Videobreak: Rob Dunbar – The threat of ocean acidification

Posted on September 13, 2010 | 5 Comments
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5 Responses to Videobreak: Rob Dunbar – The threat of ocean acidification

  1. Joachim | September 16, 2010 at 4:54 am | Reply

    He claims that if the Ross ice shelf, a floating body of ice, melts, the oceans will rise. From Archimedes we know that as long as the ice floats it displaces the same amount of water in the ocean as its mass, and so when it melts it could not possibly cause any rise in ocean levels.

  2. caerbannog | September 16, 2010 at 11:03 am | Reply

    The Ross Ice Shelf holds back the West Antarctic Ice Sheet (WAIS). If the Ross Ice Shelf goes, glaciers draining the WAIS will discharge ice into the water to replace it — so if the Ross Ice Shelf goes, sea-levels *will*rise.

    • Joachim | September 16, 2010 at 5:26 pm | Reply

      You make it sound like the WAIS is not grounded. The Ross Ice Shelf would not be enough to stop WAIS if the condions were right for it to move into the ocean. Also, Dunbar was NOT talking about WAIS, but the Ross Ice shelf.

  3. caerbannog | September 17, 2010 at 9:29 pm | Reply

    The Ross Ice Shelf owes its existence to the WAIS. It is clear and obvious from the physical evidence in the sediment cores that the ice that forms the Ross Ice Shelf originated on the WAIS. From the transcript of the talk:

    You know, we saw this in the core samples as they came up. We saw these alternations between sediments that look like this — there’s gravel and cobbles in there and a bunch of sand. That’s the kind of material in the deep sea. It can only get there if it’s carried out by ice. So we know there’s an ice shelf overhead.

    The bottom line is, if the Ross Ice Shelf disappears, then that means that the WAIS that feeds it has also disappeared (or has been greatly reduced in size). Archimedes’ law is irrelevant here.

    If you respond to this, please do some homework and learn a little Earth science first — Rush Limbaugh talking-points do not impress me.

  4. luminous beauty | September 20, 2010 at 1:40 pm | Reply

    Joachim,

    You are over-simplifying the dynamics of ice shelves. They are only partially supported by bouyancy. They are also supported by cantilever forces from behind the grounding line. These forces are, in general, equalized at the calving face. As an ice sheet disintegrates, the increase in dynamic ice flow from above the grounding line and greater calving is additive to the ocean mass, effectively increasing sea level.

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