical parameters revealed the closest relationship between the ice coverage and the longitude coordinate of the Earth's pole position, the nutation parameters of the Earth's axis, and the distance between the Earth and the Sun. When constructing the multi-regression equations, we investigated the informativeness of various hydrometeorological and astrogeophysical factors in the models of the ice coverage variability for each season. The following estimates of quality of the models were obtained: correlation coefficients (up to 0.89), determination coefficients (to up 0.80), and a model reliability which depends on the admissible forecast error and includes the mean square deviation of the investigated value) – up to 99%). The informativeness of various factors was estimated and the contribution to the total variance was revealed: hydrometeorological factors – up to 70%; astrogeophysical factors – up to 50%. The obtained statistical equations can be used for the diagnosis and for development of methods for the very-long-term forecast of the Greenland Sea ice coverage.

The East Greenland Polar Front (EGPF) is an important front with strong salinity and temperature gradients in the Nordic Seas. It is formed by the interaction between Arctic-origin and Atlantic-origin water. The variations of EGPF are closely linked with sea ice melting and heat content transport associated with North Atlantic water recirculation. For a three-dimensional (3D) daily analysis, we use the global ocean eddy resolution reanalysis product (GLORYS12V1) from 1993 to 2018 to calculate the salinity and temperature horizontal gradient in the upper ocean and obtain the spatiotemporal distribution and intensity characteristics of EGPF. After assessment, the thresholds of the salinity and temperature fronts are set to 0.04 psu/km and 0.09°C/km, respectively. Compared with satellite observations of sea ice concentration, a significant spatial relationship is observed between the main position of EGPF and the ice edge before the sea ice shrinks to the continental shelf sea area. Affected by the freshening of the Arctic-origin water due to the melting of the sea ice, the intensity and area of EGPF show significant seasonal variations. Against the background of global warming, the sea ice area presents an obvious decreasing trend in the Greenland Sea. The melting of sea ice increased annually every summer from 1998 to 2018. The heat content transport of the Atlantic-origin water has also increased in recent years. The 3D characteristics (intensity and volume) of EGPF as salinity and temperature fronts exhibit increasing trends.

The hydrography of the central Greenland Sea was reconstructed from observations including bottle measurements, Conductivity/ Temperature/ Depth (CTD) measurements, and Argo floats for the period 1950 to 2020. Greenland Sea Deep Water was renewed during bottom-reaching convection prior to the mid-1980s, facilitated by the thermobaric effect. During a period of shallow convection in the late 1980s and early 1990s, a stratification maximum formed and isolated the deep from the intermediate Greenland Sea. As a consequence, convection was limited to depths shallower than 2000 m during the past decades and a new class of intermediate water formed instead of deep water. The initial cause for the formation of the stratification maximum was a near-surface freshwater anomaly. A subsequent, rapid temperature and salinity increase in the upper 2000 m resulted in an overall density reduction of the intermediate water which strengthened the stratification maximum. Along with the transition from formation of deep water to formation of intermediate water, the Greenland Sea became temperature-stratified at intermediate depths. This regime-shift in stratification can be traced to increased temperature and salinity in the inflowing Atlantic-origin Water. Below the stratification maximum, the Greenland Sea Deep Water became warmer and more saline, predominantly caused by lateral mixing with deep water masses from adjacent basins. The hydrographic changes in the Greenland Sea were investigated in the context of a reduction of the sea-ice extent and associated changes in winter heat loss. While interannual variability of convection depth may depend on atmospheric forcing, we found that the decadal variability of water-mass transformation in the Greenland Sea was largely determined by the hydrographic structure of the water column. • We present a novel 70-year long reconstruction of Greenland Sea hydrography. • Bottom-reaching thermobaric convection occurred until the mid-1980s. • After 1985, a mid-depth stratification maximum developed due to near-surface freshening and warming. • The Greenland Sea became temperature-stratified at intermediate depths after 1990. • Reduced sea-ice extent has modified the heat-flux distribution and increased the total heat loss. [ABSTRACT FROM AUTHOR]

