Abstract:

 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.