Mass balance of Greenland and the Canadian Ice Caps from combined altimetry and GRACE inversion

• Main Authors: Forsberg, René, Simonsen, Sebastian Bjerregaard, Sørensen, Louise Sandberg, Nilsson, Johan
• Format: Conference Object
• Language: English
• Published: 2016
• Subjects: Arctic; Greenland; Baffin; Ice cap; Ice Sheet
• Online Access: https://orbit.dtu.dk/en/publications/7614530d-9068-445f-b723-44826a9f24f9; http://lps16.esa.int/page_session132.php#1741p

The combination of GRACE and altimetry data may yield a high resolution mass balance time series of the Greenlandice sheet, highlighting the varying individual mass loss behaviour of major glaciers. By including the Canadian arctic ice caps in the estimation, a more reliable estimate of the mass loss of both Greenlandand the Canadian ice caps may be obtained, minimizing the leakage errors otherwise unavoidable by GRACE. Actually, the absolute value of the Greenlandice sheet mass loss is highly dependent on methods and how the effects of Arctic Canadian ice caps are separated in the GRACE signal; here altimetry data and firn models may provide important constraints.In the presentation we outline the basis of the joint estimation method, including corrections for firn density and compaction, and use CryoSat and EnviSat data together with GRACE data to provide composite time series of mass loss of the ice caps and ice sheet basins for the period 2003-15. This period shows a marked increase of ice sheet melt, especially in NW and NE Greenland, but also show large variability, with the melt anomaly year of 2012 showing a record mass loss, followed by 2013 with essentially no Greenland mass loss at all, and lately return to the “normal” mass loss rate. While GRACE sees these later year anomalies quite clearly, the CryoSat data are affected strongly by the icesheet-wide 2012 melt event, where change in CryoSat radar penetration in the firn results in an erroneous mass gain estimate over central parts of theGreenlandice sheet. The overall estimate of mass loss trend forGreenlandduring the CryoSat period yields values around -280 GT/yr, with the Canadian ice cap mass loss estimated at around -40 GT/yr and -25 GT/yr for the Baffin and Ellesmere regions, respectively. The used estimation methods can readily be extended to other altimetry mission data, such as Sentinel-3 and AltiKa, and could also potentially be used to further integrate other EO parameters such as ice velocity changes of the major outlet glaciers, as ...