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1. Nordic Seas Hydrography in the Context of Arctic and North Atlantic Ocean Dynamics

   https://doi.org/10.1175/JPO-D-20-0071.1  

   Kenigson, J. S.; Timmermans, M.-L. (January 2021, Journal of Physical Oceanography)

   null (Ed.)

   Abstract The hydrography of the Nordic seas, a critical site for deep convective mixing, is controlled by various processes. On one hand, Arctic Ocean exports are thought to freshen the North Atlantic Ocean and the Nordic seas, as in the Great Salinity Anomalies (GSAs) of the 1970s–1990s. On the other hand, the salinity of the Nordic seas covaries with that of the Atlantic inflow across the Greenland–Scotland Ridge, leaving an uncertain role for Arctic Ocean exports. In this study, multidecadal time series (1950–2018) of the Nordic seas hydrography, Subarctic Front (SAF) in the North Atlantic Ocean [separating the water masses of the relatively cool, fresh Subpolar Gyre (SPG) from the warm, saline Subtropical Gyre (STG)], and atmospheric forcing are examined and suggest a unified view. The Nordic seas freshwater content is shown to covary on decadal time scales with the position of the SAF. When the SPG is strong, the SAF shifts eastward of its mean position, increasing the contribution of subpolar relative to subtropical source water to the Atlantic inflow, and vice versa. This suggests that Arctic Ocean fluxes primarily influence the hydrography of the Nordic seas via indirect means (i.e., by freshening the SPG). Case studies of two years with anomalous NAO conditions illustrate how North Atlantic Ocean dynamics relate to the position of the SAF (as indicated by hydrographic properties and stratification changes in the upper water column), and therefore to the properties of the Atlantic inflow and Nordic seas. 

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2. On the Origin of Water Masses in the Beaufort Gyre

   https://doi.org/10.1029/2019JC015022  

   Kelly, S. J.; Proshutinsky, A.; Popova, E. K.; Aksenov, Y. K.; Yool, A. (July 2019, Journal of Geophysical Research: Oceans)

   Abstract The Beaufort Gyre is a key feature of the Arctic Ocean, acting as a reservoir for freshwater in the region. Depending on whether the prevailing atmospheric circulation in the Arctic is anticyclonic or cyclonic, either a net accumulation or release of freshwater occurs. The sources of freshwater to the Arctic Ocean are well established and include contributions from the North American and Eurasian Rivers, the Bering Strait Pacific water inflow, sea ice meltwater, and precipitation, but their contribution to the Beaufort Gyre freshwater accumulation varies with changes in the atmospheric circulation. Here we use a Lagrangian backward tracking technique in conjunction with the 1/12‐degree resolution Nucleus for European Modelling of the Ocean model to investigate how sources of freshwater to the Beaufort Gyre have changed in recent decades, focusing on increase in the Pacific water content in the gyre between the late 1980s and early 2000s. Using empirical orthogonal functions we analyze the change in the Arctic oceanic circulation that occurred between the 1980s and 2000s. We highlight a “waiting room” advective pathway that was present in the 1980s and provide evidence that this pathway was caused by a shift in the center of Ekman transport convergence in the Arctic. We discuss the role of these changes as a contributing factor to changes in the stratification, and hence potentially the biology, of the Beaufort Gyre region. 

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3. The Arctic Ocean's Beaufort Gyre

   https://doi.org/10.1146/annurev-marine-032122-012034  

   Timmermans, Mary-Louise; Toole, John M. (January 2023, Annual Review of Marine Science)

   The Arctic Ocean's Beaufort Gyre is a dominant feature of the Arctic system, a prominent indicator of climate change, and possibly a control factor for high-latitude climate. The state of knowledge of the wind-driven Beaufort Gyre is reviewed here, including its forcing, relationship to sea-ice cover, source waters, circulation, and energetics. Recent decades have seen pronounced change in all elements of the Beaufort Gyre system. Sea-ice losses have accompanied an intensification of the gyre circulation and increasing heat and freshwater content. Present understanding of these changes is evaluated, and time series of heat and freshwater content are updated to include the most recent observations. 

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4. Can the Marked Arctic Ocean Freshwater Content Increases of the Last Two Decades Be Explained Within Observational Uncertainty?

   https://doi.org/10.1029/2024JC021061  

   Le_Bras, Isabela_Alexander‐Astiz; Timmermans, Mary‐Louise (February 2025, Journal of Geophysical Research: Oceans)

   Abstract The freshwater content of the Arctic Ocean has increased dramatically in the last two decades, particularly in the Beaufort Gyre. However, quantifying the sources of this change is an observational challenge and has historically been limited by methodological differences across studies. Here we derive observation‐based freshwater budgets from volume and mass budgets for the Arctic Ocean and the Beaufort Gyre from 2003 to 2020. Our budgets include all sources and sinks (river runoff, precipitation minus evaporation, land ice melt, sea ice export, sea ice melt, and ocean fluxes) as well as volume and mass storage terms measured by satellite. We find that Arctic freshwater changes are dominated by changes in the Beaufort Gyre, and we reconcile this with previous studies that argue for freshwater compensation between the Beaufort Gyre and the rest of the Arctic. We use inverse methods to close the volume and mass budgets within observational uncertainty and link the observed Arctic freshwater changes to the sources and sinks. Our budget analysis demonstrates that small changes to the ocean fluxes (smaller than we can measure) can account for all freshwater storage changes in the Arctic, highlighting the need for more careful accounting and detailed ocean observations in this rapidly changing environment. 

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5. Spinning ice floes reveal intensification of mesoscale eddies in the western Arctic Ocean

   https://doi.org/10.1038/s41598-022-10712-z  

   Manucharyan, Georgy E.; Lopez-Acosta, Rosalinda; Wilhelmus, Monica M. (December 2022, Scientific Reports)

   Abstract Under-ice eddies are prevalent in the major circulation system in the western Arctic Ocean, the Beaufort Gyre. Theoretical studies hypothesize that the eddy-driven overturning and the ice-ocean drag are crucial mechanisms of the gyre equilibration in response to atmospheric winds. However, due to severe weather conditions and limitations of remote sensing instruments, there are only sparse eddy observations in the ice-covered Arctic Ocean. Hence, the evolution of the under-ice eddy field, its impact on the gyre variability, and their mutual response to the ongoing Arctic warming remain uncertain. Here, we infer the characteristics of the under-ice eddy field by establishing its tight connection to the angular velocities of isolated spinning sea ice floes in marginal ice zones. Using over two decades of satellite observations of marginal ice zones in the western Arctic Ocean, we identified and tracked thousands of floes and used idealized eddy modeling to infer the interannual evolution of the eddy energetics underneath the ice. We find that the eddy field is strongly correlated to the strength of the Beaufort Gyre on interannual timescales, which provides the major observational evidence consistent with the hypothesis of the gyre equilibration by eddies. The inferred trends over the past two decades signify that the gyre and its eddy field have been intensifying as the sea ice cover has been declining. Our results imply that with continuing sea ice decline, the eddy field and the Beaufort Gyre will keep intensifying and leading to enhanced transport of freshwater and biogeochemical tracers. 

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