The Greenland Sea intermediate waters transported via the Jan Mayen Channel (JMCh) are a significant source for the Iceland-Scotland Overflow Water. Based on hydrographic data collected by a Norway-China survey in 2015 and Argo floats, we classify the water masses of the Greenland Sea outflow and then reveal their distributions in the Norwegian Sea. The Atlantic-origin water produced by density increase during winter in the northern Greenland Sea was an important component of the intermediate waters exported to the Norwegian Sea, accounting for about 30% of the total volume in 2015. The hydrographic data revealed that the major passage of outflow from the Greenland Sea was located in the southern Mohn Ridge in 2015, rather than in the JMCh, as generally recognized. The transport of intermediate waters from the Greenland Sea via the southern Mohn Ridge in the summer of 2015 is estimated to be about 0.8--1.7 Sv. This transport pattern provides a perspective that there exists a multi-passage system of outflow in the JMCh and Mohn Ridge, promoting a stable supply of intermediate waters to the Norwegian Sea. [ABSTRACT FROM AUTHOR]

The ichthyological studies carried out at the shelf of North-Eastern Greenland in 2002–2017 new regions of dwelling of beaked redfish Sebastes mentella were discovered. It is shown that the distribution of underyearlings is not limited to the European shelf, but extends much further to the west, to the deep-water part of the Fram Strait. Juvenile individuals of beaked redfish constantly occur off North-Eastern Greenland, where the branches of the Gulf Stream reach its shelf, and further south to the area of the formation of a circular current in the eastern part of the Greenland Sea and western the Norwegian Sea. It is likely, that this cyclonic system and the cold Greenland Current are an integral part of the feeding and migratory path of larvae, juvenile specimens and adult beaked redfish to the area of its reproduction on the European shelf, as well as in the Irminger Sea. [ABSTRACT FROM AUTHOR]

The results of studies of seasonal and inter-annual variability of the Greenland Sea ice cover are presented for the period from 1950 to 2016. Statistical characteristics of seasonal and inter-annual changes in the ice-covered area were calculated. Three clusters of typical seasonal variability were identified from the whole totality of all seasonal cycles. The first cluster presented a group of seasonal cycles in the period of maximum, the second one – the middle, and the third group – minimum areas of the winter ice cover. The estimates of correlation between changes in the ice areas in winter (February–March) or in summer (August–September) and areas of the following two months of a current year as well as in succeeding years were obtained. Empirical regularity of a variability of the ice cover during the annual cycle was established. This regularity is characterized by an existence of a ‘memory’ in the state of the ice cover, when a prehistory of the ice conditions determines to a certain extent the following phase. Analysis of inter-annual variability of the Greenland Sea ice cover did show a linear negative tendency in both winter and summer ice conditions. One-two year fluctuations were the most pronounced in the spectral density of inter-annual variations in the summer ice conditions. However, fluctuations with a longer period do also exist. With respect to contribution of hydrometeorological factors, the summer ice area is determined: (a) by conditions in the preceding winter, (b) by the atmospheric circulation, and (c) by the influence of warm Atlantic waters (about 20% of the total dispersion). Changes in the winter ice area depend: (a) mainly on the pre-winter state of ices (October–November), (b) on the influence of the Atlantic waters (about 30% of the total dispersion), and (c) on the heat balance and the atmospheric circulation (20% of the total dispersion). The results of this study may be used as a basis for the development of statistical models for analysis and prediction of long-term and climatic changes in the state of the ice cover in the Greenland Sea.

The Greenland Sea gyre is one of the few areas where the water column is ventilated through open ocean convection. This process brings both anthropogenic carbon and oxygen from the atmosphere and surface ocean into the deep ocean, and also makes the Greenland Sea gyre interesting in a global perspective. In this study, a combination of ship- and float-based observations during the period 1986–2016 are analysed. Previous studies have shown warming and salinification of the upper 2000 m until 2011. The extended data record used here shows that this is continuing until 2016. In addition, oxygen concentrations are increasing over the entire period. The changes in temperature, salinity, and especially oxygen have been more pronounced since the turn of the century. This period has also been characterised by deeper wintertime mixed-layer depths, linking the warming, salinification and oxygenation to strengthened ventilation in the Greenland Sea gyre after 2000. The results also demonstrate that the strengthened ventilation can be tied to advection of warmer and more saline surface water from the North Atlantic through the Faroe-Shetland Channel. This advection has led to more saline surface waters in the Greenland Sea gyre, which is contributing to the deeper wintertime mixed layers.

