Combined influence of oceanic and atmospheric circulations on Greenland sea ice concentration

Sourav Chatterjee,Sebastian H Mernild,Meethale Puthukkottu Subeesh,Roshin P Raj,Nuncio Murukesh,Laurent Bertino,Muthalagu Ravichandran

doi:10.5194/tc-15-1307-2021

Abstract

Abstract. The amount and spatial extent of Greenland Sea (GS) ice are primarily controlled by the sea ice export across the Fram Strait (FS) and by local seasonal sea ice formation, melting, and sea ice dynamics. In this study, using satellite passive microwave sea ice observations, atmospheric and a coupled ocean-sea ice reanalysis system, TOPAZ4, we show that both the atmospheric and oceanic circulation in the Nordic Seas (NS) act in tandem to explain the SIC variability in the south-western GS. Northerly wind anomalies associated with anomalously low sea level pressure (SLP) over the NS reduce the sea ice export in the south-western GS due to westward Ekman drift of sea ice. On the other hand, the positive wind stress curl strengthens the cyclonic Greenland Sea Gyre (GSG) circulation in the central GS. An intensified GSG circulation may result in stronger Ekman divergence of surface cold and fresh waters away from the south-western GS. Both of these processes can reduce the freshwater content and weaken the upper-ocean stratification in the south-western GS. At the same time, warm and saline Atlantic Water (AW) anomalies are recirculated from the FS region to the south-western GS by a stronger GSG circulation. Under weakly stratified conditions, enhanced vertical mixing of these subsurface AW anomalies can warm the surface waters and inhibit new sea ice formation, further reducing the SIC in the south-western GS.

Highlights

The fresh waters in the Greenland Sea (GS) play an important part for Nordic Seas overflow (Huang et al, 2020), which constitutes the lower limb of the Atlantic meridional overturning circulation (Chafik and Rossby, 2019)
Using a combination of satellite passive microwave SIC, a coupled sea ice ocean reanalysis, and atmospheric reanalysis data, we show that changes in the Greenland Sea Gyre (GSG) dynamics and resulting Atlantic Water (AW) transport in the GS can potentially influence the SIC in the southwestern GS
This indicates that a considerable amount of the SIC variability in the GS can be associated with GSG circulation

Summary

Introduction

The fresh waters in the GS play an important part for Nordic Seas overflow (Huang et al, 2020), which constitutes the lower limb of the Atlantic meridional overturning circulation (Chafik and Rossby, 2019). The freshwater content in this region is largely driven by the amount of sea ice therein (Aagaard and Carmack, 1989). Sea ice in GS is important in determining shipping routes (Instanes et al, 2005; Johannessen et al, 2007) as well as to the regional marine ecosystem due to its impact on the light availability (Grebmeier et al, 1995). Most of the sea ice in the GS is exported from the central Arctic Ocean across the Fram Strait (FS) and is largely controlled by the ice drift with the Transpolar Drift (Zamani et al, 2019). Anomalous sea ice export through the FS is associated with events like the “Great Salinity Anomaly” (Dickson et al, 1988) which can have impact on the freshwater content in the Nordic Seas. It is quite evident that the changes in sea ice export through the FS influence the GS sea ice and the freshwater availability in the Nordic Seas (Belkin et al, 1998; Dickson et al, 1988; Serreze et al, 2006)

Methods

Results

Conclusion