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Short Summary
Main recommendation: Glaciologists should use satellite and airborne observations together with numeric models to uncover what is hidden inside the Greenland ice sheet, so that sea level rise can be better forecast and planned for. The speaker, Kristin Poinar, argues that liquid water trapped in a "glacier aquifer" may be draining through crevasses to the bedrock and ocean, potentially speeding ice loss. Narrowing projection uncertainty is presented as the field's core task.
Key Points
- Satellites and aircraft, including a radar-equipped Air Force cargo plane operated by NASA, are revolutionizing glaciology by continuously revealing new facts about ice sheets.
- Greenland has lost so much ice since 2002 that the meltwater would knee-deep flood Australia, and the loss rate would have stunned glaciologists 50 years ago.
- Radar reveals hidden bedrock and water because ice is transparent to radar, while liquid water absorbs it, as in a microwave oven.
- Summer meltwater pools into a liquid "glacier aquifer" roughly seven stories beneath the surface, insulated by snow and kept liquid year after year.
- Newly observed crevasses near the aquifer may let water fracture the ice downward to the base of the ice sheet, about 1,000 meters deep, and from there to the ocean.
- Projections for the next 80 years put sea level rise at least 20 centimeters and perhaps up to one meter, with a wide uncertainty range.
Details Worth Noting
- Concrete instructions: No step-by-step procedure for the public is given. The only actionable guidance is for scientists: use remote sensing data alongside numeric models (equations run on supercomputers) to answer whether crevasses are water-filled, how deep they go, and whether they reach the bedrock. Adapt engineering fracture equations used for aluminum, steel, and plastics to model ice cracking under water pressure, as the speaker did.
- The speaker's numeric model found that aquifer inflow can overcome refreezing in ice around -15°C (about kitchen-freezer temperature) if the flow rate is high enough, which it was at this site.
- The aquifer water contributes to the roughly 3 millimeters per year of global sea level rise, and the speaker suggests it may be "punching above its weight" by possibly accelerating ice flow to the ocean. This question was still being investigated.
- The speaker compares the crevasse-driven process to fracking, where pressurized fluids fracture rock, and notes that a single crack is enough to start the process.
- The microwave analogy: an ice cube won't melt in a microwave, but wet ice will, because water absorbs microwave energy.
- Greenland is about the size of Mexico, and its ice is roughly two miles thick at the deepest point.
Bottom Line
Liquid water hidden in Greenland's ice may be accelerating ice loss, so better models built on new satellite and radar data are needed to narrow sea level rise projections.