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Abstract The North Water Polynya (NOW) is one of the most productive biological regions in the Arctic with high importance to Inuit and Greenlandic communities. To provide insights into the potential changes of this region as global temperatures rise, we investigated the sea ice and physical and biological oceanic responses of the NOW to low (2°C) and high (>3.5°C) levels of warming using the Community Earth System Model, version 1. As global temperatures increase, sea ice production decreases, spring open water area increases, and summer open water areas in the NOW region connect with open water in central Baffin Bay earlier in the melt season. These sea ice changes contribute to increased stratification, which in turn leads to increased concentrations of nutrient-rich West Greenland Irminger Waters at depth while decreasing surface nutrient concentrations. At low warming levels in the eastern NOW region, warmer water temperatures increase phytoplankton growth rates despite the decrease in surface nutrients, leading to an increase in peak primary production relative to the historical period. In contrast, for high warming in both the eastern and western NOW regions, biological primary production decreases, despite the warmer water temperatures, because increased stratification and decreased surface nutrient concentrations limit phytoplankton production. For all assessed warming levels, changing phytoplankton community composition drives a loss of ecosystem productivity at higher trophic levels. Internal variability plays a negligible role in driving these future sea ice and ocean changes, highlighting the importance of limiting further global temperature increases to avoid large changes to the NOW ecosystem. Significance StatementThe North Water Polynya (NOW) is one of the most productive biological regions in the Arctic with high importance to Inuit and Greenlandic communities. In this paper, we explore how sea ice and physical and biological ocean conditions will change under low (2°C) and high (>3.5°C) levels of global warming. 

ABSTRACT MotivationHere, we make available a second version of the BioTIME database, which compiles records of abundance estimates for species in sample events of ecological assemblages through time. The updated version expands version 1.0 of the database by doubling the number of studies and includes substantial additional curation to the taxonomic accuracy of the records, as well as the metadata. Moreover, we now provide an R package (BioTIMEr) to facilitate use of the database. Main Types of Variables IncludedThe database is composed of one main data table containing the abundance records and 11 metadata tables. The data are organised in a hierarchy of scales where 11,989,233 records are nested in 1,603,067 sample events, from 553,253 sampling locations, which are nested in 708 studies. A study is defined as a sampling methodology applied to an assemblage for a minimum of 2 years. Spatial Location and GrainSampling locations in BioTIME are distributed across the planet, including marine, terrestrial and freshwater realms. Spatial grain size and extent vary across studies depending on sampling methodology. We recommend gridding of sampling locations into areas of consistent size. Time Period and GrainThe earliest time series in BioTIME start in 1874, and the most recent records are from 2023. Temporal grain and duration vary across studies. We recommend doing sample‐level rarefaction to ensure consistent sampling effort through time before calculating any diversity metric. Major Taxa and Level of MeasurementThe database includes any eukaryotic taxa, with a combined total of 56,400 taxa. Software Formatcsv and. SQL. 

Abstract Freshwater from the Arctic participates in the globally important Atlantic Meridional Overturning Circulation (AMOC). We use high‐resolution, in situ observations of dissolved organic matter (DOM) fluorescence to trace the origins of freshwater and organic carbon in the densest component of the AMOC, namely Denmark Strait Overflow Water (DSOW). We find a distinct terrestrial DOM signal in DSOW and trace it upstream to the Siberian shelves in the Arctic Ocean. This implies a riverine origin of freshwater in DSOW. We estimate that the Siberian Shelf water contribution constitutes approximately 1% of DSOW. Ocean circulation modeling confirms the inferred pathway and highlights Denmark Strait as an important location for the entrainment of the riverine signal into DSOW. Our proposed method can be deployed on a range of observing systems to elucidate freshwater dispersion across the Arctic and subarctic, thereby contributing to the broader discussion on freshwater impacts and organic carbon sequestration in the AMOC. 

Abstract Baffin Bay is the travel destination of most icebergs calving from west Greenland. They commonly follow the bay's cyclonic circulation and might end up far south along the coast of Newfoundland and Labrador, where many shipping routes converge. Given the hazard that icebergs pose to marine transportation, understanding their distribution is fundamental. One of the forces driving iceberg drift arises from the presence of sea ice. Observations in the Southern Ocean indicate that icebergs get locked in thick and concentrated sea ice. We present observations that support the occurrence of this sea ice locking mechanism (SIL) in Baffin Bay as well. Most iceberg models, however, represent the sea ice force over an iceberg as a simple drag force. Here, we implement a new parameterization in the iceberg module of the Nucleus for European Modeling of the Ocean (NEMO‐ICB) to represent SIL. We show that, by using this new parameterization, icebergs are more likely to travel outside of the Baffin Island Current during winter, which is supported by satellite observations. There is a slight improvement in the representation of iceberg severity along the coast of Newfoundland and Labrador and a slight shift of iceberg melt toward this region and Lancaster Sound/Hudson Strait. Although the impacts of icebergs on sea ice are still not represented, and targeted observations are needed for model calibration regarding sea ice concentration thresholds from which icebergs get locked, we are confident that this model improvement takes iceberg modeling one step forward toward reality. 

