An early Holocene deglaciation chronology for Sam Ford Fiord, Baffin Island, Arctic Canada: An analog for presently-retreating Greenland outlet glaciers
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The Earth's ice sheets hold the potential to greatly affect changes in sea level as climate continues to warm. To better understand how these continental ice sheets may react in the future, we can look at the response of former ice sheets to periods of rapid warming. The Laurentide Ice Sheet experienced a period of significant warming during the early Holocene. On Baffin Island in Arctic Canada, ice drained from the northeastern margin of the Laurentide Ice Sheet via large outlet glaciers that resided within the fiords that dissect the landscape there. However, the pattern and timing of post-Last Glacial Maximum retreat of the Laurentide Ice Sheet from its terminal position along the northeastern coast of Baffin Island is largely unresolved. Cosmogenic exposure dating has afforded glacial geologists the opportunity to easily and accurately develop deglaciation chronologies for formerly glaciated regions where radiocarbon datable material is sparse or non-existent. I employ 10 Be surface exposure dating and radiocarbon dating to reconstruct the early Holocene retreat chronology for Sam Ford Fiord, NE Baffin Island, Arctic Canada. The mouth of Sam Ford Fiord became ice-free ∼10.3 ka. Subsequently, the outlet glacier retreated rapidly through the mid-fiord between ∼10 and ∼9.5 ka, pulling back nearly 100 km during this time. Between ∼9.5 and ∼7 ka, the outlet glacier fluctuated within the inner fiord, building multiple sets of lateral moraines while repeatedly retreating and readvancing during the Holocene Thermal Maximum, the warmest period of the last 120 ka. Radiocarbon dates from a prominent ice-contact raised marine delta suggest that one of these readvances may have been in response to the 8.2 ka cooling event. Because of the complexity of the moraine record and the lack of any other documented cold triggers, however, it is proposed that fiord geometry and tidewater glacier dynamics controlled the position of the ice margin and triggered fluctuations within inner Sam Ford Fiord during the early Holocene. Tidewater glaciers often respond dynamically to changes in water depth at the glacier terminus, retreating rapidly in deep water, and stabilizing within shallower waters. The pattern of retreat within Sam Ford Fiord documented here agrees, with the glacier retreating catastrophically through the deep mid-fiord waters, and then stabilizing and remaining within the shallow inner fiord waters for nearly 2500 years. The volatile and unpredictable nature of the retreat of Sam Ford Fiord's outlet glacier during the early Holocene may provide some insight into how the outlet glaciers of the Greenland Ice Sheet will respond to continued warming in the future.