Past, Present, and Future Pacific Sea-Level Change

Satellite altimeters have provided near-global coverage of the ocean with a continuous record now approaching 3 decades. These observations have led to definitive evidence of an increase in global mean sea-level, while offering a depiction of the spatial variability in sea-level change. As a result of the increasing length of the altimeter record, studies have sought to understand and detect the emergence of a forced or anthropogenic response in sea-level. The central idea behind these studies is that the altimeter record is now long enough that the influence of interannual to decadal variability is reduced and does not obscure underlying regional trends in the way that it did for the early part of the altimeter record. Two locations-the western tropical Pacific and the northeastern Pacific off the west coast of the United States-are noteworthy for their sea-level variations during the altimeter era, exhibiting large departures from the global average albeit in opposite directions. In this study, we examine satellite altimeter-measured sea-level in these two regions. The goals are to understand the evolution of the sea-level trend, and determine what can be inferred about future sea-level change from the satellite altimeter record. We find that in the two locations considered here the altimetry record is still too short to rule out natural variability contributions to the trend on the order of 1 mm/yr. Using longer records from tide-gauge observations and models, an assessment of the potential future changes in both regions is made for both regions.

Automated summary

Satellite altimeters have provided global coverage of ocean observations for nearly three decades, showing evidence of global mean sea-level rise and spatial variability. However, the influence of natural variability on sea-level trends still cannot be ruled out due to the short length of the record.