Sea Level Rebound After Cooling?

So sea levels can fall due to cooling... How can sea level come back up after runaway cooling?

In order to understand how sea level can rebound (rise) after sea level fall, and in particular to understand the repetitive oscillations or cycles observed in the former section, it is important to consider changes in ice volume (growth vs. melting). It is easy to see how more and more ice could lead to more and more cooling (and lower and lower sea levels as ice builds up on land) as light energy from the sun is reflected back into space with no chance of being absorbed by earth and turned into thermal energy that would contribute to melting.

In order to warm earth and melt ice so it can return to the ocean and elevate sea levels, in a repetitive - metronome-like process, a mechanism to counteract cooling is needed. It is hard to conceptualize of a plate tectonic (intrinsic) mechanism, like formation of the Panamanian Isthmus, that would produce the metronome-like set of repetitive cycles as observed in the Hansen curve (see Figure 4.24). As such, the Earth needs to either receive more light energy that is converted to heat energy, or more of the light energy that is received needs to be converted to heat and be retained so that it melts more ice each year than accumulates, resulting in a net reduction of glacial ice.

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Figure 4.26: View of the north pole of Earth near the end of the Pleistocene Epoch versus today. Large continental glaciers covered much of northern North America (nearly all of Canada and portions of the United States) as well as much of northern Europe. In addition to continental glaciers, the extent of sea ice was much larger in the Pleistocene. This combination resulted in extensive albedo and helped promote more cooling.
<div class="credit">Credit: NOAA Paleoclimatology Program