Investigation of Recent Interannual Variations in the Geopotential

Recent solutions for the decadal rates in the low-degree zonal terms of the geopotential, and time series of estimated gravity fields show significant inter-annual variations in the geopotential, that cannot be attributed to the atmosphere alone. These variations make it difficult to assess the results of the long-term zonal rates, and the implications for their use as constraints on aggregate mass transport within the Earth's systems. In order to make use of the observed rates in the geopotential as a geophysical constraint it is necessary to examine many possible sources for the interannual variations, and to account for these in such analyses. Results showing the inter-annual variation in the geopotential will be given, along with comparisons with other geophysical time series, including radar derived estimates of the ice heights. At present, it does not appear that ice mass changes in Greenland or West Antarctica can account for the recent variations in the geopotential. The long-term mass balance implications will also be discussed