Scatter of mass changes estimates at basin scale for Greenland and Antarctica Geodynamics Department, DTU Space, Elektrovej 2800 Kgs. Lyngby, Denmark
23 Sep 2013
Received: 19 Jul 2012 – Published in The Cryosphere Discuss.: 15 Aug 2012 Abstract. During the last decade, the GRACE mission has provided valuable data for
determining the mass changes of the Greenland and Antarctic ice sheets. Yet,
discrepancies still exist in the published mass balance results, and
comprehensive analyses on the sources of errors and discrepancies are
lacking. Here, we present monthly mass changes together with trends derived
from GRACE data at basin scale for both the Greenland and Antarctic ice
sheets, and we assess the variability and errors for each of the possible
sources of discrepancies, and we do this in an unprecedented systematic way,
taking into account mass inference methods, data sets and background
models. We find a very good agreement between the monthly mass change results
derived from two independent methods, which represents a cross validation.
For the monthly solutions, we find that most of the scatter is caused by
the use of the two different data sets rather than the two different
methods applied. Besides the well-known GIA trend uncertainty, we find that
the geocenter motion and the recent de-aliasing corrections significantly
impact the trends, with contributions of +13.2 Gt yr−1 and
−20 Gt yr−1, respectively, for Antarctica, which is more affected by
these than Greenland. We show differences between the use of release RL04
and the new RL05 and confirm a lower noise content in the new release. The
overall scatter of the solutions well exceeds the uncertainties propagated
from the data errors and the leakage (as done in the past); hence we
calculate new sound total errors for the monthly solutions and the
We find that the scatter in the monthly solutions caused by applying
different estimates of geocenter motion time series (degree-1 corrections) is
significant – contributing with up to 40% of the total error.
For the whole GRACE period (2003–2011) our trend estimate for Greenland is
−234 ± 20 Gt yr−1 and −83 ± 36 Gt yr−1 for
Antarctica (−111 ± 15 Gt yr−1 in the western part). We also find a clear (with respect to our errors) increase of mass loss in the
last four years.
Revised: 15 Jun 2013 – Accepted: 15 Jul 2013 – Published: 23 Sep 2013
Citation: Barletta, V. R., Sørensen, L. S., and Forsberg, R.: Scatter of mass changes estimates at basin scale for Greenland and Antarctica, The Cryosphere, 7, 1411-1432, doi:10.5194/tc-7-1411-2013, 2013.