Climate model projections suggest a substantial decrease of sea ice export into the outflow areas of the Arctic Ocean over the 21st century. Fram Strait, located in the Greenland Sea sector, is the principal gateway for ice export from the Arctic Ocean. The consequences of lower sea ice flux through Fram Strait on ocean dynamics and primary production in the Greenland Sea remain unknown. By using the most recent 16 years (2003–2018) of satellite imagery available and hydrographic in situ observations, the role of exported Arctic sea ice on water column stratification and phytoplankton production in the Greenland Sea is evaluated. Years with high Arctic sea ice flux through Fram Strait resulted in high sea ice concentration in the Greenland Sea, stronger water column stratification, and an earlier spring phytoplankton bloom associated with high primary production levels. Similarly, years with low Fram Strait ice flux were associated with a weak water column stratification and a delayed phytoplankton spring bloom. This work emphasizes that sea ice and phytoplankton production in subarctic "outflow seas" can be strongly influenced by changes occurring in the Arctic Ocean. Plain Language Summary: As the Arctic atmosphere and ocean warm, Arctic sea ice continues to decline. The Greenland Sea (to the east of Greenland) is heavily influenced by sea ice leaving the Arctic Ocean. In this study, we address the impacts of sea ice exiting the Arctic on the development of free‐floating microscopic algae in the Greenland Sea. For this, we analyzed 16 years of data from satellite images and autonomous ocean robots. Our results reveal that changes in the quantity of sea ice leaving the Arctic Ocean in spring modify the environment and development of microscopic algae. These algae are important because they capture carbon dioxide and support ocean life; this paper can help to predict how they will respond to the ongoing environmental changes occurring in the Arctic. Key Points: A positive relationship exists between exported Arctic sea ice and the sea ice distribution in the Greenland SeaHigh (low) springtime export of Arctic sea ice may increase (reduce) the stratification of the Greenland BasinA strong (weak) salinity stratification of the Greenland Basin induces an early (late) phytoplankton spring bloom and primary production [ABSTRACT FROM AUTHOR]

Substantial changes have occurred in the Arctic Ocean in the last decades. Not only sea ice has retreated significantly, but also the ocean at middepth showed a warming tendency. By using simulations we identified a mechanism that intensifies the upward trend in ocean heat supply to the Arctic Ocean through Fram Strait. The reduction in sea ice export through Fram Strait induced by Arctic sea ice decline increases the salinity in the Greenland Sea, which lowers the sea surface height and strengthens the cyclonic gyre circulation in the Nordic Seas. The Atlantic Water volume transport to the Nordic Seas and Arctic Ocean is consequently strengthened. This enhances the warming trend of the Arctic Atlantic Water layer, potentially contributing to the Arctic "Atlantification." Our study suggests that the Nordic Seas can play the role of a switchyard to influence the heat budget of the Arctic Ocean. Plain Language Summary: The Arctic sea ice decline is among the key indications of climate change, which has strong impacts on the environment, human beings, and biodiversity. In this paper we found that the Arctic sea ice decline at the surface can even cause Arctic Ocean warming at middepth by intensifying the upward trend of ocean heat supply to the Arctic Ocean through Fram Strait. The Nordic Seas play the role of a switchyard for the involved processes: The sea ice decline reduces the sea ice export through Fram Strait, which further increases the salinity in the Greenland Sea. Consequently, in the Nordic Seas the sea surface height decreases and the gyre circulation strengthens. These changes then increase the Atlantic Water inflow to the Nordic Seas and the Arctic Ocean, causing significant warming in the Atlantic Water layer of the Arctic Ocean. The changes in the ocean heat budget have strong implications on potential feedbacks to sea ice decline through basal melting in a future warming climate. The intensification of the Atlantic Water volume transport through Fram Strait can impact not only the Arctic heat budget but also potentially the nutrient budget and the primary production. Key Points: The decline of Arctic sea ice reduces its export, thus increasing the salinity in Greenland SeaThis reduces the sea surface height and speeds up the gyre circulation in Greenland and Nordic SeasThe consequently enhanced Atlantic Water transport intensifies the warming at Fram Strait and in the Arctic Ocean [ABSTRACT FROM AUTHOR]

