Velocity response of Petermann Glacier, northwest Greenland to past and future calving events

Emily A. Hill, G. Hilmar Gudmundsson, J. Rachel Carr, Chris R. Stokes
2018 The Cryosphere Discussions  
<p><strong>Abstract.</strong> Dynamic ice discharge from outlet glaciers across the Greenland ice sheet has increased since the beginning of the 21st century. Calving from floating ice tongues that buttress these outlets can accelerate ice flow and discharge of grounded ice. However, little is known about the dynamic impact of ice tongue loss in Greenland compared to ice shelf collapse in Antarctica. The rapidly flowing (∼<span class="thinspace"></span>1000<span class="thinspace"></span>m<span
more » ... ace"></span>m<span class="thinspace"></span>a<sup>&amp;minus;1</sup>) Petermann Glacier in north-west Greenland has one of the ice sheet's last remaining ice tongues, but it lost ∼<span class="thinspace"></span>50&amp;ndash;60<span class="thinspace"></span>% (∼<span class="thinspace"></span>40<span class="thinspace"></span>km in length) of this tongue via two large calving events in 2010 and 2012. The glacier showed a limited velocity response to these calving events, but it is unclear how sensitive it is to future ice tongue loss. Here, we use an ice flow model (Úa) to assess the instantaneous velocity response of Petermann Glacier to past and future calving events. Our results confirm that the glacier was dynamically insensitive to large calving events in 2010 and 2012 (<<span class="thinspace"></span>10<span class="thinspace"></span>% annual acceleration). We then simulate the future loss of similar sized sections to the 2012 calving event (∼<span class="thinspace"></span>8<span class="thinspace"></span>km long) of the ice tongue back to the grounding line. We conclude that thin, soft sections of the ice tongue ><span class="thinspace"></span>12<span class="thinspace"></span>km away from the grounding line, provide little frontal buttressing, and removing them is unlikely to significantly increase ice velocity or discharge. However, once calving removes ice within 12<span class="thinspace"></span>km of the grounding line, loss of these thicker and stiffer sections of ice tongue could perturb stresses at the grounding line enough to substantially increase inland flow speeds (∼<span class="thinspace"></span>900<span class="thinspace"></span>m<span class="thinspace"></span>a<sup>&amp;minus;1</sup>), grounded ice discharge, and Petermann Glacier's contribution to global sea level rise.</p>
doi:10.5194/tc-2018-162 fatcat:cekcejl52bhvnopgjlvvmldyhu