Planethopia

Earth has experienced more than 20 ice age cycles during the past 2 million years. The changing climates of the ice ages changed the last episode of human evolution. Always changing shorelines modified migraton routes for humans and also other species on Earth. Some of most productive soils in America, Europe and China developed on silt deposited during glacial times.

As the continental ice sheets decayed and grew level of the sea rose and dropped. The lowest sea level was about 130 meters below today level and the highest several meters above present level. We can see here that sea level is good but not too good measure of the waxing and wanning of ice sheets. It is important to be very accurate in those measurements, for instance 6m error is equivalent to the presence or absence of all the ice that is currently on Greenland.

Some works on sea-level history found a connection between sea level and the intensity on Northern hemispfere summer sunlight called insolation. Sunlight variations have periods of ~23 000, ~41 000 and ~100 000 years and the ice ages have the same periodicities, but for last several cycles dominant period is ~100 000 years. Interesting, isn’t?

Some scientists have questions relating to the flow and bend of the solid Earth, such that sea level is not only dependent on ice volume. Earth’s mass distribution and shape are one of the factors maybe. Gravitional field changes continually as the water redistributes between ice sheets and oceans during ice age cycles but those changes on Earth are very slow because of the high viscosity of Earth’s mantle.