Nordic Seas Heat Loss, Atlantic Inflow, and Arctic Sea Ice Cover Over the Last Century

Abstract

Poleward ocean heat transport is a key process in the earth system. We detail and review the northward Atlantic Water (AW) flow, Arctic Ocean heat transport, and heat loss to the atmosphere since 1900 in relation to sea ice cover. Our synthesis is largely based on a sea ice‐ocean model forced by a reanalysis atmosphere (1900–2018) corroborated by a comprehensive hydrographic database (1950–), AW inflow observations (1996–), and other long‐term time series of sea ice extent (1900–), glacier retreat (1984–), and Barents Sea hydrography (1900–). The Arctic Ocean, including the Nordic and Barents Seas, has warmed since the 1970s. This warming is congruent with increased ocean heat transport and sea ice loss and has contributed to the retreat of marine‐terminating glaciers on Greenland. Heat loss to the atmosphere is largest in the Nordic Seas (60% of total) with large variability linked to the frequency of Cold Air Outbreaks and cyclones in the region, but there is no long‐term statistically significant trend. Heat loss from the Barents Sea (∼30%) and Arctic seas farther north (∼10%) is overall smaller, but exhibit large positive trends. The AW inflow, total heat loss to the atmosphere, and dense outflow have all increased since 1900. These are consistently related through theoretical scaling, but the AW inflow increase is also wind‐driven. The Arctic Ocean CO2 uptake has increased by ∼30% over the last century—consistent with Arctic sea ice loss allowing stronger air‐sea interaction and is ∼8% of the global uptake.

Separating Annual, Interannual and Regional Change in Sea Surface Temperature in the Northeastern Atlantic and Nordic Seas

“…The increased ocean heat transport as represented by the shift in EOF1 in 2000 and the de-seasoned EOF model (Figure S2 in Supporting Information S1), the "switching" role of the SPG and increased AW inflow with the NIIC, collectively suggest an increase in the oceanic heat transport to the Nordic Seas over the 1979-2020 period. These findings are aligned with a suite of recent studies on the heat budget of the Nordic Seas recently reviewed by Smedsrud et al (2022) and provide a separation of the response in SST into independent underlying factors. Increases in AW inflow in part contradict evidence for decreases in Atlantic meridional overturning circulation (AMOC) (e.g., Smeed et al, 2018), which are based on deepwater moorings further south.…”

“…Strong seasonal variability is also evident in the annual build-up and melt of sea-ice. Summertime sea-ice melt along the east Greenland shelf absorbs considerable amounts of latent heat, and releases cold, fresh waters initially lowering summer SST in the western part of the Nordic Seas (Smedsrud et al, 2022). This is reflected in the high frequency signal captured in EOF3 (Figure 6).…”

A Synthesis of the Upper Arctic Ocean Circulation During 2000–2019: Understanding the Roles of Wind Forcing and Sea Ice Decline

“…We note that this paper does not cover all aspects of the Arctic Ocean dynamics. Recently some other Arctic Ocean topics have also been reviewed, including ocean circulation dynamics in general (Timmermans and Marshall, 2020), freshwater in the 2010s (Solomon et al, 2021), ocean heat transports in relation to Arctic sea ice (Docquier and Koenigk, 2021;Smedsrud et al, 2022), and Arctic Atlantification and Borealization (Polyakov et al, 2020a;Ingvaldsen et al, 2021).…”

State of the Climate in 2021

“…5.6d). The cooling trend (~−0.06°C yr −1 ) in mean August SSTs in the north-central Barents Sea region remains a notable exception (Timmermans et al 2020), although the cooling trend is not observed for most other months, nor for other parts of the Barents Sea (Lind et al 2018;Smedsrud et al 2022). Further, in this region Barents Sea waters contact cooler, fresher Arctic waters, and shifts in this boundary complicate interpretation of trends (see Barton et al 2018).…”