Arctic Field Projects



Project Title: Inland Migration of Crevasses on the Greenland Ice Sheet (Award# 1339465)

PI: Hamilton, Gordon S (gordon.hamilton@maine.edu)
Phone: (207) 581.3446 
Institute/Department: U of Maine, Sawyer Environmental Research Laboratory 
IPY Project?
Funding Agency: US\Federal\NSF\GEO\OPP\ARC\RSL
Program Manager: Ms. Renee Crain (rcrain@nsf.gov)
Discipline(s): | Cryosphere |

Project Web Site(s):
Data: http://nsidc.org/
NSF_Award_Info: http://www.nsf.gov/awardsearch/showAward.do?AwardN...
Data: http://www.unavco.org
Data: https://arcticdata.io/

Science Summary:
The surface of the Greenland Ice Sheet experienced unprecedented melting during the 2012 summer, capping a decade of summers with above average melt extent and duration. Melting covered ~97% of the ice sheet during its 2012 peak and lasted almost two months longer than the 1979-2011 average. This sustained intensified melt has led to down-wasting of the surface, and has also played a role in accelerated ice flow by supplying runoff to enhance subglacial sliding. Altogether, melting has accounted for about half of the ice sheet's increased contribution to sea level rise in the last decade. Reports of surface cracks appearing at hitherto crevasse-free locations on the ice sheet have coincided with the intensified melt. These cracks can act as nascent pathways for the delivery of surface meltwater to the ice sheet bed, which might promote the inland propagation of accelerated ice flow and may lead to additional surface cracking. Their occurrence also constitutes a potential hazard to safe logistic operations (aircraft landing, surface traversing). Improved predictions of the ice sheet's response to future climate forcings as well as the ability to make informed long-term planning decisions about logistic activities in Greenland require an understanding of the processes responsible for the appearance of new surface cracks and an assessment of the likelihood that their distribution will increase with time. Intellectual Merit: The results of this project will yield new insights on seasonal patterns in flow speed along a transect extending from the ice sheet margin, where melting is extensive, to close to the summit divide, where melting occurs only occasionally. It will allow us to understand the relative effects of meltwater-induced acceleration and longitudinal flow coupling on the overall behavior of the ice sheet. The work will also advance knowledge of the processes generating surface fractures and crevasses on glaciers and ice sheets. Broader Impacts: Project findings will contribute to understanding the Greenland Ice Sheet's response to extreme climate forcing. This is a matter of global societal concern because changes in ice sheet mass balance play a major role in modulating sea level. Results of this work will also impact planning for future logistic activities in support of scientific research in Greenland and Antarctica. Raven is the primary skiway training facility for aircrews tasked with providing support in both polar regions; if training activities are curtailed in Greenland, a lack of properly certified aircrews will have a significant negative impact on the US Antarctic Program. This project will help assess the ongoing viability of the Raven training site and contribute to the search for potential new Greenland training sites

Logistics Summary:
The PI leads an investigation of surface cracks that appeared suddenly in 2012 near Raven Camp, the main training site for crews flying U.S. Air National Guard (ANG) ski-equipped aircraft (LC-130s) in Greenland. The cracks appeared during the peak melt event in 2012 and led to a temporary halt in L-130 training activities. New cracks also appeared on the route used by the Greenland Inland Traverse (GrIT) in northwest Greenland and may severely impact future traversing activities. Two hypotheses have been proposed to explain the occurrence of the cracks: one invokes the sudden drainage of a firn aquifer beneath Raven and the resulting subsidence of the overlying firn to form the cracks; the other hypothesis involves the downstream acceleration of ice flow leading to an increase in strain rates and the formation of true crevasses. If the second hypothesis is correct, crack sizes and their frequency of occurrence are likely to increase in the future. In 2013 a field team of 2 will travel to Kangerlussuaq in early May, late May, and again in late July to test those hypotheses by carrying out GPS surveys of ice motion and strain rate. After arriving via the ANG logistics chain in early May, they will base from Kangerlussuaq and use chartered fixed-wing support to make several aerial surveys of the region. During the early May and late July trips, the researchers will also travel via LC-130 to Raven Camp and resurvey a strain grid established there the year before. Also in late July, the PI will fly via the AMC to Thule Air Base to study, via aerial surveys aboard a helicopter chartered by CPS in support of the GrIT project, the crevassed region of the GrIT route, with particular interest paid to a recently identified crevasse. In addition to the field work, this project’s researchers also will make a detailed assessment of crevasse distributions through time using very high-resolution satellite imagery. In 2014, two people will visit Greenland in late July. Work to be carried out focuses on recovering instruments deployed in summer 2013, and resurveying the margin strain grid and Raven strain grid. The group will also collect shallow ice samples (~upper 50 cm) to conduct microstructural analyses to understand the role of crystal fabric in crevasse formation. They will base from Kangerlussuaq and use chartered helicopter support. In late August, team members will fly via the AMC to Thule Air Base to study, via aerial surveys aboard a helicopter chartered by CPS in support of the GrIT project, the crevassed region of the GrIT route, with particular interest paid to a recently identified crevasse. In addition to the field work, this project’s researchers also will make a detailed assessment of crevasse distributions through time using very high-resolution satellite imagery.

CPS will provide Air National Guard (ANG) coordination for cargo between NY/Kanger/Raven, including retrograde samples transported via cold deck; reimbursement for commercial travel between Maine and Kangerlussuaq (2014 only); KISS user days; rental truck in Kangerlussuaq; helicopter charters; snowmachines, fuel, and camp/safety equipment; lab spaces; travel tickets and clearances to/from Thule; and lodging while on Thule Base. All other arrangements will be made and paid for by the grant.
SeasonField SiteDate InDate Out#People
2013Greenland - Kangerlussuaq05 / 04 / 2013 08 / 21 / 20134
2013Greenland - Raven05 / 07 / 2013 08 / 17 / 20133
2013Greenland - Thule07 / 25 / 2013 08 / 02 / 20131
2014Greenland - Kangerlussuaq07 / 30 / 2014 08 / 09 / 20142
2014Greenland - Raven08 / 07 / 2014 08 / 07 / 20142
2014Greenland - Thule09 / 11 / 2014 09 / 19 / 20141
 


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