Application of “annual” moraines to assess recent patterns and rates of ice-marginal retreat at Skálafellsjökull, SE Iceland

Abstract

Iceland is situated in a climatically sensitive area close to both atmospheric and oceanic polar fronts, thus representing an important location for understanding North Atlantic climatic change. Icelandic glaciers are particularly sensitive to climatic fluctuations on annual to decadal timescales, and have exhibited accelerating rates of ice-marginal retreat and mass loss during the past decade. Understanding these current rapid glacier fluctuations is crucial to placing current atmospheric warming and associated glacier retreat in a broader context.

This study uses the characteristics of recessional (“annual”) moraines and complementary climate data to examine patterns, rates and drivers of ice-marginal retreat that has occurred at Skálafellsjökull, SE Iceland since the 1930s. High-resolution glacial geomorphological mapping reveals suites of minor moraines across the glacier foreland, with the features displaying distinctive sawtooth planform geometries. Chronological investigations of the Skálafellsjökull moraines, which integrate remote sensing observations and lichenometry, indicate that minor moraines on the northern and central parts of the glacier foreland formed on an annual basis. Sedimentological investigations reveal that these annual moraines form through a range of ice-marginal processes, with push/squeeze mechanisms being dominate. The geomorphological, chronological and sedimentological data therefore indicate these moraines represent successive annual ice-frontal positions. Thus, these annual moraines provide a framework for exploring patterns, rates and drivers of ice-marginal retreat at Skálafellsjökull.

Annual ice-margin retreat rates (IMRRs), equivalent to annual moraine spacing, indicate prominent periods of glacier recession at Skálafellsjökull are coincident with those at other Icelandic outlet glaciers, as well as those identified at Greenlandic outlet glaciers. Analysis of IMRRs and climate data suggests summer air temperature, sea surface temperature and North Atlantic Oscillation have an influence on IMRRs at Skálafellsjökull, with the glacier appearing to be most sensitive to summer air temperature. Based on this analysis, it is hypothesised that sea surface temperature may drive air temperature changes in the North Atlantic region, which in turn forces IMRRs. The increase in SST over recent decades may link to atmospheric-driven variations in North Atlantic subpolar gyre dynamics. Further research on glacier change in the North Atlantic region, and the controls thereon, is nonetheless required to test this hypothesis.