During glacial periods, the sea level falls, because large quantities of water are stored in the massive inland glaciers. Until now, however, computer models have been unable to reconcile sea-level height with the thickness of the glaciers. Using new calculations, a team of climate researchers led by the Alfred Wegener Institute has now managed to explain this difference.
The estimated depth of the oceans and the amount of ice stored in glaciers has been based on an analysis of sediments from core samples collected from the seafloor in the tropics. These contain traces of corals that can tell us to what extent the sea level rose or fell over the millenia. This is because corals only live in well lit waters near the ocean’s surface. The sediment cores indicate that sea level was roughly 130 meters lower than it is today. However, previous models suggest that the glacial masses weren’t large enough 20,000 years ago to explain such a low sea level. For the sea level to be that low, on a global scale an additional volume of water with twice the mass of the Greenland Ice sheet would have to have been frozen.
With his new method, climate expert Evan Gowan has now reconciled sea level and glacier math. According to his calculations, the sea level at the time was estimated to be 116 meters lower than it is today. Based on his approach, there is no discrepancy of glacier mass. In his model, Gowan closely examined the geological conditions in the glaciated regions: how steep was the ice surface, where did glaciers flow and how much did the rocks and sediment at the base of the ice resist ice flow.
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research. (2021, February 23). ‘Missing ice problem’ finally solved. ScienceDaily. https://www.sciencedaily.com/releases/2021/02/210223110705.htm