ABSTRACT: Ice shelves and paleoclimate at Canada’s far northern coast.

CGRG Bibliography of Canadian Geomorphology
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Abstract

High latitude regions are sentinels of global environmental change, due to polar amplification of climate warming and the sensitivity of Arctic ecosystems to environmental perturbation. Northern Ellesmere Island is home to several rare ecosystem types, including ice shelves and epishelf lakes, that are currently threatened by recent climate warming. In the early 20th century, the Ellesmere Ice Shelf (EIS) fringed much of the northern coast of Ellesmere Island. The EIS was described by the Nares Expedition (1875-76) and the Peary Expedition (1906), and since this time it has shrunk by over 90% due to melting and ice island calving. Presently, six isolated ice shelf fragments remain in the mouths fiords along this coast. Although the EIS is thought to have formed in response to climatic cooling roughly 4000 years ago, little direct evidence exists of the past dynamics of these ice shelf systems. Epishelf lakes are stratified systems where a fiord dammed by floating ice contains a layer of freshwater overlying higher density salt water. Although epishelf lakes are relatively common in the Antarctic, only one remains in the Canadian Arctic, as the ongoing deterioration of Arctic ice shelves has caused their disappearance. For example, between 1999 and 2002, the epishelf lake in Disraeli Fiord drained due to the fracturing of the Ward Hunt Ice Shelf, releasing an estimated 3.5 billion cubic metres of freshwater into the Arctic Ocean. The existence and properties of epishelf lakes depend on ice shelves, and therefore sedimentary records from fiords may yield insights into ice shelf dynamics during the Quaternary. Such records would place the recent disintegration of Arctic ice shelves in a longer-term climatic context. Here we report the results of geochemical and sedimentary pigment analyses in cores from three fiords from northern Ellesmere Island. Geochemical changes captured in the core reflect the varying influence of catchment inputs during epishelf and open periods in the fiord histories, while pigment concentrations record climate-mediated changes in their paleoproductivity. Our results suggest that these fiords and their respective ice shelves differ in their sensitivity to environmental changes, and therefore have not responded uniformly to past climates. Preliminary radiocarbon dating results suggest that our sediment sequences capture much of the Holocene. Pending paleomagnetic and further radiocarbon analyses will establish the chronology of the changes observed in the sedimentary record and improve our understanding of ice shelf dynamics and paleoclimate at Canada’s northernmost coastline.

Bibliography of Canadian Geomorphology