Knowledge of changes in ocean bottom pressure, and their relation to fluctuations in sea surface height, is important for understanding aspects of ocean circulation and climate variability; for example, facilitating estimation of ocean heat content variations and elucidating causes for regional sea level variability. However, historical measurements of bottom pressure have been extremely sparse, limiting observational understanding of the nature of ocean bottom pressure behavior on scales relevant for climate studies.
Taking advantage of nearly a decade of measurements of ocean mass variability from the Gravity Recovery and Climate Experiment (GRACE) — a collaboration between the space agencies of the United States and Germany — along with observations of sea level from satellite radar altimeter missions, AER authors Christopher Piecuch, Katherine Quinn, and Rui Ponte recently published the first observation-based investigation of the relationship between ocean bottom pressure and sea level over the global ocean on interannual time scales.
The authors found a tight relationship between sea level and bottom pressure variations over a number of oceanic regions; for example, abyssal plains in the Southern Ocean and shallow seas around the Indonesian archipelago. Their results demonstrate the high quality of mass measurements derived from GRACE, which is a “first-of-its-kind” mission, and also highlight important exceptions to the generally held paradigm that year-to-year changes in regional sea levels mostly represent redistribution of heat within the ocean.
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Shading represents standard deviations of large-scale, low-frequency ocean bottom pressure signals from the Gravity Recovery and Climate Experiment (GRACE) satellite mission in units of equivalent cm of water.