The Thwaites Glacier, Rising Sea Levels, and the Future of Coastal Cities

March 19, 2019 by Sylvie Yudin

The Thwaites Glacier comprises one third of the mass that has been lost from the Amundsen Sea Embayment.

Scientists have recently discovered that the Thwaites Glacier, a key component of the West Antarctic glacial system, is melting faster than expected. Since many of the world’s population and financial centers are located along coastlines, the situation unfolding at the Thwaites Glacier is particularly alarming. How drastically are melting glaciers impacting sea levels, and how will governments respond to these shifts?

Temperatures on Earth have been rising, and these warmer temperatures present massive implications for our global system.[1] An especially troubling aspect of rising temperatures is the melting of glaciers, which causes sea levels to rise. To be sure, throughout Earth’s 4.6 billion-year existence, sea levels have experienced substantial periods of both rising and falling, but what makes the current sea level rise notable is the increased speed at which it is occurring.[2] Melting ice sheets cause sea levels to rise, which will have especially harmful impacts on coastal regions. Over six hundred million people reside on coastal areas located less than ten meters above the sea level and over one hundred million people live within just three feet of average sea level.[3] Many of the world’s major cities and commercial centers, such as Shanghai, New York, Tokyo, and Bangkok, are located near coastal plains or river deltas, placing them at risk for harms associated with rising sea levels.[4] Because the majority of the world’s population lives along the coast and cities along the cost would be threatened by rising sea levels, it is important for scientists to observe melting ice sheets and identify which glaciers, if they were to melt, would pose the greatest risk to civilization.[5] These studies will help to inform strategies on how to mitigate or adapt to the anticipated rise.

Ice sheets are masses of glacial land that extend for over twenty thousand square miles.[6] Earth has two ice sheets: the Antarctic ice sheet, which is 5.4 million square miles large, and the Greenland ice sheet, which is 7.2 million square miles large.[7] These ice sheets hold over ninety-nine percent of Earth’s freshwater.[8] Glaciers are ice masses that are composed of fallen snow that has compressed over time.[9] Glaciers represent nearly ten percent of Earth’s total land area, with the majority of glaciers located in polar regions such as Antarctica, Greenland and the Canadian Arctic.[10] Glaciers are very sensitive to changes in climate, and since the beginning of the twentieth century, the vast majority of glaciers have been retreating at higher rates than ever seen before.[11]

Melting glaciers are a major source of sea level rise. Most of the glacial retreat that has occurred in the past fifty years is due to greenhouse gases, which absorb heat and increase atmospheric temperatures.[12] The burning of fossil fuels, deforestation, and farming have increased the presence of dust and soot in the atmosphere, which also contributes to glacial retreat.[13] Increased temperatures melt the surface of glaciers, creating ponds of meltwater that then fracture the ice shelf as they drain through cracks in the ice. This is called hydrofracturing, and this process can happen quickly, over the span of months.[14]

The West Antarctic ice sheet is viewed as the most vulnerable part of Earth’s major ice sheets.[15] The Amundsen Sea Embayment is a part of West Antarctica and is a leading contributor to rising sea levels.[16] The Thwaites Glacier comprises one third of the mass that has been lost from the Amundsen Sea Embayment.[17] NASA’s Operation IceBridge is an airborne mission that began in 2010. It is the world’s largest airborne study of polar ice.[18] Operation IceBridge examines the relationship between the polar regions and global climate. It was Operation IceBridge that found Thwaites’ cavity via radar. Scientists now realize how rapidly the ice at Thwaites was melting.[19]