The gyres of the Iceland and Greenland Seas are regions of deep-water formation, driven by large ocean-to-atmosphere heat fluxes that have local maxima adjacent to the sea-ice edge. Recently these regions have experienced a dramatic loss of sea ice, including in winter, which begs the question have surface heat fluxes in the adjacent ocean gyres been affected? To address this a set of regional atmospheric climate model simulations has been run with prescribed sea ice and sea surface temperature fields. Three 20-year model experiments have been examined: Icemax, Icemed and Icemin, where the surface fields are set as the year with maximum, median and minimum sea-ice extents respectively. Under conditions of reduced sea-ice extent there is a 15% (19 W m−2) decrease in total wintertime heat fluxes in the Iceland Sea. In contrast, there is an 8% (9 W m−2) increase in heat fluxes in the Greenland Sea primarily due to higher local SSTs. These differences are manifest as changes in the magnitude of high heat flux events (such as cold air outbreaks). In the Iceland Sea, 76% of these events are lower in magnitude during reduced sea-ice conditions. In the Greenland Sea, 93% of these events are higher in magnitude during reduced sea-ice conditions as a result of higher SSTs coincident with retreating sea ice. So, in these experiments, the reduced wintertime sea-ice conditions force a different response in the two seas. In both gyres, large-scale atmospheric circulation patterns are key drivers of high heat flux events. [ABSTRACT FROM AUTHOR]

This study presents a comparison of the sea-ice cover of the whole Arctic Ocean with two arctic sectors of different morphology: the Greenland Sea, as a typical “open sea”, and the Beaufort Sea, as a typical “closed sea”. The study refers to the period January 1996–December 2015 and makes use of the Arctic sea-ice concentration data set produced, on a daily basis, by the Institute of Environmental Physics of the University of Bremen. From the whole Arctic data set, two subsets, covering the Greenland Sea and the Beaufort Sea, were extracted. The extent of sea-ice cover was obtained by the sea-ice area (SIA) parameter, which was computed according to the conventional NASA method. Our analysis shows that the strong summer decline of the Arctic SIA in the last 20 years is not observed in the Greenland Sea (the trend of SIA minimum values is $$0.7 \pm 2.0{\rm{ }}{10^3}\,{\rm{k}}{{\rm{m}}^{\rm{2}}}\,{\rm{yea}}{{\rm{r}}^{ - 1}}$$) while it is even greater in the Beaufort Sea.

Internal waves in the ocean play an important role in turbulence generation due to wave-breaking processes and mixing of the ocean. Airborne radar images of internal waves and ocean eddies north of Svalbard suggested that ocean eddies could generate internal waves. Here, we test this hypothesis using data from a dedicated internal wave experiment in the Greenland Sea. Internal waves with dominant frequencies of 1–3 cycles per hour and amplitudes up to 15 m were observed using three thermistor chains suspended from a drifting array conveniently placed on the ice in a triangle with sides of several km. Analysis shows that internal waves propagated westwards with a speed of about 0.2 m/s and wavelength of 0.4–1.0 km, away from an anticyclonic ocean eddy located just east of the array. This was consistent with the remote-sensing observations of internal waves whose surface signature was imaged by an airborne radar in the western part of this eddy, and with theories that eddies and vortexes can directly generate internal waves. This case study supports our hypothesis that ocean eddies can be the direct sources of internal waves reported here for the first time and not only enhancing the local internal wave field by draining energy from the eddies, as studied previously. The present challenge is to explore the role of eddies as a new source in generating internal waves in the global ocean.

Internal waves in the ocean play an important role in turbulence generation due to wave-breaking processes and mixing of the ocean. Airborne radar images of internal waves and ocean eddies north of Svalbard suggested that ocean eddies could generate internal waves. Here, we test this hypothesis using data from a dedicated internal wave experiment in the Greenland Sea. Internal waves with dominant frequencies of 1–3 cycles per hour and amplitudes up to 15 m were observed using three thermistor chains suspended from a drifting array conveniently placed on the ice in a triangle with sides of several km. Analysis shows that internal waves propagated westwards with a speed of about 0.2 m/s and wavelength of 0.4–1.0 km, away from an anticyclonic ocean eddy located just east of the array. This was consistent with the remote-sensing observations of internal waves whose surface signature was imaged by an airborne radar in the western part of this eddy, and with theories that eddies and vortexes can directly generate internal waves. This case study supports our hypothesis that ocean eddies can be the direct sources of internal waves reported here for the first time and not only enhancing the local internal wave field by draining energy from the eddies, as studied previously. The present challenge is to explore the role of eddies as a new source in generating internal waves in the global ocean. [ABSTRACT FROM AUTHOR]

