Basal melting and Eemian ice along the main ice ridge in Northern Greenland – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2009 > Basal melting and Eemi...

Basal melting and Eemian ice along the main ice ridge in Northern Greenland

PhD defence by Susanne Lilja Buchardt

Abstract:
The variation of the basal melt rate and the location of the Eemian layer in the ice column are investigated along the ice divide between the NorthGRIP and NEEM ice core drill sites in northern Greenland. At NorthGRIP an ice core was drilled in the period 1996-2004, and the stable isotope record (δ18O) from this core is used to infer past accumulation rates at the site. Under the assumption that the present accumulation rate pattern in the area has remained unchanged during the past glacial cycle, this accumulation history is used to calculate the accumulation rates at other sites along the line. A Dansgaard-Johnsen model is then used to simulate the ice flow along the flow line from NorthGRIP to NEEM. One- as well as two-dimensional approaches are taken. The basal melt rates and other unknown flow parameters are determined using a Monte Carlo method. The Monte Carlo solution is constrained by isochrones revealed in radio-echo sounding images of the ice. The obtained results indicate a high spatial variability in the basal melt rate in the area, and values between zero and 25 mm/yr are found. The results indicate that there is little or no basal melting at NEEM. The location of the Eemian layer is determined using the Monte Carlo determined flow parameters. The obtained results agree with observations at NorthGRIP and predict a full Eemian record to be found at NEEM. The layer is estimated to be 70 m thick and located in the depth range 2230-2300 m, which is 200 m above bedrock.

Assessment committee:
Christine Schøtt Hvidberg, NBI (Chair)
Edwin D. Waddington, University of Washington
David G. Vaughan, British Antarctic Survey

Advisor :
Dorthe Dahl-Jensen