Abstract
The retreat and acceleration of marine-terminating outlet glaciers in Greenland over the past two decades has been widely attributed to climate change. Here we present a comprehensive annual record of glacier terminus positions in northwest and central-west Greenland and compare it against local and regional climatology to assess the regional sensitivity of glacier termini to different climatic factors. This record is derived from optical and radar satellite imagery and spans 87 marine-terminating outlet glaciers from 1972 through 2021. We find that in this region, most glaciers have retreated over the observation period, and widespread regional retreat accelerated around 1996. The acceleration of glacier retreat coincides with the timing of sharp shifts in ocean surface temperatures, duration of sea-ice season, ice-sheet surface mass balance, and meltwater and runoff production. Our findings suggest that a variety of processes – such as ocean-interface melting, mélange presence and rigidity, and hydrofracture-induced calving – contribute to, but do not conclusively dominate, the observed regional retreat.
Highlights
The Greenland Ice Sheet has lost significant mass over the last few decades (Enderlin et al, 2014; Shepherd et al, 2020) as many of its glaciers have retreated (Hill et al, 2017; Howat and Eddy, 2011; Moon and Joughin, 2008; Murray et al, 2015; 20 King et al, 2020), and ice flow has accelerated (Moon et al, 2012; Rignot and Kanagaratnam, 2006; Joughin et al, 2010)
Howat and Eddy (2011) found that between 2000 and 2010, nearly 100% of glaciers in northwest Greenland retreated; we considered a larger set of glaciers, we found that 85% of our glaciers retreated and 15% were stable over the same time period
As evidence of this effect, we note the strong response to seasonal perturbations on three of Greenland’s deepest outlet glaciers (Jakobshavn, Kangerlussuaq, and Helheim), which is large compared to the degree of melting at the terminus (Kehrl et al, 2017; Joughin et al, 2020)
Summary
The Greenland Ice Sheet has lost significant mass over the last few decades (Enderlin et al, 2014; Shepherd et al, 2020) as many of its glaciers have retreated (Hill et al, 2017; Howat and Eddy, 2011; Moon and Joughin, 2008; Murray et al, 2015; 20 King et al, 2020), and ice flow has accelerated (Moon et al, 2012; Rignot and Kanagaratnam, 2006; Joughin et al, 2010). Recent Greenland ice loss has contributed to rates at times approaching 1 mm a-1 of global sea-level rise (Shepherd et al, 2020), with the contribution from northwest and central-west Greenland combined representing nearly half of the cumulative contribution from Greenland to sea-level rise since 1972 (Mouginot et al, 2019). Surface mass balance has dominated Greenland’s mass loss in the past two decades, in northwest and central-west Greenland over half of the mass loss 25 is currently due to ice discharge (Mouginot et al, 2019), which has accelerated since 2000 in this region (King et al, 2020).
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