Revisiting Halosteric and Thermosteric Sea-level Rise

A global analysis of linear trends in observed ocean profile data quantifies the halosteric and thermosteric changes in sea-level and their regional patterns. Total steric change is 35mm or 0.7 mm yr-1 (27mm, 0.55 mm yr-1) integrated to a depth of 1800m (700m). These are consistent with the current best steric estimates accounting for around half of total 20th century observed sea-level rise, with the remainder attributed to mass contributions from the cryosphere and changes to terrestrial storage. For a sense of magnitude, 6mm or 20% (3mm or 10%) is due to halosteric effects. In parts of the regional oceans, depth-integrated halosteric changes can account for around 50% of the long-term total steric signal and these are found to be the leading steric change term for 34% of the global ocean. Observed regional patterns are compared to the patterns provided by the ensemble mean from the CMIP3 and available CMIP5 20th century simulations. There is a remarkable correspondence between spatial change patterns in the observations and these ensemble mean estimates, with clear, broad-scale pattern matches for the North Atlantic and Pacific Basins in long-term trends. This correspondence suggests that CMIP models are capturing the broad-scale processes which have driven changes throughout the observed record. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 IM release number is: LLNL-ABS-570169