The recently discovered rapid melting of the Thwaites Glacier has alarmed scientists and presents dire implications for coastal cities. The Thwaites Glacier – Amundsen Sea system comprises intricate interactions between the ice, ocean, and atmosphere.[20] The newly learnt cavity underlying the Thwaites Glacier is approximately six miles long, one thousand feet deep, and encompasses fourteen billion tons of ice.[21] Meltwater from the Thwaites Glacier makes up about four percent of the rise in global sea level.[22] If the glacier were to collapse due to its newly discovered rapid loss of ice, a disaster scientists believe may happen within the next fifty to one hundred years, sea levels would rise two feet.[23] In addition to being important due its large mass, the Thwaites Glacier acts as a sort of backstop for nearby glaciers, and if it were to melt neighboring glaciers would likely melt as well, causing another eight feet of additional sea level rise.[24] Thwaites has been referred to as the “wild card glacier” and a “lynchpin” because it is both a key part of West Antarctica and represents scientists first opportunity to gain a comprehensive understanding of glacial melting.[25]

Measuring glaciers is difficult work because there is no viable way to measure Antarctic glaciers from the ground level over a long period of time.[26] As a result, scientists utilize satellites and other airborne methods to detect a glacier’s surface height and flow speed.[27] Scientists also look to changes in the glacier’s grounding line – the point where glaciers begin to float on top of seawater- to determine retreat.[28] Many Antarctic glaciers outspread for miles past their grounding lines. This poses a risk to sea levels; as glaciers melt they begin to float over land, causing the grounding line to retreat and increasing exposure of the underside of the glacier to sea water.[29] This then causes the rate at which the glacier will melt to increase.[30] At the Thwaites grounding line, warm water that has been pushed up from the open ocean causes the ice to melt at a rate of tens of feet a year.[31] Melting is compounded by the meeting of cold air and freezing ocean water which creates salty water. The salty water then mixes with the deeper water and the meltwater.[32] Further, the Amundsen Sea Low wind system brings warm wet air from north of the ice sheet.[33] Indeed, due to a combination of all these factors throughout the past forty years, glaciers in the Amundsen Sea Sector have thinned at a quickening, unstable, and likely irreversible rate.[34] Scientists have found that Thwaites is becoming unstuck from a bedrock ridge at a rate at about .4 to .5 miles per year since 1992. Even though this rate of grounding line retreat is steady, the rate of melting is incredibly high.[35]

On January 29, 2019, as part of the International Thwaites Glacier Collaboration, over twenty scientists from the United Kingdom, United States, and Sweden embarked on the first ship-based research voyage to the Thwaites Glacier.[36] This twenty five million dollar project funded by the U.S. National Science Foundation and the United Kingdom Natural Environment Research Council will last five years. The team of scientists will spend fifty days on the Nathaniel B. Palmer, a U.S. icebreaker ship, collecting data. Data will be gathered through the use of autonomous vehicles, ocean gliders, and tagged elephant and Weddell seals.[37] The seals are key to the research, as they move freely in places that scientists find hard to reach, such as near the ice front and under the sea ice.[38]

Scientists will also study the seafloor using swath bathymetry to determine how the landscape under the glacier has historically impacted the glacier.[39] Bathymetric data is the measurement of the depth of a body of water. This data can be expressed in the form of a map depicting the shapes and elevation of land beneath the water.[40] The Bathymetry data that has already been collected of the Thwaites Glacier shows the presence of deep channels in the seabed in the region. When probed, these channels have indicated water with temperatures above freezing.[41] The scientists will also collect data by drilling though ice to reach the underlying bedrock. Researchers will collect samples of the rock cores to gain geological evidence of the retreat of the ice sheet over time.[42] Sea level changes in the area over the past ten thousand years will be reconstructed. This will be key in determining whether there is a chance that the current retreat of Thwaites is reversible.[43] Sediments collected will show how the ice has changed over time via its interactions with the ocean and in what ways the environment is changing.[44] Samples of rocks, penguin bones, and shells from islands close by will be carbon dated to shed light on how sea level has changed over the past five thousand years.[45]