New marine geophysical data acquired across the partly ice‐covered northern East Greenland continental margin highlight a complex interaction between tectonic and magmatic events. Breakup‐related lava flows are imaged in reflection seismic data as seaward dipping reflectors, which are found to decrease in size both northward and southward from a central point at 75°N. We provide evidence that the magnetic anomaly pattern in the shelf area is related to volcanic phases and not to the presence of oceanic crust. The remnant magnetization of the individual lava flows is used to deduce a relative timing of the emplacement of the volcanic wedges. We find that the seaward dipping reflectors have been emplaced over a period of 2–4 Ma progressively from north to south and from landward to seaward. The new data indicate a major post‐middle Eocene magmatic phase around the landward termination of the West Jan Mayen Fracture Zone. This post‐40‐Ma volcanism likely was associated with the progressive separation of the Jan Mayen microcontinent from East Greenland. The breakup of the Greenland Sea started at several isolated seafloor spreading cells whose location was controlled by rift structures and led to the present‐day segmentation of the margin. The original rift basins were subsequently connected by steady‐state seafloor spreading that propagated southward, from the Greenland Fracture Zone to the Jan Mayen Fracture Zone. Key Points: Polyphase Cenozoic volcanic rifting and consecutive emplacement of breakup‐related lava flows along the northern East Greenland marginBreakup along restricted margin segments is followed by north to south directed progressive opening of the Greenland SeaWidespread post‐middle Eocene (<40 Ma) offshore magmatism, associated with the breakup of the Jan Mayen microcontinent from East Greenland [ABSTRACT FROM AUTHOR]

Multimodel Arctic Ocean "climate response function" experiments are analyzed in order to explore the effects of anomalous wind forcing over the Greenland Sea (GS) on poleward ocean heat transport, Atlantic Water (AW) pathways, and the extent of Arctic sea ice. Particular emphasis is placed on the sensitivity of the AW circulation to anomalously strong or weak GS winds in relation to natural variability, the latter manifested as part of the North Atlantic Oscillation. We find that anomalously strong (weak) GS wind forcing, comparable in strength to a strong positive (negative) North Atlantic Oscillation index, results in an intensification (weakening) of the poleward AW flow, extending from south of the North Atlantic Subpolar Gyre, through the Nordic Seas, and all the way into the Canadian Basin. Reconstructions made utilizing the calculated climate response functions explain ∼50% of the simulated AW flow variance; this is the proportion of variability that can be explained by GS wind forcing. In the Barents and Kara Seas, there is a clear relationship between the wind‐driven anomalous AW inflow and the sea ice extent. Most of the anomalous AW heat is lost to the atmosphere, and loss of sea ice in the Barents Sea results in even more heat loss to the atmosphere, and thus effective ocean cooling. Release of passive tracers in a subset of the suite of models reveals differences in circulation patterns and shows that the flow of AW in the Arctic Ocean is highly dependent on the wind stress in the Nordic Seas. Plain Language Summary: The North Atlantic Current is an extension of the Gulf Stream, which brings warm Atlantic Water northward as the current flows through the Nordic Seas. Eventually, it enters the cold deep Arctic Ocean basins through the Barents Sea and Fram Strait. Nine different numerical ocean ice models have been analyzed and compared in order to investigate (1) their ability to simulate this northward flow of Atlantic Water, (2) its dependence on wind forcing, and (3) its impact on Arctic sea ice. Consistently, in all models, stronger winds in the Greenland Sea result in a stronger northward flow of warm Atlantic Water. The response on ocean circulation occurs from the North Atlantic, through the Nordic Seas and the Barents Sea, to the deep Canadian Basin. The flow of warm Atlantic Water within the Arctic Ocean is thus highly dependent on the wind stress in the Nordic Seas. There is particularly clear response in the Barents and Kara Seas where a wind‐driven anomalous warm inflow drives a smaller sea ice extent and thickness, and an increased heat transfer from the ocean to the atmosphere above. Weaker winds in the Greenland Sea produces weaker flow and hence a larger sea ice extent and thickness. Key Points: Stronger/weaker winds over the Greenland Sea result in stronger/weaker flow of Atlantic Water in the Nordic Seas and into the Arctic OceanIn the Barents Sea there is a linear relationship between Atlantic Water volume and heat transport, surface heat loss, and sea ice extentThere is potential for predictability of the Arctic‐Atlantic circulation based on wind forcing anomalies and climate response functions [ABSTRACT FROM AUTHOR]