Abstract This study quantifies the overturning circulation in the Arctic Ocean and associated heat transport (HT) and freshwater transport (FWT) from October 2004 to May 2010 based on hydrographic and current observations. Our main data source consists of 1165 moored instrument records in the four Arctic main gateways: Davis Strait, Fram Strait, Bering Strait, and the Barents Sea Opening. We employ a box inverse model to obtain mass and salt balanced velocity fields, which are then used to quantify the overturning circulation as well as HT and FWT. Atlantic Water is transformed into two different water masses in the Arctic Ocean at a rate of 4.3 Sv (1 Sv ≡ 10⁶m³s⁻¹). Combined with 0.7 Sv of Bering Strait inflow and 0.15 Sv of surface freshwater flux, 2.2 Sv flows back to the south through Davis Strait and western Fram Strait as the upper limb of the overturning circulation, and 2.9 Sv returns southward through Fram Strait as the lower limb of the overturning. The Arctic Ocean imports heat of 180 ± 57 TW (long-term mean ± standard deviation of monthly means) with a methodological uncertainty of 20 TW and exports FW of 156 ± 91 mSv with an uncertainty of 61 mSv over the 6 years with a potential offset of ∼30 mSv. The HT and FWT have large seasonalities ranging between 110 and 260 TW (maximum in winter) and between 40 and 260 mSv (maximum in winter), respectively. The obtained overturning circulation and associated HT and FWT presented here are vital information to better understand the northern extent of the Atlantic meridional overturning circulation. 

Abstract. The Davis Strait is one of two key Arctic gateways, where waters derived from the Atlantic flow northward and exchange with Arctic-origin waters flowing southward. This interaction may play a crucial role in shaping the formation of deep water masses in the subpolar North Atlantic. This study employs observations from 2022 and 2024 of the two artificial radionuclides 129I and 236U measured in Baffin Bay, Davis Strait and the Labrador Sea. Samples were collected during three expeditions: the AZOMP occupation of the AR7W Line in May 2022, the Davis Strait Observation Programme in October 2022, and the Amundsen Expedition as part of the Transforming Climate Action programme in September–October 2024. By defining the characteristic 129I and 236U concentrations of the main inflowing water masses (endmembers), we examined the distribution, origin and formation of key Baffin Bay water masses. This approach also allowed us to quantify the contribution of Transition Water to the formation of Labrador Sea Water (LSW) and North East Atlantic Deep Water (NEADW). Our results reveal a substantial contribution of West Greenland Shelf Water to Arctic Water on the surface of central Baffin Bay, accounting for approximately 30 %. High 236U identified a previously unknown pathway of Arctic-Atlantic-derived waters entering Baffin Bay via Lancaster Sound, contributing 40–50 % to the formation of Transition Water. In contrast, cold Arctic Water appears to originate mainly from Nares Strait, with contributions of Arctic-Atlantic Water outflowing Nares Strait reaching up to 35 %. Notably, the contribution of fresh Transition Water to the formation of LSW was significant, exceeding 30 %. However, the binary mixing model showed limitations in quantifying the origin of NEADW due to low tracer concentrations and the likely influence of multiple water mass sources. This study offers novel insights into the origin and transformation of waters in Baffin Bay and the Labrador Sea and enhances our understanding of the complex interactions between the Arctic Ocean and the subpolar North Atlantic. 

Information on marine bird abundance and distribution at sea is required to identify important habitat for protection, mitigate pressures from human activities, and understand the role of seabirds in marine food webs. Arctic waters support millions of marine birds, including globally significant numbers of some species, but the remote location coupled with the financial costs of research and monitoring in this region limit our ability to quantify marine habitat use. We used standardized survey data collected from vessels of opportunity during 2007-2023 to describe the distribution and abundance of marine birds in eastern Canadian Arctic waters and to examine the relative contribution of data collected from two primary platform types: research vessels and cruise ships. Northern Fulmars Fulmarus glacialis, Thick-billed Murres Uria lomvia, Black-legged Kittiwakes Rissa tridactyla, and Dovekies Alle alle accounted for 92% of the sightings. The survey area covered by research vessels was 3.5 times greater than that covered by cruise ships, but there was minimal (< 1%) spatial overlap between the two platform types. Cruise ships travelled closer to shore and in shallower water than research vessels, including areas close to major colonies during the breeding season, which resulted in higher densities of birds observed. In addition to providing access to unique survey areas, cruise ships presented opportunities to engage tourists in the process of science and the outcomes of biodiversity monitoring programs. Large-scale monitoring programs that include boat-based surveys from a variety of platform types and collaboration among multiple organizations will remain important for defining marine bird habitat use in an area where human impacts are increasing as sea ice cover declines. 

