Abstract
ABSTRACTWe assess ice loss and velocity changes between 1985 and 2014 of three tidewater and five-land terminating glaciers in Godthåbsfjord (Nuup Kangerlua), Greenland. Glacier thinning accounted for 43.8 ± 0.2 km3 of ice loss, equivalent to 0.10 mm eustatic sea-level rise. An additional 3.5 ± 0.3 km3 was lost to the calving retreats of Kangiata Nunaata Sermia (KNS) and Narsap Sermia (NS), two tidewater glaciers that exhibited asynchronous behavior over the study period. KNS has retreated 22 km from its Little Ice Age (LIA) maximum (1761 AD), of which 0.8 km since 1985. KNS has stabilized in shallow water, but seasonally advects a 2 km long floating tongue. In contrast, NS began retreating from its LIA moraine in 2004–06 (0.6 km), re-stabilized, then retreated 3.3 km during 2010–14 into an over-deepened basin. Velocities at KNS ranged 5–6 km a−1, while at NS they increased from 1.5 to 5.5 km a−1 between 2004 and 2014. We present comprehensive analyses of glacier thinning, runoff, surface mass balance, ocean conditions, submarine melting, bed topography, ice mélange and conclude that the 2010–14 NS retreat was triggered by a combination of factors but primarily by an increase in submarine melting.
Highlights
Glaciers along the margin of the Greenland ice sheet (GrIS) have been thinning and retreating over the past several decades (Warren, 1991; Warren and Glasser, 1992; Moon and Joughin, 2008; Leclercq and others, 2012) with tidewater outlet glaciers accounting for much of the ice loss: up to 58% before 2005 (e.g. Rignot and Kanagaratnam, 2006; Van den Broeke and others, 2009; Rignot and others, 2011; Shepherd and others, 2012) and 32% between 2009 and 2012 (Enderlin and others, 2014)
The net change in summer position between 1985 and 2015 (0.8 km) represents ∼3.6% of the ∼22 km retreat from its 1761 AD Little Ice Age (LIA) maximum (Lea and others, 2014a)
Land-terminating glaciers all showed negative balance to varying degrees (Fig. 11a). These results qualitatively correspond with our geodetic assessment of ice loss for the land
Summary
Glaciers along the margin of the Greenland ice sheet (GrIS) have been thinning and retreating over the past several decades (Warren, 1991; Warren and Glasser, 1992; Moon and Joughin, 2008; Leclercq and others, 2012) with tidewater outlet glaciers accounting for much of the ice loss: up to 58% before 2005 (e.g. Rignot and Kanagaratnam, 2006; Van den Broeke and others, 2009; Rignot and others, 2011; Shepherd and others, 2012) and 32% between 2009 and 2012 (Enderlin and others, 2014). All three tidewater glaciers have experienced thinning and acceleration during the past two decades, similar to tidewater outlet glaciers elsewhere along the GrIS margin (Rignot and Kanagaratnam, 2006; Joughin and others, 2010a).
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