| Summary: | Rising ocean temperatures over the last several decades have led to an accelerated rate of sea ice decline in the northern latitudes. This study is motivated by a need to accurately model and predict sea ice dynamics in a rapidly changing climate. This study uses isotope data from the Renland ice core on the east coast of Greenland to identify the isotopic parameter deuterium excess (d-excess) as a proxy for Arctic sea ice concentration. A high d-excess signal is preserved during years with less sea ice, because a larger area of open ocean leads to increased local evaporation and kinetic fractionation of isotopes. A low d-excess signal is preserved during years with more sea ice, as a smaller area of open ocean decreases kinetic fractionation and shifts the origin of moisture towards the subtropics. Due to the strong influence that the origin of moisture has on the d-excess signal, I suggest using summer d-excess data to study changes in Arctic sea ice concentration. The greater variability seen in summer sea ice concentration leaves a stronger signal in the d-excess record and will make paleo-reconstructions more accurate. The identification of d-excess as a proxy for sea ice is the next step in constraining the spatial and temporal scale of abrupt climate change, and is vital to predicting the impact of anthropogenic climate change.
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