Hydrographic measurements from ships, autonomous profiling floats, and instrumented seals over the period 1986–2016 are used to examine the temporal variability in open-ocean convection in the Greenland Sea during winter. This process replenishes the deep ocean with oxygen and is central to maintaining its thermohaline properties. The deepest and densest mixed layers in the Greenland Sea were located within its cyclonic gyre and exhibited large interannual variability. Beginning in winter 1994, a transition to deeper (>500 m) mixed layers took place. This resulted in the formation of a new, less dense class of intermediate water that has since become the main product of convection in the Greenland Sea. In the preceding winters, convection was limited to <300-m depth, despite strong atmospheric forcing. Sensitivity studies, performed with a one-dimensional mixed layer model, suggest that the deeper convection was primarily the result of reduced water-column stability. While anomalously fresh conditions that increased the stability of the upper part of the water column had previously inhibited convection, the transition to deeper mixed layers was associated with increased near-surface salinities. Our analysis further suggests that the volume of the new class of intermediate water has expanded in line with generally increased depths of convection over the past 10–15 years. The mean export of this water mass from the Greenland Sea gyre from 1994 to present was estimated to be 0.9 ± 0.7 Sv (1 Sv ≡ 106 m3 s−1), although rates in excess of 1.5 Sv occurred in summers following winters with deep convection. [ABSTRACT FROM AUTHOR]

The Greenland Sea gyre is one of the few areas where the water column is ventilated through open ocean convection. This process brings both anthropogenic carbon and oxygen from the atmosphere and surface ocean into the deep ocean, and also makes the Greenland Sea gyre interesting in a global perspective. In this study, a combination of ship- and float-based observations during the period 1986-2016 are analysed. Previous studies have shown warming and salinification of the upper 2000 m until 2011. The extended data record used here shows that this is continuing until 2016. In addition, oxygen concentrations are increasing over the entire period. The changes in temperature, salinity, and especially oxygen have been more pronounced since the turn of the century. This period has also been characterised by deeper wintertime mixed-layer depths, linking the warming, salinification and oxygenation to strengthened ventilation in the Greenland Sea gyre after 2000. The results also demonstrate that the strengthened ventilation can be tied to advection of warmer and more saline surface water from the North Atlantic through the Faroe-Shetland Channel. This advection has led to more saline surface waters in the Greenland Sea gyre, which is contributing to the deeper wintertime mixed layers. [ABSTRACT FROM AUTHOR]

The biogeochemistry from a global climate model (Norwegian Earth System Model) has been compared with results from a regional model (NORWECOM.E2E), where the regional model is forced by downscaled physics from the global model. The study should both be regarded as a direct comparison between a regional and its driving global model to investigate at what extent a global climate model can be used for regional studies, and a study of the future climate change in the Nordic and Barents Seas. The study concludes that the global and regional model compare well on trends, but many details are lost when a coarse resolution global model is used to assess climate impact on regional scale. The main difference between the two models is the timing of the spring bloom, and a non-exhaustive nutrient consumption in the global model in summer. The global model has a cold (in summer) and saline bias compared with climatology. This is both due to poorly resolved physical processes and oversimplified ecosystem parameterization. Through the downscaling the regional model is to some extent able to alleviate the bias in the physical fields, and the timing of the spring bloom is close to observations. The summer nutrient minimum is one month early. There is no trend in future primary production in any of the models, and the trends in modelled pH and Ω Ar are also the same in both models. The largest discrepancy in the future projection is in the development of the CO2 uptake, where the regional suggests a slightly reduced uptake in the future. [ABSTRACT FROM AUTHOR]

Abstract The Arctic is a unique and fragile ecosystem that needs to be preserved and protected. Despite its remoteness, plastic pollution has been documented in this region. In the coming years, it is likely to worsen since, with climate changes and the opening of new shipping routes, the human presence is going to increase in the whole area. Here, we investigated the presence of microplastics (MPs) in sub-surface water and in two mid-trophic level Arctic fishes collected off Northeast Greenland: the demersal bigeye sculpin, Triglops nybelini , and the pelagic polar cod, Boreogadus saida. Plastics debris were found in the water samples at a concentration of 2.4 items/m3 ±0.8 SD which is higher than in most seas at lower latitudes. Both fish species had eaten MPs with different proportion among the species, 34% for T. nybelini (n = 71) and 18% for B. saida (n = 85). The significant difference in the occurrence of MPs between the two species is likely a consequence of their feeding behavior and habitat. Polyethylene was the main plastic polymer for water samples (41%, n = 17) and polyester (34%, n = 156) for fish samples as analyzed by Fourier Transformed Infrared (FT-IR) spectroscopy. Our data underscore that the Arctic regions are turning into a hotspot for plastic pollution, and this calls urgently for precautionary measures. Graphical abstract Image 1 Highlights • Plastic debris was found at each sampling stations with an average abundance of 2.4 items/m3 (±0.8 SD). • 25% of investigated fish ingested plastics. • Need of unique and standardized MP protocols for reliable reporting. [ABSTRACT FROM AUTHOR]

