Using satellite records and global climate models, scientists have shown that sea level rise is accelerating. Although sea level data from the past 23 years diverged from this long term trend, researchers demonstrate that the abnormal cooling caused by the 1991 eruption of Mt. Pinatubo concealed the long-term trend.
A high-resolution record of global sea level has been available since the 1992 launch of the TOPEX/Poseidon satellite altimeter. The satellite uses radar to measure the distance between it and the earth, to take a global measurement of sea level. The somewhat constant increase in sea level over the past two decades has puzzled scientists because it is not in agreement with sea level predictions based on accelerations in rising global temperatures and ice loss. That is until a recent study in Scientific Reports found that sea level increase is accelerating at the moment, even though the acceleration is not immediately apparent from the record. The eruption of Mt. Pinatubo caused a global cooling event and therefore a drop in sea level (because cooler waters take up less volume). After the cooling event ended, the oceans rapidly regained their heat and sea level rose sharply (because warmer waters expand in volume). The rate of sea level change, when averaged over the decades, does not seem to be accelerating because of these rapid changes. However, when the effects of the volcanic event are included in the prediction, the background rate of sea level change is faster today than in the past.
The research team estimates that sea level rise is accelerating at a rate of 0.12mm per year every year. For this acceleration, the rate of sea level rise will increase from an average 2.7mm per year in the decade from 2003-2012 to an average 3.9mm per year from 2013-2022. The Pinatubo anomaly makes clear that this value can be affected by other events, such as rates of ice loss and potentially volcanic eruptions. While 0.12mm/yr2 may seem like a small number, it could have a major effect on sea levels in the coming decades. If sea level rise continued to accelerate at this rate, we would expect an additional 0.5ft in the next 50 years, and 2ft in the next century on top of the current rate of increase.
Is the detection of accelerated sea level rise imminent? Scientific Reports
Seas aren’t just rising, scientists say – it’s worse than that. They’re speeding up. The Washington Post