New England under water

From the ESRI Map Book Online volume 25: What if all the polar ice melted?

Credit: Paul Jordan, University of Rhode Island

The description from the ESRI Map Book:

This map is a depiction of Rhode Island and southeastern Massachusetts/Cape Cod inundated by a 67-meter (73-yard) sea level rise resulting from a total melting of the polar ice caps. Although an unlikely scenario, the map was created as an attention grabber for display at the University of Rhode Island 2008 Honors Colloquium Lecture Series on Global Warming.

A good map can be artistic as well as informative; in fact the two often go together. The annual ESRI map books are available online or in book form (I am happy to own a couple editions).

Grace and Peace

7 thoughts on “New England under water

  1. WebMonk

    I worked with ESRI’s software for years and collected quite a few of their map books – absolutely beautiful, even when they were mapping city utilities.

    I wouldn’t worry about all the ice from the poles melting. The global temperatures would need to rise at least 30 degrees F for that to happen. (in the main plateau of Antarctica, it only gets up to 6F at the warmest for a couple days during its “summer”)

    And for the last several decades, the Antarctic ice has been well above average and doesn’t show any signs of shrinking.


  2. geochristian


    The Map Book does call this an “unlikely scenario.” It made for an interesting poster at a climate conference.

    I agree: no scientist I know of is suggesting that global warming will lead to a complete melting of the Antarctic ice cap. The West Antarctic Ice Sheet (about 10% of the overall Antarctic ice cap) could be susceptible to melting, but the main ice cap has existed to one degree or another since the Eocene or Oligocene, and has survived (though in a shrunken state) long periods when global temperatures were 2-3 C warmer than now.

    It wouldn’t take 30 F (about 17 C) of overall global temperature increase to completely melt the Antarctic ice cap. The warmest time in the Cenozoic (the past 65 million years) was the Eocene Optimum about 50 m.y. ago, with global temperatures about 6 C warmer than at present. Antarctica was ice-free in the Eocene (an additional complicating factor is that before Antarctica separated from South America at the beginning of the Miocene (~23 m.y. ago) the Antarctic Circumpolar Current didn’t exist).

    One additional note on the map: it appears to be based on a simple “fill up the ocean basin until it hits the 67-meter contour” model, which I am sure the map creator knows is an oversimplification. Many other factors would have to be considered, such as isostasy (the weight of the water would affect the gravitational equilibrium of the continental shelves as well as that of the sea floor) and thermal expansion of the ocean as it warms.


  3. WebMonk

    Yes, I realize that after a half dozen degrees of warmth increase, there would be more changes than we can realistically model, and some of the effects could be warmer temperatures moving into the Antarctic area.

    But! It sounds so much cooler to say that it would need to rise 17C in order to just begin melting the main ice cap! :-D

    Actually, just going off the top of my head, I suspect that a dramatically warmer airmass over central Antarctica would probably start dropping off more snow, offsetting any melting, at least for a while.

    I’ve got exactly zero support for that speculation, though.


  4. geochristian

    I think WebMonk is correct: Increased temperatures would lead to more snowfall over much of Antarctica; perhaps significantly greater snowfall.

    But more snowfall does not necessarily lead to growth of glaciers. Here is some further speculation:

    1. Greater ice thickness would lead to greater flow rates, hastening the movement toward the warmer seas, and hence increasing rates of ice melting.

    2. Greater ice thickness would also lead to warmer temperatures at the base of the ice, which would lead to greater flow rates, which again leads to greater melting. Even with the frigid surface temperatures of Antarctica, the West Antarctic Ice Sheet is at freezing point at its base, due to heat escaping from the Earth’s interior (a glacier at the melting point—technically its pressure melting point—at its base is called warm-based). Parts of the main Antarctic ice sheet are also warm-based (I am not sure about the percentage). The mean annual temperature in the Antarctic interior is now −57°C (−70°F). If it were to warm by just a few degrees, there would still be no melting at the surface, but the proportion of the ice cap that is warm-based (at 0°C) would increase, leading to more rapid ice movement and basal melting.

    Glaciers are incredibly complex systems, just like global climate. In general, warmer temperatures will lead to greater melting, and cooler temperatures will lead to greater accumulation. For large ice sheets such as in Greenland and Antarctica, the response of the ice to fluctuations in climate are likely to be spread out over long periods of time.


  5. WebMonk

    “For large ice sheets such as in Greenland and Antarctica, the response of the ice to fluctuations in climate are likely to be spread out over long periods of time.”

    Not according to the IPCC. They’re crystal clear that we’ve already had really dramatic glacier shrinkage in Greenland anyway, caused by global warming of less than 1C in the last 30 years. Though, you may be right, since that part of the IPCC has had several very critical papers directed its way.

    Antarctic ice has grown pretty solidly and the temperatures there for the last decade or two are definitely on the cool side of their average temperature for the last century. I haven’t run across any good studies on Antarctic ice melting from higher temperatures. Because we haven’t (yet?) seen any temperature rises around Antarctica, there hasn’t been much impetus for such a study.


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