In seasonal ice zones (SIZs), such as the one of the Greenland Sea, the sea ice growth in winter and subsequent melting in summer influence the phytoplankton activity. However, studies assessing phytoplankton activities over complete annual cycles and at a fine temporal resolution are lacking in this environment. Biogeochemical‐Argo floats, which are able to sample under the ice, were used to collect physical and biogeochemical data along vertical profiles and at 5‐day resolution during two complete annual cycles in the Greenland Sea SIZ. Three phytoplankton activity phases were distinct within an annual cycle: one under ice, a second at the ice edge, and a third one around an open‐water subsurface chlorophyll maximum. As expected, the light and nitrate availabilities controlled the phytoplankton activity and the establishment of these phases. On average, most of the annual net community production occurred equally under ice and at the ice edge. The open‐water subsurface chlorophyll maximum phase contribution, on the other hand, was much smaller. Phytoplankton biomass accumulation and production thus occur over a longer period than might be assumed if under ice blooms were neglected. This also means that satellite‐based estimates of phytoplankton biomass and production in this SIZ are likely underestimated. Simulations with the Arctic‐based physical‐biologically coupled SINMOD model suggest that most of the annual net community production in this SIZ results from local processes rather than due to advection of nitrate from the East Greenland and Jan Mayen Currents. Key Points: In the seasonal ice zone, significant phytoplankton activity occurs under ice earlier in the seasonAt the ice edge, a high phytoplankton biomass is present around a subsurface chlorophyll maximum feature that persists into summerHalf of the annual Net Community Production occurs under ice and the other half at the ice edge [ABSTRACT FROM AUTHOR]

Abstract: Atlantic Water (AW) transported from the Nordic Seas is the major source of oceanic heat to the Arctic Ocean. Based on results from the TOPAZ reanalysis, a regional coupled ice‐ocean data assimilation system, we show that interannual variability of AW temperature in the Fram Strait (FS) is associated with the strength of the Greenland Sea gyre (GSG) circulation. The response of the GSG to the anomalous wind stress curl over the Nordic Seas modifies the AW inflow and thus influences the variability of AW temperature in the FS. A stronger (weaker) GSG circulation increases (decreases) the AW flow speed toward FS, leading to increased (decreased) oceanic heat content and higher (lower) AW temperature therein. This implies that the Nordic Seas circulation is not only a passive conduit of AW, but its response to overlying atmospheric variability can also largely influence the AW temperature in the FS by modifying the transport of AW. [ABSTRACT FROM AUTHOR]

During summer 2014 and summer 2015 two autonomous Seagliders were operated over several months close to the ice edge of the East Greenland Current to capture the near-surface fresh water distribution in the western Greenland Sea. The mission 2015 included an excursion onto the East Greenland Shelf into the Norske Trough. Temperature, salinity and drift data were obtained in the upper 500 to 1000 m with high spatial resolution. At AWI the data processing for these glider measurements was conducted. The first part consists of the Seaglider Toolbox from the University of Each Anglia, the second was exclusively composed for the data from the Greenland Sea. The final hydrographic, position and drift data sets can be downloaded from https://doi.org/10.1594/PANGAEA.893896. [ABSTRACT FROM AUTHOR]