Systematic surveys of marine birds from ships were first conducted by the Canadian Wildlife Service (CWS) in Atlantic Canada in 1965, and then expanded to the Canadian Arctic in 1969 under PIROP (Programme intégré de recherches sur les oiseaux pélagiques). PIROP surveys ended in 1992, then resumed in 2006 under the Eastern Canada Seabirds at Sea (ECSAS) program with an updated survey protocol. Surveys under both monitoring programs were conducted from a variety of ship types engaged in scientific, transport, and supply activities, totalling over 120,000 km within sub-Arctic and Arctic Canada waters and over a million marine birds observed, primarily northern fulmar (Fulmarus glacialis), black-legged kittiwake (Rissa tridactyla), thick-billed murre (Uria lomvia), and dovekie (Alle alle). The data collected inform offshore ecological inquiries, environmental impact reviews, mortality estimates from accidental oil releases, and define areas in need of protection. Although surveys were designed to quantify seabird distribution within the waters of eastern Canada, the data also include sightings of non-avian taxa that are made publicly available. Long-term and large-scale monitoring programs will remain essential for assessing the status and health of Canada’s marine birds, including surveys that take place at sea where these species spend most of their time. 

The Davis Strait observing system was established in 2004 to advance understanding of the role of Arctic – sub-Arctic interactions in the climate system by collecting sustained measurements of physical, chemical and biological variability at one of the primary gateways that connect the Arctic and subpolar oceans. Efforts began as a collaboration between researchers at the University of Washington’s Applied Physics Laboratory and the Canadian Department of Fisheries and Ocean’s Bedford Institute of Oceanography, but has grown to include researchers from the Greenland Institute of Natural Resources, Greenland Climate Institute, Danish Technological University, University of Alberta and University of Colorado, Boulder. The project is a component of the NSF Arctic Observing and Atlantic Meridional Overturning Networks, and the international Arctic-Subarctic Ocean Flux (ASOF) program, Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP), Global Ocean Acidification Observing Network (GOA-ON), Arctic Monitoring Assessment Programme (AMAP) and OceanSITES system. A mooring array spanning the entire Davis Strait has been in place nearly continuously since September 2004 as part of the Davis Strait observing system, collecting year-round measurements of temperature, salinity and velocity extending to the sea surface/ice-ocean interface. The mooring typically included 14 moorings, 4 on each shelf and 6 in the center of the strait, that are recovered and data offloaded each autumn. Exact mooring location, instrumentation, and deployment duration varied slightly over time. This dataset consists of Level 2 data from the Davis Strait mooring array. Each file contains data from a single sensor (e.g., MicroCAT temperature and salinity measurements or ADCP velocity measurements) at one mooring site collected during a single deployment (typically one year long). Files also include quality control flags. More details about the project can be found at https://iop.apl.washington.edu/project.php?id=davis. 

Arctic Ocean gateway fluxes play a crucial role in linking the Arctic with the global ocean and affecting climate and marine ecosystems. We reviewed past studies on Arctic–Subarctic ocean linkages and examined their changes and driving mechanisms. Our review highlights that radical changes occurred in the inflows and outflows of the Arctic Ocean during the 2010s. Specifically, the Pacific inflow temperature in the Bering Strait and Atlantic inflow temperature in the Fram Strait hit record highs, while the Pacific inflow salinity in the Bering Strait and Arctic outflow salinity in the Davis and Fram straits hit record lows. Both the ocean heat convergence from lower latitudes to the Arctic and the hydrological cycle connecting the Arctic with Subarctic seas were stronger in 2000–2020 than in 1980–2000. CMIP6 models project a continuing increase in poleward ocean heat convergence in the 21st century, mainly due to warming of inflow waters. They also predict an increase in freshwater input to the Arctic Ocean, with the largest increase in freshwater export expected to occur in the Fram Strait due to both increased ocean volume export and decreased salinity. Fram Strait sea ice volume export hit a record low in the 2010s and is projected to continue to decrease along with Arctic sea ice decline. We quantitatively attribute the variability of the volume, heat, and freshwater transports in the Arctic gateways to forcing within and outside the Arctic based on dedicated numerical simulations and emphasize the importance of both origins in driving the variability.