On the Physical Settings of Ice Bridge Formation in Nares Strait

• Published in: Journal of geophysical research. Oceans Vol. 126; no. 8
• Main Authors: Kirillov, S., Babb, D. G., Komarov, A. S., Dmitrenko, I., Ehn, J. K., Worden, E., Candlish, L., Rysgaard, S., Barber, D. G.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-08-2021
• Subjects: Air temperature; Alignment; arch; Arctic ice; Bridge failure; Bridges; consolidation; Environmental conditions; formation; Freeboard; Freshwater; Freshwater ice; Geophysics; ice bridge; Ice cover; Ice formation; Ice thickness; Imagery; Inland water environment; landfast ice; Low wind speeds; Nares Strait; Neap tides; Oceans; Polynyas; Satellite data; Satellite imagery; Sea ice; Spaceborne remote sensing; Stability; Straits; Thickness; Tidal amplitude; Transport; Wind speed; Winds; Winter; Baffin Bay; Nares Strait
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2021JC017331

The ice bridge that forms seasonally across Nares Strait impedes the southward transport of sea ice from the Lincoln Sea to Baffin Bay and contributes to the maintenance of the North Water Polynya. Previous studies have quantified how the bridge affects ice export and highlighted a long term decline in the duration of the bridge; however, the specific mechanism by which the bridge forms has remained unstudied. In this study we first used a mix of satellite imagery to refine the timing of formation for the 16 bridges that formed between 2000 and 2021, and subsequently examine the atmospheric and oceanic forcing around these events. It was found that, on average, the ice bridges formed 3 days earlier than reported in previous studies. In general, the bridges formed during periods of cold air temperatures (less than −15°C), around neap tide, and during a cessation or even reversal in the prevailing north‐northeasterly winds. Specific quantitative criteria of the environmental conditions favorable for bridge formation are presented and discussed. It was shown, however, that the alignment of these conditions does not always lead to the formation of a bridge, indicating that other factors such as ice thickness and landfast ice stability may limit the formation. A comparison of ice freeboard in Kane Basin between winter 2020 (bridge) and 2019 (no bridge) revealed that the ice pack was thinner in 2019, which may have precluded the formation of the bridge. This is critical as the Arctic ice pack continues to thin.
Plain Language Summary
Nares Strait is located between Ellesmere Island and Greenland, and is an important pathway for water and ice flowing from the Arctic Ocean into Baffin Bay. Historically, sea ice export was halted during winter by the consolidation of ice into an ice bridge within the strait. The ice bridge has traditionally been used as transportation route by Inuit and contributes to the formation of the extensive polynya further south. There has been a trend toward later formation and earlier collapse of the bridge, but the specific conditions under which the bridge forms has remained unstudied. We use several types of satellite data to narrow the dates of formations between 2000 and 2021. Then, we examined the atmospheric and oceanic forcing around these events. We found that the bridges formed during cold periods with low tidal amplitude and low wind speeds. However, the alignment of these conditions does not always lead to the formation of an ice bridge, indicating that other factors such as ice thickness and landfast ice stability may limit the bridge formation. Our results will help us understand how ice bridges might change in future, affecting the flow of ice and freshwater into the western North Atlantic Ocean.
Key Points
The timings of ice bridge formation in southern Nares Strait between 2000 and 2020 are refined to an uncertainty of ±12 h
Bridges formed during periods of low air temperatures and a cessation or reversal in the prevailing northeasterly winds around neap tide
However, other factors such as ice thickness and ice strength are also critical for bridge formation