Articles | Volume 9, issue 5
Research article
04 Sep 2015
Research article |  | 04 Sep 2015

Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial mass balance from surface mass balance

J. A. Bonin and D. P. Chambers

Abstract. Mass change over Greenland can be caused by either changes in the glacial dynamic mass balance (DMB) or the surface mass balance (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire mass column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate cumulative SMB from DMB with GRACE, using a least squares inversion technique with knowledge of the location of the glaciers. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from DMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 10 at a resolution of 90 × 90 would provide the accuracy needed for the interannual cumulative SMB and DMB to be accurately separated.

Short summary
Separating surface mass balance from glacial mass balance over Greenland would provide important climatological information and constraints for models, but due to poor spatial resolution, the GRACE gravity satellites cannot ordinarily accomplish this. We demonstrate a least-squares technique which allows us to do so, in theory. However we also find that the GRACE errors are too large to make it practical for real-world use at this time. About a 9-fold reduction in noise would be needed.