At the risk of oversimplifying, the
effects of groundwater storage can be differentiated between
shallow -
aquifer effects that modulate global sea level on year to year and decade to decade timeframes, versus deep
aquifer effects that modulate sea level trends over centuries and millennia.
In contrast to La Nina induced
shallow -
aquifer effects, deep
aquifers have been filled with meltwater from the last Ice Age, and that water is slowly and steadily seeping back into the oceans today.