Rapid response of Helheim Glacier in Greenland to climate variability over the past century

Abstract

The forcings behind the rapid increase in mass loss from the Greenland Ice Sheet in the early 2000s (ref. 1) are still debated. It is unclear whether the mass loss will continue in the near future and, if so, at what rate. These uncertainties are a consequence of our limited understanding of mechanisms regulating ice-sheet variability and the response of fast-flowing outlet glaciers to climate variability. In southeast Greenland, Helheim Glacier, one of the regions largest glaciers, thinned, accelerated and retreated during the period 2003-2005 (ref. 4) and although it has since slowed down and readvanced 9 , it has still not returned to its pre-acceleration flow rates. It has been suggested that warming 8,10 and/or inflow variability 11,12 of the nearby subsurface ocean currents triggered the acceleration, but to establish a causal relationship between glacier and climate variability, long-term records are needed. Here we present three high-resolution (1-3 years per sample) sedimentary records from Sermilik Fjord ( Fig. 1 and Supplementary Information) that capture the 2001-2005 episode of mass loss, and use them to reconstruct the calving variability of Helheim Glacier over the past 120 years. Next, this record is compared with records of climate indices.

Combining damage and fracture mechanics to model calving

“…As stated by Andresen et al (2011), Helheim Glacier's front position remained within a range of 8 km over the last 80 years. During this period, the glacier underwent several advances and retreats.…”

“…Over the last century, Helheim Glacier has probably undergone several advance and retreat cycles (Andresen et al, 2011). Observations of sand deposits showed that variations in the front did not exceed 10 km.…”

Ice flux evolution in fast flowing areas of the Greenland ice sheet over the 20th and 21st centuries

“…Joughin and others, 2008b;Nettles and others, 2008), making this glacier one of the most prolific iceberg exporters in Greenland (e.g. Andresen and others, 2011). Furthermore, Andresen and others (2011) show that the HLH glacier responds to atmosphereocean variability on short timescales (3-10 years).…”

“…Andresen and others, 2011). Furthermore, Andresen and others (2011) show that the HLH glacier responds to atmosphereocean variability on short timescales (3-10 years). In our simulations, small calving events at the front of both glaciers are simulated at a very high frequency (1-2 years) leading to a strong interannual variability in their ice flux evolution at the downstream sections during the 20th and 21st centuries (Figs 5c, d).…”

“…Joughin and others, 2008b;Nettles and others, 2008;Andresen and others, 2011). Currently, the HLH glacier front is characterized by many calving events (e.g.…”