Thwaites is not the only glacier in West Antarctica causing worry among scientists. The Pine Island Glacier is one of the most active parts of the Antarctic ice sheet, draining a major share of the West Antarctic ice sheet into an Amundsen Sea embayment.[46] NASA scientists, in 2011, discovered an enormous crack running across the Pine Island Glacier.[47] By examining sediment cored from below the Pine Island Glacier ice shelf, scientists discovered that in 1945 the glacier’s grounding line withdrew from the sea floor ridge and that by 1970, the ice shelf had ungrounded.[48] Pine Island Glacier has historically released icebergs into the Amundsen Sea approximately every six years.[49] However, since 2013, the rate of iceberg releases has increased to an almost annual occurrence: Pine Island Glacier has released icebergs in 2013, 2015, 2017, and 2018.[50] In 2018, NASA satellite Sentinel-1observed the Pine Island Glacier releasing nearly three hundred square kilometers of ice.[51] NASA believes that this increased frequency is due to ice shelf thinning.[52]

Scientists are alarmed because sea level rise will have many drastic effects. There will be higher levels of flooding in coastal lands and saltwater will enter the surface waters in these areas.[53] Saltwater invasion into groundwater poses an obvious threat to drinking water, irrigation, and farming. Scientists have already begun planning for a course of action to help civilization deal with the threat of rising sea levels. The two strategies are broadly defined as mitigation and adaption.[54] Mitigation aims to steady levels of greenhouse gases.[55] Mitigation would require efforts on a global scale and would be helpful in stabilizing the rate of sea level rise and decreases the impacts of a rising sea level. Adaption includes efforts made by local or national governments and would lead to humans altering their actions in response to actual or expected climate changes.[56] A measure of adaption would be humans moving away from the coast. Governments would need to take proactive steps and engage in landuse planning and development. Coastal areas, as they are at extreme risk, would ideally engage in both mitigation and adaptive practices.[57] Robert J. Nicholls, in Planning for the Impacts of Sea Level Rise, details four main aspects of adaption that should be taken into account. He describes adaption as a “multistage process” that would include: (1) increasing awareness and information, (2) planning and designing, (3) evaluating, and (4) monitoring and evaluating.[58]

There are many cities and countries that have already begun to make plans in anticipation of rising sea levels. Much of the Netherlands is located below sea level. This has led the Netherlands to make comprehensive efforts to both mitigate and adapt to the problems posed by rising sea levels. In 2007, the Dutch government created a Delta Committee to develop strategies to ensure the viability of the country’s coastal regions. The Committee plans to nourish beaches and restore natural estuary and tidal systems.[59] The Delta Program is estimated to cost the Netherlands 1.6 billion euros a year until 2050 and nine hundred euros for every year after.[60] Unfortunately, not all countries are wealthy enough to undertake such projects. For instance, the Marshall Islands are home to seventy-five thousand people and are located less than seven feet above sea level.[61] The president of the Marshall Islands, Hilda Heine, has stated that plans need to be made to physically raise the lands on which the Marshall Islands are located.[62] Because this project would cost more than the country can afford, President Heine is calling to gain funds via donations and partnerships.[63] While rising sea levels will impact coastal cities, a nation’s wealth plays an important role in determining the success of its mitigation and adoption strategies.

As science continues to progress and we gain more precise predictions on future rises in sea level, governments will no doubt be better able to make plans for mitigation and adaption. Of course, while some governments are more proactive than others, accurate and detailed scientific data will hopefully convince the governments in coastal regions that have yet to seriously consider the dangers of sea level rise to examine the issue more closely and take further steps to plan accordingly. Over the next five years, data collected via the International Thwaites Glacier Collaboration will surely play a key role in helping scientists form a more complete picture of the amount sea levels could rise within the next generation.

[1] Daniel Glick, The Big Thaw, National Geographic (Feb. 19, 2019)

[2] Id.

[3] Id.

[4] Id.

[5] Seals to Act as Sentinels of Remote Antarctic Glacier, International Thwaites Glacier Collaboration (Jan. 29, 2019)

[6] Quick Facts on Ice Sheets, National Snow & Ice Data Center, (last visited March 2, 2019).

[7] Id.

[8] Id.

[9] What is a Glacier?, National Snow & Ice Data Center, (last visited March 2, 2019).

[10] Id.

