West Antarctica ice-sheet calving due mainly to geology

Sometime between Monday 10th July and Wednesday 12th July, a 2,239 square mile section of Larsen C ice sheet finally broke away. As the media put it, that’s about the size of the State of Delaware. The Larsen C ice sheet is located in the Weddell Sea near the tip of the West Antarctica peninsula. The resulting iceberg has been designated Larson A68. Some of the media claimed this calving was due to human-induced global warming and portends a scary future. (See LA Times, New York Times , and CNN stories. CNN headline: “That huge iceberg should freak you out” )

The LA Times story does note that in the year 2000, a 4,200 square mile chuck of ice calved from the Ross Sea ice shelf.

A scientist from Project MIDAS, a UK-based Antarctic research project investigating the effects of a warming climate on the Larsen C ice shelf in West Antarctica, said that they were “not aware of any link to human-induced climate change…” (Source)

The geology of West Antarctica is discussed in a long post by geologist James Kamis (read full post).

As shown on Kamis’ figure 2 above, West Antarctica is within a major rift zone which is pulling the continent apart. There are also 61 recognized volcanos on the surface, on the sea bed, and under the ice, all of which provide heat and tectonic instability. Kamis contends that the geology is driving ice shelf calving.

Calving of giant ice bergs is not a new phenomenon. A 1956 newspaper story found by Tony Heller of RealScience.com documents two large icebergs. One, spotted by a Navy icebreaker was 208 miles long and 60 miles wide (12,480 square miles, about the size of Massachusetts and Connecticut combined). During the same year another iceberg measuring 200 miles long and 10 miles wide calved from the Ross Ice Shelf. The same story notes that the Navy Hydrographic Office reports a 100 mile by 100 mile iceberg (10,000 square miles) spotted by a whaling ship in 1927. (Source) Remember that good coverage of ice shelf calving is made possible by satellite observation which began in 1979. Before that, it was by chance observation from ships.

See also:

The “Unstoppable Collapse” of the West Antarctic ice sheet

Geology is responsible for some phenomena blamed on global warming

A Simple Question for Climate Alarmists

Greenland ice melt due to geothermal heat flux

The Greenland ice sheet loses about 227 gigatonnes of ice per year and contributes about 0.7 millimeters to the currently observed mean sea level change of about 3 mm per year.  New research from the Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, claims that “The Greenland ice sheet is melting from below, caused by a high heat flow from the mantle into the lithosphere.”  See press release here, and an enlargement of the graphic here.

The melting is quite variable spatially and reflects the relatively thin crust under Greenland. “The Greenland lithosphere is 2.8 to 1.7 billion years old and is only about 70 to 80 kilometers thick under Central Greenland.” Climate models fail to take this phenomenon into effect.

The German researchers say, “We have run the model over a simulated period of three million years, and taken into account measurements from ice cores and independent magnetic and seismic data. Our model calculations are in good agreement with the measurements. Both the thickness of the ice sheet as well as the temperature at its base are depicted very accurately.”

“The temperature at the base of the ice, and therefore the current dynamics of the Greenland ice sheet is the result of the interaction between the heat flow from the earth’s interior and the temperature changes associated with glacial cycles.”

Citation: Petrunin, A. G., Rogozhina, I., Vaughan, A. P. M., Kukkonen, I. T., Kaban, M. K., Koulakov, I. & Thomas, M., “Heat flux variations beneath central Greenland’s ice due to anomalously thin lithosphere”, Advance Online Publication, Nature Geoscience, 11. 08. 2013, http://dx.doi.org/10.1038/ngeo1898)

See also:

Greenland “melting” and media hype

The Arctic-Antarctic seesaw