Observed sediment and solute transport from the Kangerlussuaq sector of the Greenland Ice Sheet (2006–2016)

Abstract

New measurements of Watson River sediment and solute concentrations and an extended river discharge record improved by acoustic Doppler current profiler (ADCP) measurements are used to calculate the total sediment and solute transport from a large ice-sheet sector in southern west Greenland. For the 2006-2016 period, the mean annual sediment and solute transport was 17.5 ± 7.2 × 10 6 t and 85 ± 30 × 10 3 t, respectively (standard deviation given). The highest annual transport occurred in 2010, attaining values of 29.6 × 10 6 t and 138 × 10 3 t, respectively. The corresponding annual average values of specific transport are 1.39 × 10 3 t km −2 a −1 for sediment and 6.7 t km −2 a −1 for solutes from the approximately 12,600 km 2 (95% ice covered) catchment, yielding an area-average erosion rate of 0.5 mm a −1. The specific transport is likely several times higher under the ice sheet near the margin where all meltwater passes than it is in the interior where the ice sheet is frozen to the bed. We conclude that the Greenland Ice Sheet is a large supplier of sediment and solutes to the surrounding fjords and seas. We find that the proglacial area can be a net source of sediments during high floods and we confirm that an increased amount of meltwater-transported sediments can explain the expansion of deltas around Greenland, contradictory to delta erosion observed elsewhere in the Arctic in recent years. ARTICLE HISTORY

Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

“…This indicates the need for a careful and consistent approach to defining the effective drainage basin area in glacial erosion studies for major outlet glaciers. Modern glacial erosion rates have also been provided for the well-studied Kangerlussuaq area in central west Greenland, by measuring annual sediment loads (suspended and in solution) in proglacial rivers beyond land-terminating glaciers (Cowton et al, 2012;Hawkings et al, 2015;Hasholt et al, 2018) and dividing by the catchment area. Although individual study years have returned rates as high as 4.5 mm a −1 , for the decade 2006-2016 the average rate was 0.5 mm a −1 (Hasholt et al, 2018).…”

“…Modern glacial erosion rates have also been provided for the well-studied Kangerlussuaq area in central west Greenland, by measuring annual sediment loads (suspended and in solution) in proglacial rivers beyond land-terminating glaciers (Cowton et al, 2012;Hawkings et al, 2015;Hasholt et al, 2018) and dividing by the catchment area. Although individual study years have returned rates as high as 4.5 mm a −1 , for the decade 2006-2016 the average rate was 0.5 mm a −1 (Hasholt et al, 2018). These studies used a consistent approach to defining the catchment area based on the ablation area for the Kangerlussuaq drainage basin and modelled hydrological catchment, which we deem as comparable to the approach taken here (i.e.…”

“…This has implications for marine biogeochemical cycles (e.g. Hawkings et al, 2015) and ultimately organic carbon sequestration in fjord sediments, which are a known hotspot for carbon burial (Smith et al, 2015). Yet we have very few estimates of glacial erosion or sediment fluxes for either the present-day GrIS or for past configurations of the ice sheet (Hallet et al, 1996;Overeem et al, 2017).…”

Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, NW Greenland

“…Modern glacial erosion rates have also been provided for the well-studied Kangerlussuaq area in central West Greenland, by measuring annual sediment loads (suspended and in solution) in proglacial rivers beyond land-terminating glaciers (Cowton et al, 2012;Hawkings et al, 2015;Hasholt et al, 2018) and dividing by the catchment area. Although individual study years have returned rates as high as 4.5 mm a -1 , for the decade 2006-2016 the average rate was 0.5 mm a -1 (Hasholt et al, 2018).…”

Environmental change and impacts in the Kangerlussuaq area, West Greenland

“…The nearby presence of the GrIS has a dominant influence as a source for sediment and nutrients to foreland and fjord systems, and both field observations and modeling of the GrIS are important to elucidate the magnitude and change of these fluxes. Based on runoff monitoring and sample collection at the outlet of Watson River,Hasholt et al (2018) quantified the export of sediment and solutes into the fjord. Van As et al (2018) used air temperature data from Kangerlussuaq and runoff data from lake Tasersiaq, located south of the Kangerlussuaq area, to extrapolate the Watson River runoff time series back to 1949.…”