Holocene ice margin fluctuations of the Greenland Ice Sheet in the Disko Bugt region, West Greenland
Kelley, Samuel E.
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The current response of the Greenland Ice Sheet (GrIS) margin to climate change is spatially and temporally variable. Understanding the mechanisms that control this variability is crucial for accurate predictions of how the GrIS will change in the future. One factor that appears to play a role in driving the varying response exhibited along the margin of the GrIS is the ice margin setting (marine-terminating or land-terminating). Recent research has demonstrated that basal melting of marine-terminating glaciers may increase their vulnerability to climatic perturbations, while their land-terminating counterparts may lag in their reaction similar climatic changes. While these trends are illustrated in historic and modern records, longer temporal records are needed to place these observations in context. Here, I present a chronology of GrIS fluctuations within the Disko Bugt region of West Greenland. This record spans the Holocene, and is constrained by 10Be and radiocarbon ages. Through building this chronology, I reconstruct the pattern and timing of Holocene ice margin fluctuations and evaluate the response of differing ice margin types (marine-based or land-based) to regional climate forcing. From my chronology it is apparent that, on millennial timescales early Holocene ice margin retreat rates were synchronous within Disko Bugt. This pattern extends along the western margin of the GrIS, with all the sections of the ice margin examined displaying similar retreat rates despite dissimilar marginal settings. This is strikingly different than modern trends, where marine-based outlet glaciers exhibit significantly higher retreat rates than their land-based counterparts. The record of ice margin reaction to recent warming demonstrates a distinct pattern of asynchrony. In my late Holocene records, marine-based glaciers initiate retreat much sooner than land-based sectors of the ice margin. I believe this feature demonstrates a relationship between ice margin type and response time. I propose that in West Greenland faster glaciers maintain a closer equilibrium with changing climate than slower flowing glaciers. In total, the historic pattern of relative stability of land-based sectors of the GrIS is in contrast with the longer records of Holocene ice margin fluctuation. Additionally, a relationship between ice margin type and response time suggests that land-based sectors of the ice margin lag in their reaction to climate forcing on decadal scales. This indicates that historically stable sectors of the ice margin may be expected to undergo significant future retreat, as a larger percentage of the GrIS margin begins to react to 20th century warming.