Exceptional 20th century glaciological regime of a major SE Greenland outlet glacier

Camilla S Andresen,Vincent Klein,Fanny Kaczmar,Mads Faurschou Knudsen,Laurence M Dyke,David Wangner,Marie-Alexandrine Sicre,Martin W Miles,Ulla Kokfelt

doi:10.1038/s41598-017-13246-x

Abstract

The early 2000s accelerated ice-mass loss from large outlet glaciers in W and SE Greenland has been linked to warming of the subpolar North Atlantic. To investigate the uniqueness of this event, we extend the record of glacier and ocean changes back 1700 years by analyzing a sediment core from Sermilik Fjord near Helheim Glacier in SE Greenland. We show that multidecadal to centennial increases in alkenone-inferred Atlantic Water SSTs on the shelf occurred at times of reduced solar activity during the Little Ice Age, when the subpolar gyre weakened and shifted westward promoted by atmospheric blocking events. Helheim Glacier responded to many of these episodes with increased calving, but despite earlier multidecadal warming episodes matching the 20th century high SSTs in magnitude, the glacier behaved differently during the 20th century. We suggest the presence of a floating ice tongue since at least 300 AD lasting until 1900 AD followed by elevated 20th century glacier calving due to the loss of the tongue. We attribute this regime shift to 20th century unprecedented low sea-ice occurrence in the East Greenland Current and conclude that properties of this current are important for the stability of the present ice tongues in NE Greenland.

Highlights

In the last two decades there has been a rapid increase in the loss of ice from the Greenland Ice Sheet[1]
Climatic modes may have influenced glacier calving through modulation of warm subsurface waters on the SE Greenland shelf and inside the fjord and that, episodes of increased cold polar waters occurrence may have potentially stabilised the glacier termini
Almost nothing is known about the behaviour of Helheim Glacier before the 20th century and how on-going climate changes will affect the dynamics of outlet glaciers

Summary

Greenland outlet glacier

The link between climatic changes and outlet glacier variability during the past century has been demonstrated by a reconstruction of Helheim Glacier calving based on the combination of three sediment cores from Sermilik Fjord[14] This high-resolution record (up to 1 year) documents several episodes of increased iceberg calving of which the youngest marked episode occurred between 2000 and 2005. Our new record shows that the high 20th century SSTs were matched during several previous multidecadal warm episodes during the DACP and LIA, yet the IRD record demonstrates that Helheim Glacier behaved differently in the 20th century We attribute this finding to the presence of a relatively marked floating tongue at Helheim Glacier at least since the DACP, lasting until the abrupt end of the LIA in the early 20th century and suggest that the glaciological regime shift was triggered by unprecedented low sea-ice concentrations in the EGC during the 20th century.

Material and Methods

Author Contributions

Findings

Additional Information