Ice tongues are the oddballs of the cryosphere. Extending roughly 70 kilometers (43 miles) into the sea, the Drygalski Ice Tongue, located in Antarctica’s McMurdo Sound, is the planet’s largest such feature. The National Snow and Ice Data Center define an ice tongue (sometimes called a glacial tongue) as an extension of a glacier or ice stream projecting seaward, usually afloat. Functionally, Drygalski is the floating end of the David Glacier, which reaches the sea from a valley in the Prince Albert Mountains of Victoria Land. Ranging from 14-24 kilometers (nine to 15 miles) wide, it is relatively narrow compared to its length, which distinguishes it from ice shelves and other floating ice masses.
The phallic shape sticks out like a sore thumb in a satellite image––or like a drying, cracking schmear of spackling. It is a perplexing ephemera whose very existence is under constant threat by belligerent icebergs released from the nearby Ross Ice Shelf. The massive icebergs roam the ocean freely, crashing into more fragile things, like ice tongues, and breaking them.
It’s easy to root for Drygalski’s survival, especially given the warming circumstances. Scientists estimate the ice tongue has been around for some 4,000 years, though one can imagine the number icebergs facing Drygalski with tongue-breaking potential has never been higher. In 2005 and 2006, Drygalski was struck by icebergs from the Ross Ice Shelf, which cleaved off two 27-square mile chunks in 2005 and one 39-square mile breakage in 2006.
The image (be sure to check out the high resolution image on Flickr) is a product of the Copernicus Sentinel 2 satellite, which was processed and shared by Pierre Markuse on Twitter. Markuse is based in Hamm, Germany and processes images taken from the European Space Agency’s Sentinel satellites and NASA’s Landsat orbiters. He was also responsible for the now-famous satellite image of the Camp Fire, which destroyed Paradise, California in November 2018.
Large exposed ice tongues are a uniquely Antarctic phenomenon. As GlacierHub explained in a recent post, Antarctic glaciers flow outwards horizontally, and continue on into the water as huge floating shelves that stretch miles out to sea. Greenland glaciers flow down the island’s mountainous sides and break into icebergs when they hit the water. This behavior is common where a glacier’s terminus is close to where it starts to float—also known as the grounding line.
“Basically when [Greenland glaciers] start to go afloat, they form icebergs as opposed to Antarctica, where in most places they go afloat they don’t break off instantaneously but they form these big long ice shelves—floating extensions,” glaciologist Paul Winberry told GlacierHub. “It’s completely different.”
In response to Markuse’s sharing of the Drygalski satellite image, polar researcher Santiago de la Peña, who studies ice sheet dynamics and surface mass balance in Greenland and Antarctica at the Ohio State University’s Byrd Polar and Climate Research Center, replied with the head-on image of Drygalski featured above. He added the question, “I wonder what conditions favor the formation of such a tongue here?” The head of the Earth and Mission Science Division at the European Space Agency’s (ESA) Earth Observation program, Mark Drinkwater, replied. “Cold Ross Sea shelf waters, and no warm circumpolar deep water to destabilize it,” Drinkwater said.
For more earth observations, including cryosphere images, Markuse maintains a personal blog of the images he processes. You’ll want to bookmark it.
Editor’s note: After this article was published, ESA chief Mark Drinkwater tweeted the image below: “Here’s my all-time favorite Envisat image of Drygalski ice tongue and the most spectacular Ross Sea iceberg flotilla I’ve ever reported on.” The photo features an armada of icebergs, the largest of which is the aforementioned aircraft carrier-shaped berg named B-15A, which impacted the ice tongue, shattering the tip. Iceberg B-15A measured around 295 kilometers (183 mi) long and 37 kilometers (23 mi) wide, with a surface area of 11,000 square kilometers (4,200 square miles). It holds the record for the largest iceberg in the world––bigger than the country of Jamaica––so large it even has it’s own Wikipedia page. Also wandering the Ross Sea at the time were icebergs B-15K, C-16, and B-15J.