Role of Atlantification in Enhanced Primary Productivity in the Barents Sea

Recent changes in the Arctic sea-ice are strongly influenced by the recent increase in heat transport from vigorous Atlantic inflows, so-called Atlantification. This Atlantification can induce physical and ecological changes near the Atlantic gateway. Here, we used the observational data sets and 26 Earth system models to estimate Atlantic water intrusion, and firstly suggest the impact of Atlantification on marine productivity in the Barents Sea in a warming climate, especially on boreal spring. In a warming climate, the heat transport across the Barents Sea Opening (BSO) is projected to be enhanced (45.5 +/- 34.9 TW) by the end of the 21st century compared to the present climate. This poleward intrusion of the Atlantic water is likely to increase productivity with the largest increase in spring (70%). In a warming climate, the productivity is enhanced by Atlantification-induced changes in physical states-ocean temperature, circulations, stratification, and sea-ice. Based on inter-model analyses, we estimated that the Atlantification can explain approximately 26% of the productivity changes in the Barents Sea. Thus, Atlantification is critical for future changes in biological productivity and physical states over the Arctic Ocean. Human-induced greenhouse gases are causing the sea-ice in the Arctic Ocean to decrease. This is making the edges of the sea-ice retreat poleward to the central Arctic. The Atlantic water, which is warm, salty, and nutrient-rich, is also expanding northwards. This is causing the Arctic water to become more like Atlantic water, which is called "Atlantification." Atlantification-induced physical manifestations and their future changes have been relatively well understood, while influence of the marine productivity still has large uncertainties. In this study, we analyzed the 26 state-of-the-art Earth system models (ESMs) and estimated the future changes caused by the Atlantification, and related productivity changes based on diverse responses of model projections in the Barents Sea where the largest productivity change exists over the Arctic Ocean. We find that the Atlantification-induced changes in temperature, sea-ice, and vertical mixing, can enhance the level of productivity in the Barents Sea, especially in boreal spring. Our results suggest that understanding the interactions between the Atlantic water and Arctic systems such as ocean, cryosphere, and biology is critical to projecting future Arctic productivity. The extents of Atlantic water expand to the central Arctic basin due to increased heat transport through the Atlantic gateways in a warming climateThe intensified Atlantification drives the enhancement of spring productivity in the Barents SeaNotable divergence in physical manifestations of Atlantification among CMIP models engenders significant challenges in projecting future Arctic productivity