Sea level rise – bonus impacts

One of the extra impacts from sea level rise is that the spin of the Earth will slow down. The melting of polar ice sheets is already moving weight from the poles into the oceans, which generally are not at the poles.

We’re losing about a gigatonne of ice per day, roughly a cubic kilometre (give or take quite a bit). This is a reasonable chunk of ice now melted and heading towards the equator. Still, the Earth weighs about five million billion gigatonnes.

The overall effect depends upon what ice melts, and where the water ends up in the oceans, coz the oceans are not that flat, overall. So the numbers are pretty vague right now. A metre of sea level rise might lengthen each day by maybe 0.01 seconds. For comparison, the eearthquake that caused the Asian tsunami to lengthen by maybe 0.000002 seconds. So 0.01 seconds is huge, as these things go.

(Also, 1 metre sea level rise means approximately 100 million people homeless, give or take err… quite a lot.)

7 thoughts on “Sea level rise – bonus impacts”

  1. Units

    Still, the Earth weighs about five million billion gigatonnes.

    So that’s 5 * 10^6 * 10^9 * 10^9 * 10^3 kg = 5 * 10^27 kg? (Assuming the USA billion rather than the UK billion.) If Wikipedia is to be believed, that’s off by about 10^3; Wikipedia claims approx Earth’s mass is 6 * 10^24.

    Still 1 * 10^9 in 6 * 10^24 is 1 in 6 * 10^15, which is a pretty small fraction. Even if a gigatonne of ice melting per day does seem to be rather a lot.


    1. Re: Units

      Ah, you spotted my completely deliberate and not accidental at all, honest guv, mistake of mixing gigatonnes and gigakilogrammes.


      1. Re: Units

        And looking now, I see I did the same thing in my second statement. It should be:

        1 * 10^9 (giga) * 10^3 (tonne) = 1 * 10^12 (kg) in 6 * 10^24 (kg) = 1 in 6 * 10^12. Which is a somewhat larger fraction.

        Gigatonnes seems the wrong unit; it all seems to be the fault of choosing “kilogram” as the SI unit with its pre-built-in scale factor and consequent difficulty in pronouncing things (terakilograms anyone?). (Perhaps that should be petagrams, which unfortunately is sufficiently unused for most people to have no idea of its scale.)


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