[11] Glaciers and Climate Change?, National Snow & Ice Data Center, (last visited March 2, 2019).

[12] Id.

[13] Id.

[14] Laura Naranjo & Agnieszka Gautier, The International Thwaites Glacier Collaboration, National Snow & Ice Data Center (Jan. 28, 2019)

[15] Douglas Fox, The West Antarctic Ice Sheet Seems to be Good at Collapsing, National Geographic, (June 13. 2018)

[16] P. Milillo et al, Heterogeneous Retreat and Ice Melt of Thwaites Glacier, West Antarctica, 5.1 Science Advances: Geology 1, 1 (Jan. 30, 2019).

[17] P. Milillo et al, supra note 16, at 1.

[18] IceBridge Mission Overview, NASA (last visited March 2, 2019).

[19] NASA/Jet Propulsion Laboratory & Carol Rasmussen, Huge Cavity in Antarctic Glacier Signals Raid Decay, Science Daily, (Feb. 1, 2019)

[20] About the Science, International Thwaites Glacier Collaboration, (last visited March 2, 2019).

[21] Denise Chow, A Hole Opens Up Under Antarctic Glacier- Big Enough to Fit Two-thirds of Manhattan, NBC (Feb. 4, 2019)

[22] Carolyn Beeler, Just How Unstable is the Massive Thwaites Glacier? Scientists are About to Find Out, PRI (May 1, 2018)

[23] Denise Chow, supra note 21.

[24] NASA/Jet Propulsion Laboratory & Carol Rasmussen, supra note 19.

[25] Seals to Act as Sentinels of Remote Antarctic Glacier, supra note 5.

[26] NASA/Jet Propulsion Laboratory & Carol Rasmussen, supra note 19.

[27] Id.

[28] Bethan Davies, Grounding Lines, Antarctic Glaciers, (Sept. 15, 2014)

[29] NASA/Jet Propulsion Laboratory & Carol Rasmussen, supra note 19.

[30] Id.

[31] About the Science, supra note 20.

[32] Id.

[33] Id.

[34] Lawrence Livermore National Laboratory, Thinning, Retreat of West Antarctic Glacier Began in 1940s, Science Daily, (Nov. 23, 2016)

[35] NASA/Jet Propulsion Laboratory & Carol Rasmussen, supra note 19.

[36] Seals to Act as Sentinels of Remote Antarctic Glacier, supra note 5.

[37] Id.

[38] Id.

[39] Id.

[40] Bathymetry, National Geographic, (last visited March 2, 2019).

[41] About the Science, supra note 20.

[42] Geological History Constraints on the Magnitude of Grounding-Line Retreat in the Thwaites Glacier System, International Thwaites Glacier Collaboration, (last visited March 2, 2019).

[43] Id.

[44] Seals to Act as Sentinels of Remote Antarctic Glacier, supra note 5.

[45] Id.

[46] Robert A. Bindschadler, History of Lower Pine Island Glacier, West Antarctica, from Landsat Imagery, 48.163 Journal of Glaciology 536, 536 (2002).

[47] Lawrence Livermore National Laboratory, supra note 34.

[48] Id.

[49] Pine Island Glacier Quickly Drops Another Iceberg, NASA, (Nov. 7, 2018)

[50] Id.

[51] Id.

[52] Id.

[53] Robert J. Nicholls, Planning for the Impacts of Sea Level Rise, 24.2 Oceanogrpahy 144, 147 (2011).

[54] Id. at 151.

[55] Responding to Climate Change, NASA, (last visited March 2, 2019).

[56] Id.

[57] Robert J. Nicholls, supra note 53, at 151.

[58] Id. at 153.

[59] Pavel Kabat, Louise Fresco et al, Dutch Coasts in Transition, 2 Nature Geoscience, 450, 451 (2009).

[60] Id.

[61] Lauren Tousignant, Marshall Islands Plans to Raise its Land to Survive Rising Sea Levels, NY Post (Feb. 26, 2019)

[62] Id.

[63] Id.