The effects of atmospheric and oceanic conditions on the stability of ice bridges

Stelma, Sigourney Anne
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University of Delaware
Ice bridges are arch-like ice structures that form in narrow passages and straits. These bridges play largely important roles in the circulation of Arctic sea ice. When an ice bridge is present in a strait, there is typically a stoppage of sea ice flow, and there generally little ice flow downstream from the bridge. Nares Strait, located between Ellesmere Island and Greenland, allows for Arctic sea ice to be exported into the Atlantic Ocean. Ice bridges typically form in Nares Strait, which causes a stoppage of this export. This stoppage allows for Arctic sea ice to grow thicker, which is important for our current climate. Building on studies that examined the formation of ice bridges, this study aims to model and analyze the destruction of ice bridges. Using CICE: The Los Alamos Sea Ice Model, ice bridges are modeled in an idealized strait that is geographically and dimensionally similar to Nares Strait. The bridges are allowed to strengthen for 7 days past their initial formation. Then various atmospheric and oceanic parameters are changed, to examine their effect on the stable ice bridges. All parameter changes are applied over the entire domain and are constant in time. Extreme temperatures are used to study the effect of temperature. Then various amounts of longwave and shortwave radiation are tested independently, combined with temperature and combined with each other and temperature. We found that air temperature alone isn't the driving mechanism in bridge disintegration. As for radiative forcing, long- wave radiation proves to have a stronger effect than shortwave radiation. In fact, when air temperature, longwave radiation and shortwave radiation are combined, longwave radiation is the most dominant factor in disintegrating the bridges, followed by air temperature. Wind and currents are also tested. A seasonal progression, from winter to summer, is also applied to stable ice bridges of different initial thicknesses. All bridges studied under the seasonal progression were destroyed within the three season time constraint.