Concerning Evidence for Fingerprints of Glacial Melting

Abstract

Recent investigations of tide gauge and hydrographic data point to the conclusion that twentieth-century global sealevel rise was about 1.8 mm/y, with significant decadal and longer variability. Ocean thermal expansion can account for about 0.5 mm/y of the trend, leaving an additional ∼1.3 mm/y water equivalent that must have come from other sources. Greenland, Antarctica, and small glaciers are obvious candidates, and “fingerprints” of their contributions must occur because additions of glacial ice or meltwater to the oceans will not cause a globally uniform rate of sealevel rise. As ice melts or is discharged, Earth will respond elastically, and the geoid will also adjust. The result is that large changes in relative sea level will occur near the area of melting or discharge, and significant (∼20%) deviations from a uniform global rise will occur antipodal to the source. Thus, several authors have used trends of relative sea-level rise obtained from tide gauge data to investigate possible contributions from Greenland, Antarctica, and other sources of global sea-level rise. In this paper, we consider the fingerprint question morphologically by examining the regional variations of relative sea-level change for evidence of these fingerprints. Unambiguous evidence for fingerprints of glacial melting was not found, most likely due to the presence of other signals present in sea-level records that cannot easily be distinguished.