The Thwaites Glacier, often called the “Doomsday Glacier,” sits in a vulnerable position in West Antarctica, draining ice from a large section of the West Antarctic Ice Sheet (WAIS) into the Amundsen Sea. This glacier is a global focal point for climate change due to the immense threat it poses to worldwide sea levels. Its ominous nickname reflects scientific concern that its unstable nature could accelerate ice loss across the entire region. Monitoring Thwaites is a high-priority task for researchers predicting the future rate of global sea level rise.
The Thwaites Glacier Context
The Thwaites Glacier is one of the largest and most rapidly changing glaciers on Earth, covering approximately 192,000 square kilometers—roughly the size of Florida or Great Britain. It is the widest glacier in the world, with an ocean-facing front extending about 120 kilometers. Its flow rate has nearly doubled over the last three decades.
The glacier’s vulnerability is primarily due to the geological structure beneath it, particularly at its grounding line. This is the point where the ice transitions from resting on the bedrock to floating on the ocean as an ice shelf. The grounding line is retreating because it rests on a retrograde slope—a seabed that slopes downward inland. As warm ocean water gains access to this deeper cavity, it causes melting from below, which lifts the ice off the bedrock and accelerates the retreat.
The thinning of the floating ice shelf, which acts as a restraint, allows the grounded ice behind it to move more quickly toward the sea. Scientists are closely watching this fracturing ice shelf, as its collapse would remove a significant barrier to the glacier’s flow. The ongoing International Thwaites Glacier Collaboration (ITGC) involves over 100 scientists focused on understanding these dynamics to better forecast the glacier’s retreat.
Direct Contribution to Sea Level Rise
The direct contribution to global ocean volume is the most certain consequence of the Thwaites Glacier’s complete melt. If the glacier were to fully collapse, the volume of ice it contains would be sufficient to raise global sea levels by approximately 65 centimeters, or about 25 inches.
This amount of sea level rise would have immediate, tangible effects on densely populated coastal regions and low-lying island nations. A rise of 25 inches would dramatically increase the frequency and severity of coastal flooding, transforming routine high tides into damaging events. Infrastructure in major coastal cities, including ports, wastewater treatment plants, and transportation systems, would be permanently compromised or require costly relocation and fortification.
For small island developing states and nations with extensive delta regions, a rise of this magnitude represents an existential threat. Coastal erosion would accelerate, and saltwater intrusion would contaminate freshwater aquifers and agricultural lands, rendering large areas uninhabitable. The displacement of millions of people worldwide would become a likely consequence as coastlines are permanently reshaped by the rising water.
The West Antarctic Instability Trigger
The true danger of the Thwaites Glacier is its role as a stabilizing force for the much larger West Antarctic Ice Sheet (WAIS). Thwaites currently functions as a natural buttress, slowing the flow of ice from the interior of the ice sheet toward the ocean. The collapse of Thwaites would essentially remove the cork from the bottle, initiating the Marine Ice Sheet Instability (MISI).
The MISI mechanism is a runaway process driven by the retrograde slope beneath the ice sheet. As the grounding line retreats into deeper water, the exposed ice front becomes thicker and more unstable, which increases the ice flow rate. This accelerated flow causes the grounding line to retreat further and faster, creating a self-perpetuating cycle of collapse.
Once the Thwaites buttress is gone, the surrounding glaciers, including the Pine Island Glacier, would be exposed to the destabilizing forces of the ocean, leading to an irreversible chain reaction across the WAIS. The meltwater from Thwaites alone is not the “doomsday” scenario, but rather the subsequent destabilization of the entire ice sheet it holds back. If the whole WAIS were to collapse, it would release enough ice to cause an additional global sea level rise of about 3.3 meters, or over 10 feet, potentially occurring over several centuries.
Impacts on Global Ocean Systems
Beyond the change in sea level, the influx of cold, fresh water from the melting Thwaites Glacier would significantly alter the global ocean system. The Southern Ocean, which encircles Antarctica, is the site of deep-water formation that drives global ocean circulation. This circulation, often called the thermohaline circulation, acts like a planetary conveyor belt, distributing heat, salt, and nutrients around the globe.
The meltwater, being less dense than the surrounding saltwater, would form a buoyant layer on the ocean surface. This layer could inhibit the sinking of cold, dense water that forms the Antarctic Bottom Water (AABW). A reduction in AABW formation could weaken the entire global ocean current system, affecting climate patterns worldwide. Changes in this deep-water formation would also affect the Antarctic Circumpolar Current (ACC), the world’s largest ocean current, which regulates global climate.
The localized marine ecosystems in the Amundsen Sea would experience immediate biological impacts from changes in salinity and temperature. The alteration of the water column structure could disrupt the distribution and lifecycle of foundational species like krill, a primary food source for whales, seals, and penguins. This shift in the environment would cascade through the entire Antarctic food web.