Hi Richard, Most predictions of sea level rise assume that the ocean has a fixed size and that more water from melting glaciers and icecaps translates to higher sea level. This is not strictly true. Indeed, measured sea level rise has always been a fraction of what scientists predicted. The reason is that the ocean does NOT have a fixed size. The thin crust of the earth at the bottom of the oceans floats on molten magma. As melting ice from any warming land mass adds to the volume of water in the sea, hydrostatic pressure increases and pushes the ocean floor down deeper into the magma. Simultaneously, the weight and pressure of ice on mountaintops decreases and allows magma to push upwards to make space for the magma which is displaced from the bottom of the oceans, creating a circle of mass movement and a tendency towards equilibrium. Furthermore, the thin crust of the earth is not static. It floats on molten magma and when solar and lunar gravity effects combine in different vectors and changes with solar apogee and perigee, oceans change slightly in depth and pressure, sometimes causing islands to rise very slowly and then fall slowly. Add to that higher than normal wind speeds and equinox king tides and we see more island lakes being swamped. The slight actual mean global rise in sea level through more water coming from warming continents is slight and only a minor contribution.
Thanks Mike. Very interesting. And glacial rebound is also hugely important. We know the presence or absence of glacial ice is very important because sea levels have increased by about 130 metres since the 'depths' of the most recent glacial maximum 20,000 years ago. See https://en.wikipedia.org/wiki/Past_sea_level
Yes Richard, Geological evidence along sea shores show that sea levels have been much higher and lower thousands of years ago but unfortunately we can only guess at the causes. Devastating strikes by massive meteors are plausible explanations and scientists should look for correlations in historical time for the previous five mass extinction events versus drastic sea level changes.
Hi Richard, Most predictions of sea level rise assume that the ocean has a fixed size and that more water from melting glaciers and icecaps translates to higher sea level. This is not strictly true. Indeed, measured sea level rise has always been a fraction of what scientists predicted. The reason is that the ocean does NOT have a fixed size. The thin crust of the earth at the bottom of the oceans floats on molten magma. As melting ice from any warming land mass adds to the volume of water in the sea, hydrostatic pressure increases and pushes the ocean floor down deeper into the magma. Simultaneously, the weight and pressure of ice on mountaintops decreases and allows magma to push upwards to make space for the magma which is displaced from the bottom of the oceans, creating a circle of mass movement and a tendency towards equilibrium. Furthermore, the thin crust of the earth is not static. It floats on molten magma and when solar and lunar gravity effects combine in different vectors and changes with solar apogee and perigee, oceans change slightly in depth and pressure, sometimes causing islands to rise very slowly and then fall slowly. Add to that higher than normal wind speeds and equinox king tides and we see more island lakes being swamped. The slight actual mean global rise in sea level through more water coming from warming continents is slight and only a minor contribution.
Thanks Mike. Very interesting. And glacial rebound is also hugely important. We know the presence or absence of glacial ice is very important because sea levels have increased by about 130 metres since the 'depths' of the most recent glacial maximum 20,000 years ago. See https://en.wikipedia.org/wiki/Past_sea_level
Yes Richard, Geological evidence along sea shores show that sea levels have been much higher and lower thousands of years ago but unfortunately we can only guess at the causes. Devastating strikes by massive meteors are plausible explanations and scientists should look for correlations in historical time for the previous five mass extinction events versus drastic sea level changes.