Abstract
Abstract. Rising sea levels and increased surface melting of the Greenland ice sheet have heightened the need for direct observations of meltwater release from the ice edge to ocean. Buoyant sediment plumes that develop in fjords downstream of outlet glaciers are controlled by numerous factors, including meltwater runoff. Here, Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery is used to average surface suspended sediment concentration (SSC) in fjords around ∼80% of Greenland from 2000–2009. Spatial and temporal patterns in SSC are compared with positive-degree-days (PDD), a proxy for surface melting, from the Polar MM5 regional climate model. Over this decade significant geographic covariance occurred between ice sheet PDD and fjord SSC, with outlet type (land- vs. marine-terminating glaciers) also important. In general, high SSC is associated with high PDD and/or a high proportion of land-terminating glaciers. Unlike previous site-specific studies of the Watson River plume at Kangerlussuaq, temporal covariance is low, suggesting that plume dimensions best capture interannual runoff dynamics whereas SSC allows assessment of meltwater signals across much broader fjord environments around the ice sheet. Remote sensing of both plume characteristics thus offers a viable approach for observing spatial and temporal patterns of meltwater release from the Greenland ice sheet to the global ocean.
Highlights
The Greenland ice sheet is undergoing increasing melt intensity and extent (Mote, 2007; Bhattacharya et al, 2009); in response to warming air temperatures (Hanna et al, 2008; Tedesco et al, 2008; Box et al, 2009)
While ice discharge is the primary form of mass loss for most marine-terminating outlet glaciers (Mernild et al, 2010), meltwater runoff possibly contributes more than half the total mass loss for the ice sheet as a whole
Moderate Resolution Imaging Spectroradiometer (MODIS)-derived estimates of coastal fjord suspended sediment concentration (SSC) ranging from ∼0.7 to 1925 mg l−1 were retrieved all around the ice sheet except in northern Greenland where persistent sea ice precludes detection of open water (Fig. 5, Table 1)
Summary
The Greenland ice sheet is undergoing increasing melt intensity and extent (Mote, 2007; Bhattacharya et al, 2009); in response to warming air temperatures (Hanna et al, 2008; Tedesco et al, 2008; Box et al, 2009). Ice mass loss has accelerated in the last decade (Chen et al, 2006; Rignot et al, 2008), with increasing accumulation in the ice sheet interior (Box et al, 2006; Burgess et al, 2010) exceeded by losses in the marginal ablation zone (Luthcke et al, 2006; Ettema et al, 2009). Marine-terminating outlet glaciers have shown increases in total ice discharge (Rignot et al, 2004; Howat et al, 2007) and velocity (Rignot and Kanagaratnam, 2006; Joughin et al, 2010), with accelerated ice loss recently extending to the northwest (Khan et al, 2010). While ice discharge is the primary form of mass loss for most marine-terminating outlet glaciers (Mernild et al, 2010), meltwater runoff possibly contributes more than half the total mass loss for the ice sheet as a whole (van den Broeke et al, 2009).
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