Little Ice Age climate in South Greenland inferred from alpine glacier reconstructions

Abstract:

Alpine glaciers are very sensitive to small changes in climate, and therefore reconstructing past fluctuations of alpine glaciers informs our understanding of global and regional paleoclimate histories. The Little Ice Age was a multi-century period of colder conditions around much of the North Atlantic region that ended circa 1850-1900 AD. In Greenland, there are limited records of Little Ice Age alpine glacier extent and considerable unknowns about the magnitude, timing, and causes of cooling. Here, we use the location of historical terminal moraines and trimlines to constrain Little Ice Age glacier extents for 50 glaciers in South Greenland, then we use geospatial and numeric methods to reconstruct the corresponding past glacier surfaces. We estimate the change in equilibrium line altitude for each Little Ice Age paleoglacier compared with present day. Our results provide insights into the temperature and precipitation anomalies during the coldest part of the Little Ice Age in the climatically heterogeneous region of southernmost Greenland. The average change in equilibrium line altitude for the 50 glaciers studied was 90 ± 45 m, which corresponds with a Little Ice Age temperature anomaly of 0.7-0.9 ⁰C if it is assumed that there has not been a change in mean annual accumulated precipitation. We also reconstruct temperature anomalies if it is assumed that the Little Ice Age was substantially wetter or drier than present day in South Greenland. This work demonstrates the use of relatively novel geospatial methods to reconstruct regional paleoclimate from remote-sensed alpine glacier geomorphology.