West Antarctica is experiencing rapid changes associated with both atmospheric and oceanic warming. This atmospheric warming, along with rising ocean temperatures along the West Antarctic Peninsula, has caused the retreat of glaciers along the coast.
Caltech and JPL scientists have developed a new model that suggests the Antarctic ice shelves may be melting at an accelerated rate, which could contribute to faster sea level rise.
Their model considers an often-overlooked narrow ocean current along the Antarctic coast. It simulates how fast-flowing freshwater, melted from ice shelves, can trap dense, warm ocean water at the base of the ice, causing it to heat up and melt even more.
Andy Thompson, professor of environmental science and engineering, said: “If this mechanism we’ve been studying is active in the real world, it could mean ice shelf melt rates are 20 to 40 percent higher than the predictions of global climate models, which typically cannot simulate these strong currents near the Antarctic coast.
Scientists focused mainly on the West Antarctic Peninsula. The team has already deployed autonomous vehicles in this region, and scientists have used data from instrumented elephant seals to measure the temperature and salinity of water and ice.
The model considers the narrow Antarctic Coastal Current that runs counter-clockwise across the Antarctic continent, a current that many climate models do not include because it is so small.
Lead Research Scientist Mar Flexas said: “Large global climate models do not include this coastal current because it is so narrow – only about 20 kilometers wide, while most climate models only capture currents of 100 kilometers or more. So there is a possibility that these models may not represent future melting rates very accurately.”
The model shows how the coastal current transports fresh water from the WAP melt as it travels across the continent. The less thick freshwater travels quickly near the ocean surface and traps the relatively warm ocean seawater against the bottom of the ice shelves. After that, the ice shelves start to melt from below.
Using this method, more meltwater from the WAP can propagate global warming via the coastal current, which can accelerate melting even on West Antarctic ice shelves thousands of kilometers from the peninsula. The rapid volume loss of West Antarctic ice shelves in recent decades can be partially explained by this remote warming mechanism.
Thompson said: “There are aspects of the climate system that we are still discovering. As we have advanced in our ability to model the interactions between the ocean, ice shelves and atmosphere, we can make more accurate predictions with better constraints on uncertainty. We may need to revise some of the predictions of sea level rise in the coming decades or centuries; that’s the work we’ll be doing in the future.”
Journal reference:
- M. Mar Flexas, Andrew F. Thompson et al. Warming of the Antarctic Peninsula results in enhanced basal melting rates across West Antarctica. Advances in Science. vol 8, number 32. DOI: 10.1126/sciadv.abj9134