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

Abstract

Major changes have occurred in the Arctic Ocean during 2000–2019, including the unprecedented spin-up of the Beaufort Gyre and the emergence of Arctic Atlantification in the eastern Eurasian Basin. We explored the main drivers for these changes by synthesizing numerical simulations and observations in this paper. The Arctic atmospheric circulation was unusual in some years in this period, with strongly negative wind curl over the Canada Basin. However, the wind-driven spin-up of the Beaufort Gyre would have been much weaker had it not been for Arctic sea ice decline. The sea ice decline not only fed the ocean with meltwater, but also made other freshwater components more available to the Beaufort Gyre through mediating the ocean surface stress. This dynamical effect of shifting surface freshwater from the Eurasian Basin towards the Amerasian Basin also resulted in the Arctic Atlantification in the eastern Eurasian Basin, which is characterized by halocline salinification and the uplift of the boundary between the halocline and the Atlantic Water layer. Contemporarily, the sea ice decline caused a strong warming trend in the Atlantic Water layer. The Empirical Orthogonal Function (EOF) analysis of Arctic annual sea surface height for this period reveals that the first two modes of the upper ocean circulation have active centers associated with the Arctic Oscillation and Beaufort High variability, respectively. In the presence of sea ice decline the first two EOFs can better distinguish the ocean variability driven by the two atmospheric circulation modes. Therefore, the major changes in the Arctic Ocean in the past two decades are indicators of climate change as is the sea ice retreat. Our synthesis could help assess how the Arctic Ocean might change in future warming climate.

Future Arctic Climate Change in CMIP6 Strikingly Intensified by NEMO‐Family Climate Models

“…However, with the rapid increase in Arctic temperatures and the melting of sea ice, the Arctic Ocean stratification is changing. The reduction in sea ice cover has promoted stronger vertical mixing in the upper ocean (Rainville & Woodgate, 2009; Tsamados et al., 2014) and weakened the halocline stratification in the Arctic Eurasian Basin (Polyakov, Rippeth, et al., 2020; Wang & Danilov, 2022). These ocean changes could contribute to the ventilation of the Atlantic Water layer and enhance sea ice basal melting (Polyakov et al., 2017; Polyakov, Alkire, et al., 2020).…”

Variability of Eddy Kinetic Energy in the Eurasian Basin of the Arctic Ocean Inferred From a Model Simulation at 1‐km Resolution

“…The presence of eddy effects on sea ice melting in the Eurasian Basin during winter, as revealed in this study, is a cause for concern, especially when considered alongside previous findings of eddy‐induced sea ice melting in the MIZ of the Amerasian Basin during summer time (Manucharyan & Thompson, 2022). The ongoing “Atlantification” of the Eurasian Basin (Polyakov et al., 2017; Wang & Danilov, 2022), and the projected warming of the Atlantic Water layer of the Arctic Ocean at a rate faster than the global ocean mean rate in the future (Shu et al., 2022), together with elevated eddy activity, will likely increase the ocean‐ice heat flux considerably. This will further enhance basal melting and hence retreat of sea ice in a warmer world.…”

“…The model simulation was carried out with the unstructured‐grid global Finite volumE Sea ice Ocean Model version 2 (FESOM2, Danilov et al., 2017), allowing the use of variable resolution without the need for nesting. The model is similar to its predecessor (FESOM1.4, Wang et al., 2014), which has been used for a number of Arctic studies with around 4.5 km horizontal resolution (e.g., Wang & Danilov, 2022; Wang et al., 2018, 2019, 2021; Wekerle et al., 2017). The sea ice component of the model (Finite‐Element Sea Ice Model, version 2) with an Elastic‐Viscous‐Plastic (EVP) rheology runs on the same unstructured mesh (Danilov et al., 2015).…”

Arctic Ocean simulations in the CMIP6 Ocean Model Intercomparison Project (OMIP)

“…The general circulation in the Arctic Ocean is the superposition of Atlantic Water flowing into and around the Arctic Basin and two main wind-driven circulation features of the interior strati- fied Arctic Ocean: the Transpolar Drift Stream and the Beaufort Gyre (Fig. 1) (Timmermans and Marshall, 2020;Wang and Danilov, 2022). Warm and saline Atlantic Water enters the Arctic Ocean with two branches.…”

“…The Arctic Ocean receives large amounts of freshwater from river runoff, oceanic freshwater flux through the Bering Strait, and net precipitation, and it releases freshwater through the Davis Strait and Fram Strait (Serreze et al, 2006;Dickson et al, 2007;Ilicak et al, 2016). Observations show that liquid freshwater stored in the Arctic Ocean has increased since the mid-1990s and stabilized in the 2010s with an unprecedented amount of freshwater accumulated in the Amerasian Basin (Rabe et al, 2014;Polyakov et al, 2013;Wang et al, 2019b;Wang and Danilov, 2022;Solomon et al, 2021).…”