CoAuthors

Benjamin Hamlington (NASA Jet Propulsion Laboratory, California Institute of Technology, United States); Brett Buzzanga (NASA Jet Propulsion Laboratory, California Institute of Technology, United States); Christopher Piecuch (Woods Hole Oceanographic Institution, US); Philip Thompson (University of Hawai`i at Manoa, US)

Across the globe, coastal communities are responding to current sea level rise and planning for the future. The rate of regional sea level rise is not spatially uniform and deviates from the global average due to both forced and natural variability. In order to provide coastal practitioners with the best regionally-relevant sea level information, we must determine the sources of variability in the current sea level record, with an eye toward how this will change in the future. The impact of natural variability on regional SLR is challenging to separate and quantify in the still relatively short satellite record, and will change as the satellite altimeter record lengthens. Here we analyze the full 30-year record of satellite altimetry sea level data to assess the relationship between regional SLR and the natural climate variability.

Regional differences in sea level trends are impacted by various modes of climate variability and respond to differences in the dominant regional forcing. We present analysis of the spatial variability in sea level trends across the globe, as well as the influence of record length on the interpretation of these patterns. Time series of high and low regional sea level, delineated relative to the global 30-year sea level trend, reveal inversely oscillating regions of high and low trends and relatively small regions that closely track the globally-averaged sea level signal. Similar time series based instead on regional averages delineated by the spatial structure of the first mode empirical orthogonal function loading vector also show oscillatory fluctuations. Globally, regions of low mean sea level oscillate in phase with the Interdecadal Pacific Oscillation, indicating a strong influence of the Pacific Ocean in the regional averages. Spatial patterns of the first mode loading vector and sea level trends show similar structure throughout the Pacific, but differ over the Indian and Atlantic Oceans. While the 30-year trend in the Indian Ocean is positive everywhere, the first mode loading vector is indicative of the Indian Ocean Dipole. Contrastingly, sea level trends are negligible throughout most of the Atlantic with the exception of positive trends along the Central and North American east coasts and negative trends in the North Atlantic. This structure is of opposite sign in the first mode loading vector. The global distribution of the trend evolution reveals the critical influence of natural interannual and decadal variability on the rates of acceleration – or how much and how quickly the trends change over a given time period. Consideration of the processes that drive these periods of high and low rates of sea level change could be helpful in planning for future sea level rise impacts. Natural variability will continue to impact the satellite altimeter-measured SLR pattern as the record lengthens, emphasizing the critical need for continued sea level monitoring at a global scale, particularly in regions not well instrumented with tide gauges and in situ nearshore sensors.