Atlantic Water Heat Transport Variability in the 20th Century Arctic Ocean From a Global Ocean Model and Observations

Abstract

Northward ocean heat transport and its variability influence the Arctic sea ice cover, contribute to surface warming or cooling, or simply warm or cool the Arctic Ocean interior. A simulation with the forced global ocean model NorESM20CR, aided by hydrographic observations since 1900, show large decadal fluctuations in the ocean heat transport, with the largest variations in the Atlantic sector. The simulated net poleward ocean heat transport over the last century is about 68 TW, and 88% of this occurs in the Barents Sea Opening (45 TW) and the Fram Strait (15 TW). Typical variations are 40 TW over time scales between 5 and 10 years, related to thermohaline and wind stress forcings. The mean heat transport in the Davis Strait is about 10 TW, and less than 5 TW flows north in the Bering Strait. The core temperature of the Atlantic Water (AW) entering the Arctic Ocean has increased in recent decades, consistent with an ongoing expansion of the Atlantic domain (Atlantification), but earlier warm events are also documented. The temperature of the northward‐flowing AW thus plays a vital role, with decadal variations of around 0.5 ∘C. The Nordic Seas atmosphere contributes with thermodynamic forcing, dampening the advected heat anomalies. In the Barents Sea, variations in the inflow volume flux dominate, while variations in temperature dominate the heat transport in the Fram Strait. There are significant trends over recent decades, also dominated by the Barents Sea that presently has 1 Sv higher volume transport and +1.0 ∘C warmer AW than the long‐term mean.

Ocean Heat Transport Into the Barents Sea: Distinct Controls on the Upward Trend and Interannual Variability

“…When the IAVF is maintained only inside the Arctic Ocean in the AO_vari run, the regression of SLP on the BSO transport shows a pattern with low pressure around the Svalbard and high pressure centered at the southwestern Kara Sea (Figure 5h). The wind anomaly associated with this pattern can lower the SSH on the Svalbard side through Ekman divergence (Figure 5i), thus increasing the SSH gradient and the BSO transport, consistent to previous studies on the role of local wind forcing (Ingvaldsen et al, 2002(Ingvaldsen et al, , 2004Lien et al, 2013Lien et al, , 2017Muilwijk et al, 2018;Skagseth et al, 2011).…”

Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations

“…Temperature fluctuations are important for the BSO heat transport, but it is dominated by volume fluctuations (Muilwijk et al, ; Smedsrud et al, ). The CRFs of the associated heat transports are calculated relative to 0 ° C, and overall, there is consistent CRF response among the models for the eastward volume and heat transport (Figure ).…”

“…Variability in the Barents Sea sea ice extent has been attributed to a number of processes, and variations in the ocean heat transport is key (Årthun et al, 2012;Li et al, 2017;Smedsrud et al, 2013;Venegas & Mysak, 2000;Zhang, 2015). These heat anomalies result from either increased volume transport in the Norwegian Atlantic Current, a poleward extension of the North Atlantic Current (Muilwijk et al, 2018;Smedsrud et al, 2013), or temperature anomalies that are either generated locally (Schlichtholz & Houssais, 2011) or advected in from the south (Årthun & Eldevik, 2016;Furevik, 2001;Holliday et al, 2008;Skagseth et al, 2008). This has motivated several studies that have explored the effect of wind forcing on the AW volume and heat transport.…”

Understanding Arctic Ocean Circulation: A Review of Ocean Dynamics in a Changing Climate

“…The concept and implications of polar water masses becoming closer to those typical of midlatitude oceans have also been explored on the Atlantic Ocean side of the Arctic. Mean Atlantic Water temperatures at Fram Strait and the Barents Sea Opening increased by around 1–1.5 ° C from 1980 to 2012 with long‐term trends in volume inflow estimates difficult to infer given observation limitations (Muilwijk et al, ). Recent changes in the vicinity of the Atlantic Water inflow to the Arctic Ocean, including reduced sea ice, weaker stratification, and enhanced Atlantic Water Layer heat fluxes further northeast into the Eurasian Basin, have been referred to as the Atlantification of the Arctic Ocean (Årthun et al, ; Lind et al, ; Polyakov et al, ).…”