FORCING A GLACIER FLOW MODEL USING MASS BALANCE RECONSTRUCTIONS BASED ON BLUE INTENSITY TREE-RING RECORDS: EXPLORING THE MILLENNIUM-LONG ADVANCE OF COLUMBIA GLACIER, SOUTH-CENTRAL ALASKA

Tidewater glaciers are major contributors to sea level rise, however, their flux to the world’s oceans now and in the future is not well constrained. In part, this is because ice fluctuations are often decoupled from climate. Thus, a better understanding of glacier behavior necessitates high-resolution climate data, which may better inform projections of glacier and sea level change. Columbia Glacier, one of the largest and most rapidly changing tidewater glaciers in Alaska, has retreated more than 20 km over the past 30 years. Previous work has reconstructed the advance of the ice since ~1000 CE based on over 300 tree-ring dates on overridden trees. In the current study, we add a millennium-long reconstruction of summer temperature variability developed using a new proxy record based on blue intensity tree-ring records (BI). We combine this new summer temperature record with a one-dimensional ice flow model to test the relative importance of climate on Columbia Glacier’s advance behavior. Using physical parameterizations from previous work, the model simulates advance from ice-free conditions by updating glacier height along the central flowline. Each year of advance is influenced by the reconstructed mass balance for that year. Historical glacier lengths are constrained by the detailed tree-ring dates from along fjord margins. While previous work incorporated a mass balance forcing proportional to tree-ring widths, the new BI values, which serve as a proxy for summer temperature, display a stronger correlation with mass balance than previously investigated ring width. Results show the advance history of Columbia Glacier as forced by the newly reconstructed mass balance record, enhancing our understanding of the glacier’s sensitivity to past and future climate change within the larger context of tidewater glacier dynamics. Future model experiments calibrated with geologic data derived from the tree-ring record may help constrain the non-climatic controls on tidewater glacier behavior.