The role of oceanic heat flux in reducing thermodynamic ice growth in Nares Strait and promoting earlier collapse of the ice bridge

• Main Authors: Kirillov, Sergei, Dmitrenko, Igor, Babb, David G., Ehn, Jens K., Koldunov, Nikolay, Rysgaard, Søren, Jensen, David, Barber, David G.
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arctic; Arctic Ocean; Baffin Bay; Greenland; Nares; Baffin; Nares strait; Sea ice
• Online Access: https://doi.org/10.5194/os-2022-16; https://os.copernicus.org/preprints/os-2022-16/

The ice bridge in Nares Strait is a well-known phenomenon that affects the liquid and solid freshwater flux from the Arctic Ocean through the strait and controlling the downstream North Water polynya in the northern Baffin Bay. Recently, the ice bridge has been in a state of decline, either breaking up earlier or not forming at all, and thereby increasing the sea ice export out of the Arctic Ocean. The decline of the ice bridge has been ascribed to thinner and therefore weaker ice from the Arctic Ocean entering Nares Strait, however local forcing also affects the state of the ice bridge and thereby influences when it breaks up. Using a variety of remotely sensed data we examine the spatial patterns of sea ice thickness within the ice bridge; highlighting the presence of negative ice thickness anomalies on both the eastern and western sides of the Strait, and identifying a recurrent sensible heat polynya that forms within the ice bridge near Cape Jackson in northwestern Greenland. Using the sea ice-ocean model FESOM2, we then attribute these ice thickness anomalies to upwelling of warm modified water of Atlantic origin (mAW) that reduces thermodynamic ice growth throughout winter. The consequently weaker and thinner areas within the ice bridge promote instability and the earlier break up. This work provides new insight into the Nares Strait ice bridge, and highlights that a combination of thinner ice and warmer mAW entering the Strait is contributing to its decline.