Detection of land ice and hydrology contributions to the total regional sea-level changes over the past 40 years using GRACE time series and other data

Contemporary regional sea level changes arise from multiple factors: land, ocean and atmospheric mass variations; ocean dynamical processes including ocean water density changes and ocean mass redistributions; Inverted Barometer (IB) effect due to atmospheric pressure changes.

Here, we are primarily concerned with the determination of the regional sea level variations from contemporary land ice mass and land hydrology variations in the past 40 years. Changes in mass load on land, over the ocean and in the atmosphere, cause the sea level fingerprint (SLF). Each source of mass changes, including ice sheets, glaciers and ice caps (GIC), land hydrology, atmosphere, and ocean, produces a unique spatial pattern, or fingerprint of relative sea levels due to self-attraction, loading effects and rotational feedbacks.

We seek to detect the contributions of land ice and hydrology on total regional sea level changes by integrating datasets that span four decades, including satellite observations, tide gauge records, surface mass balance from regional atmospheric climate models, Glacial Isostatic Adjustment corrections, and oceanic and atmospheric model outputs. On shorter time scales, sea level changes due to land ice and hydrology changes are difficult to distinguish from ocean dynamics; however, as land ice mass loss accumulates, the land ice-SLF signals will become increasingly dominant, thus detection of its contributions in the regional sea level may be possible.

We use reconstructions of the mass balance changes of the Greenland and Antarctic ice sheets using Component Approach going back to the 1970s. We generate extended GIC mass balance time series beyond the GRACE period to replace sparse, traditional assessments. We then quantify the regional and global mean contributions of ice sheets and land hydrology to sea level rise. Finally, we compare the cumulative signal from SLF with tide gauge records around the world, corrected for earth dynamics, to detect the land ice SLF in the record. This work was performed at UC Irvine and at Caltech's Jet Propulsion Laboratory under a contract with NASA's Sea Level Science Program.