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Allegheny Cemetery 1-13-22-40

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Totten Glacier – East Antarctica’s Achilles Heel

The East Antarctic Ice Sheet (EAIS) has generally been considered very stable, with little concern for its disintegration compared to the West Antarctic Ice Sheet (WAIS). This is because the vast majority of the bedrock underneath the WAIS is well below sea level which is not a dominant feature of the EAIS. A recent study published in Nature Geoscience has removed this false sense of security in the East Antarctic Ice Sheet.

The team of scientists led by a researcher from the University of Texas, undertook multiple research flights over the Totten Glacier, the fastest thinning section of the East Antarctic Ice Sheet. Totten glacier has been one of the few East Antarctic glaciers that has been shown to be retreating rapidly, however scientists were unsure why. The study found that the retreat is due to warm water making its way underneath, just like many of the West Antarctic.

The Totten glacier is currently losing an amount of ice equivalent to 100 times the volume of Sydney Harbour every year, which is quite problematic as the Totten Glacier is holding back an immense amount of ice in the Aurora Basin that feeds it. (For more on the buttressing effect of ice shelves, see our previous post: http://on.fb.me/1GhocUq)

The scientists used three types of measurements in their flights, including gravitational measurements, radar measurements and laser altimetry. They measured the ice thickness and the pull of Earth’s gravity to determine how far below the ice the seafloor was. They discovered two troughs in the seafloor beneath the Totten Glacier's floating ice shelf which allow warmer water to flow underneath the ice. It seems counter intuitive, but in Antarctica it is common that warmer water is in fact deeper than colder water as the surfaces are covered by fresh water produced by melting ice. This fresh water, although super cooled, is less dense than the salty, warmer waters, and therefore the cold water floats on top.

The potential sea level rise associated with the melting of the Aurora Basin/Totten Glacier Catchment is approximately 3.5m. Parts of the Northen Hemisphere will feel this more, which will be explained in a future post.

-MJA

Image Credit: Calving front of ice shelf: T. van Ommen, Australian Antarctic Division Map: Jamin Greenbaum, Australian Antarctic Division

Fort Gaines, constructed in the 1850’s, was designed by Joseph G. Totten. Totten was, along with Simon Bernard, one of the original members of the board of engineers placed in charge of fortifications. Totten designed many of the later fortifications of the Third System, and was the foremost fortification engineer in the United States during this time. Fort Gaines shows a different design philosophy than many of the earlier fortifications, and is much simpler than many of the Third System forts. This is because the Fort Gaines defended a minor channel into Mobile Bay, while Fort Morgan was located very close to the main channel.

Much like Fort Morgan, Fort Gaines has two distinct eras of fortification, the original Third System fort, and later Endicott period gun batteries. These will be covered together, since the Endicott batteries are not very extensive.

Fort Gaines is an interesting example of a late Third System fortification. Although less elaborate than some of the earlier fortifications, it has many unique and interesting features. Fort Gaines is an Alabama State Park, and is located on the eastern tip of Dauphin Island, near Mobile, Alabama.

Construction of Fort Gaines Fort Gaines, constructed in the 1850's, was designed by Joseph G. Totten. Totten was, along with Simon…

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