Surface velocity of the Northeast Greenland Ice Stream (NEGIS): assessment of interior velocities derived from satellite data by GPS
<p>The Northeast Greenland Ice Stream (NEGIS) extends around 600 km upstream from the coast to its onset near the ice divide in interior Greenland. Several maps of surface velocity and topography of interior Greenland exist, but their accuracy is not well constrained by in situ obse...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-10-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/14/3487/2020/tc-14-3487-2020.pdf |
| Summary: | <p>The Northeast Greenland Ice Stream (NEGIS) extends around
600 km upstream from the coast to its onset near the ice divide in interior
Greenland. Several maps of surface velocity and topography of interior
Greenland exist, but their accuracy is not well constrained by in situ
observations. Here we present the results from a GPS mapping of surface
velocity in an area located approximately 150 km from the ice divide near
the East Greenland Ice-core Project (EastGRIP) deep-drilling site. A GPS
strain net consisting of 63 poles was established and observed over the
years 2015–2019. The strain net covers an area of 35 km by 40 km, including
both shear margins. The ice flows with a uniform surface speed of
approximately 55 m a<span class="inline-formula"><sup>−1</sup></span> within a central flow band with longitudinal and
transverse strain rates on the order of 10<span class="inline-formula"><sup>−4</sup></span> a<span class="inline-formula"><sup>−1</sup></span> and increasing by
an order of magnitude in the shear margins. We compare the GPS results to
the Arctic Digital Elevation Model and a list of satellite-derived surface
velocity products in order to evaluate these products. For each velocity
product, we determine the bias in and precision of the velocity compared to the
GPS observations, as well as the smoothing of the velocity products needed
to obtain optimal precision. The best products have a bias and a precision
of <span class="inline-formula">∼0.5</span> m a<span class="inline-formula"><sup>−1</sup></span>. We combine the GPS results with
satellite-derived products and show that organized patterns in flow and
topography emerge in NEGIS when the surface velocity exceeds
approximately 55 m a<span class="inline-formula"><sup>−1</sup></span> and are related to bedrock topography.</p> |
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| ISSN: | 1994-0416 1994-0424 |