Shrubs shed light on 20th century Greenland ice sheet melting

Abstract

The Greenland Ice Sheet (GrIS) is a key element of the global climate system and thus knowledge about its melting in the past is desirable. However, GrIS-melt records only date back until 1979 and climate data based reconstructions covering the 20th century differ with respect to absolute values. To extend our knowledge about the Greenland Ice Sheet we examined the potential of shrub ring-widths and wood-anatomy as proxies for GrIS-melt. We found significant correlations between shrub cell-wall thickness and regional melt derived from passive microwave satellite brightness for 7% of the total GrIS area. A respective transfer function calibrated over the period 1979 to 2007 successfully passed model calibration-verification tests and explained 42% of GrIS-melt variability. Consequently, the first GrIS-melt reconstruction based on shrub wood-anatomy covering the period 1909 to 2012 is presented and compared against two temperature-based reconstructions. For the period prior to 1930 the new reconstruction contrasts with existing literature but generally confirms that most recent record melt rates are amongst the highest since the early 20th century. We discuss the sensitivity of shrubs to several influencing factors besides summer temperature as possible reason for the observed differences and highlight the potential of using shrubs as multi-parameter proxies within a network to increase our knowledge about 20th century Greenland Ice Sheet dynamics. © 2017 Collegium Boreas. Published by John Wiley & Sons Ltd