Photo Friday: The Drygalski Ice Tongue

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.

Drygalski Ice Tongue, Scott Coast, McMurdo Sound, Antarctica – February 6th, 2020 image is about 181 kilometers wide (Image: Pierre Markuse)

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.

The iceberg C-16 collides with Drygalski ice tongue on 30 March 2006 (Source: NASA/WikiCommons).

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.”

Looking right down the Drygalski Ice Tongue from the air (Image: Santiago de la Peña)

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.

Read More on GlacierHub:

Thwaites Glacier in Antarctica is Now Causing Earthquakes

Photo Friday: “Antarctica” – An Exhibit Showcasing Lamont Scientists’ Photos from the Field

Video of the Week: “Return to Natural––Documenting the Tasman Glacier”

Roundup: Rock Glaciers, Ice Tongues and Flood Warnings

Roundup: Rock Glaciers, Floating Glaciers, and Flood Warnings

Ecology of Active Rock Glaciers

From Boreas: “Active rock glaciers are periglacial landforms (areas that lie adjacent to a glacier or ice sheet that freeze and thaw) consisting of coarse debris with interstitial ice (ice formed in the narrow space between rocks and sediment) or ice-core. Recent studies showed that such landforms are able to support plant and arthropod life and could act as warm-stage refugia for cold-adapted species due to their microclimate features and thermal inertia. However, integrated research comparing active rock glaciers with surrounding landforms to outline their ecological peculiarities is still scarce… Our data show remarkable differences between stable slopes and unstable landforms as a whole, while few differences occur between active scree slopes and active rock glaciers: such landforms show similar soil features but different ground surface temperatures (lower on active rock glaciers) and different occurrence of cold-adapted species (more frequent/abundant on active rock glaciers)… The role of active rock glaciers as potential warm-stage refugia for cold-adapted species is supported by our data; however, at least in the European Alps, their role in this may be less important than that of debris-covered glaciers, which are able to host cold-adapted species even below the climatic tree line.”

Read more about the role of active rock glaciers as potential warm-stage refugia here:

Rock glaciers in the European Alps (source: M Barton / Flickr).
Rock glaciers in the European Alps (source: M Barton/Flickr).

 

Fluid-Ice Structure Interaction of the Drygalski Ice Tongue

From UTAS: “The Drygalski Ice Tongue (DIT) is the largest floating glacier in Antarctica, extending approximately 120km into McMurdo Sound, and exhibits a significant influence upon the prevailing northward current, as the ice draft (measurement of ice thickness below the waterline) of the majority of the DIT is greater than the depth of the observed well-mixed surface layer. This influence is difficult to characterize using conventional methods such as in-situ LADCP (Lowered Acoustic Doppler Current Profiler) measurements, vertically collected profiles or long-term moorings as these are generally relatively spatially sparse datasets. In order to better relate measurements across the entire region of influence of the DIT region, a set of Computational Fluid Dynamics simulations (uses numerical analysis to analyze fluid flows) were conducted using a generalized topography of a mid-span transect of the DIT… Numerical modeling of environmental flows around ice structures advances the knowledge of the fluid dynamics of the system in not only the region surrounding the DIT but also provides a clearer insight into fluid-ice structure interactions and heat flux in the system. This may lead to a better understanding of the long-term fate of floating glaciers.”

Learn more about fluid-ice structure interactions here:

Drygalski ice tonguet (source: cohnveno / Flickr).
Drygalski ice tonguet (source: cohnveno/Flickr).

 

Flood Early Warning Systems (EWSs) in Bhutan

From ICIMOD: “Bhutan experiences frequent hydrometeorological disasters. In terms of relative exposure to flood risk as a percentage of population, Bhutan ranks fourth highest in the Asia-Pacific region, with 1.7% of its total population exposed to flood risk. It is likely that climate change will increase the frequency and severity of flood disasters in Bhutan. Inequalities in society are often amplified at the times of disaster and people living in poverty, especially women, the elderly, and children, are particularly vulnerable to flood hazards. Timely and reliable flood forecasting and early warnings that consider the needs of both women and men can contribute to saving lives and property. Early warning systems (EWSs) that are people-centered, accurate, timely, and understandable to communities at risk and that recommend the appropriate action to be taken by vulnerable communities can save people more effectively. To improve the understanding of existing early warning systems (EWSs) in the region and their effectiveness, ICIMOD has conducted an assessment of flood EWS in four countries (Bangladesh, Bhutan, Nepal, and Pakistan) from a gendered perspective. The objective is to support the development of timely, reliable, and effective systems that can save lives and livelihoods.”

Read more about flood early warning systems in Bhutan here:

UNDP Bhutan GOLF Thorthormi lake workers (source: UNDP / Flickr).
UNDP Bhutan GOLF Thorthormi lake workers (source: UNDP/Flickr).