The hypothesis that Arctic tidal pools provide environmental conditions suitable for calcifiers during summer, thereby potentially providing refugia for calcifiers in an acidifying Arctic Ocean, was tested on the basis of measurements conducted during two midsummers (2014 and 2016) in tidal pools colonised by a community composed of macroalgae and calcifiers in Disko Bay, Greenland (69° N). The tidal pools exhibited steep diurnal variations in temperature from a minimum of about 6 °C during the night to a maximum of almost 18 °C in the afternoon, while the temperature of the surrounding shore water was much lower, typically in the range 3 to 8 °C. O2 concentrations in the tidal pools were elevated relative to those in the adjacent open waters, by up to 11 mg O2 L−1, and exhibited heavy super-saturation (up to > 240%) during daytime emersion, reflecting intense and sustained photosynthetic rates of the tidal macroalgae. The intense photosynthetic activity of the seaweeds resulted in the drawdown of pCO2 concentrations in the pools during the day to levels down to average (±SE) values of 66 ± 18 ppm, and a minimum recorded value of 14.7 ppm, corresponding to pH levels as high as 8.69 ± 0.08, as compared to CO2 levels of 256 ± 4 and pH levels of 8.14 ± 0.01 in the water flooding the pools during high tide. The corresponding Ωarag reached 5.04 ± 0.49 in the pools as compared to 1.55 ± 0.02 in the coastal waters flooding the pools. Net calcification averaged 9.6 ± 5.6 μmol C kg−1 h−1 and was strongly and positively correlated with calculated net ecosystem production rates, which averaged 27.5 ± 8.6 μmol C kg−1 h−1. Arctic tidal pools promote intense metabolism, creating conditions suitable for calcification during the Arctic summer, and can, therefore, provide refugia from ocean acidification to vulnerable calcifiers as extended periods of continuous light during summer are conducive to suitable conditions twice a day. Meroplankton larvae are exposed to ocean acidification until they settle in vegetated tidal pools, where they benefit from the protection offered by the “macroalgae-carbonate saturation state” interaction favouring calcification rates. [ABSTRACT FROM AUTHOR]

Liu, X. and Zhang, L., 2018. Study on optimization of sea ice concentration with adjoint method. In: Wang, D. and Guido-Aldana, P.A. (eds.), Select Proceedings from the 3rd International Conference on Water Resource and Environment (WRE2017). Journal of Coastal Research, Special Issue No. 84, pp. 44–50. Coconut Creek (Florida), ISSN 0749-0208. Obtaining initial sea ice concentration (SIC) values with high accuracy that are consistent with other models have been a hot topic in both sea ice prediction and sea ice modeling studies. Here, an ocean-sea ice coupled numerical model and its adjoint code have been utilized to carry out numerical experiments to optimize the initial SIC values. In the experiments, the cost function was defined as the difference between the SIC values from the reanalysis dataset and the modeled results. The gradient of cost function, relative to SIC and other model variables, was computed by the adjoint model, and a linear search algorithm was employed to optimize the SIC values by minimizing the cost function. The influences of the weight coefficients of the cost function, the extent of the geographical region, and the seawater temperature and sea ice thickness initial values on the optimization results have been analyzed. The weight coefficients of the cost function had little effect on the SIC distribution pattern but substantial influence on the SIC values. The optimized SIC in the Greenland Sea, Okhotsk Sea, and the Arctic Ocean, with a constant weight coefficient, is better than that with variable weight coefficients. The errors in the initial model fields, other than SIC, may deteriorate the overall result, implying that optimizing multiple model fields simultaneously may improve the optimization effect. Decreasing the size of the geographical region for optimization does not improve the SIC optimization results substantially. Compared to the results from a global cost function, the Barents Sea SIC values from a northern hemispheric cost function are poorly optimized. [ABSTRACT FROM AUTHOR]

The sea-to-air flux of dimethylsulphide (DMS) is one of the major sources of marine biogenic aerosol, and can have an important radiative impact on climate, especially in the Arctic Ocean. Satellite-derived aerosol optical depth (AOD) is used as a proxy for aerosol burden which is dominated by biogenic aerosol during summer and autumn. The spring sea ice melt period is a strong source of aerosol precursors in the Arctic. However, high aerosol levels in early spring are likely related to advection of continental pollution from the south (Arctic haze). Higher AOD was generally registered in the southern part of the study region. Sea ice concentration (SIC) and AOD were positively correlated, while cloud cover (CLD) and AOD were negative correlation. The seasonal peaks of SIC and CLD were both one month ahead of the peak in AOD. There is a strong positive correlation between AOD and SIC. Melting ice is positively correlated with chlorophyll a (CHL) almost through March to September, but negatively correlated with AOD in spring and early summer. Elevated spring and early summer AOD most likely were influenced by combination of melting ice and higher spring wind in the region. The peak of DMS flux occurred in spring due to the elevated spring wind and more melting ice. DMS concentration and AOD were positively correlated with melting ice from March to May. Elevated AOD in early autumn was likely related to the emission of biogenic aerosols associated with phytoplankton synthesis of DMS. The DMS flux would increase more than triple by 2100 in the Greenland Sea. The significant increase of biogenic aerosols could offset the warming in the Greenland Sea. [ABSTRACT FROM AUTHOR]