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This week from AGU: Rainfall and landslide risk, lava lake, winds hasten glacial melting

American Geophysical Union

From AGU's blogs: How rain falls - not just how much - may alter landslide risk

New research finds that it's not just the amount of rain that falls on a hillside, but the pattern of rainfall that matters when trying to determine how likely a slope is to give way. This new information could improve forecasts of landslides, which are typically hard to predict, said the scientists conducting the research.

Different rainfall patterns--a short, heavy deluge, a light, steady downpour, or sporadic showers--will trigger different numbers of landslides with varying amounts of debris, according to the new study published online in Water Resources Research, a journal of the American Geophysical Union.

The study's authors used this information about rainfall variability to develop a new model that factors in how different regions of a hillside redistribute the weight of the water depending on the amount, length and location of the rainfall.

From this week's Eos: Toward Another Lava Lake in the Virunga Volcanic Field?

Earlier this year, a red glow became visible atop Nyamulagira, a volcano in the East African Rift. Helicopter flights soon confirmed lava fountains inside a pit crater on the volcano's central caldera.

From AGU's journals: Changing winds cause melting of coastal Antarctic glaciers

Anthropogenically induced changes in winds in the Southern Hemisphere are playing a key role in recent warming of subsurface waters around Antarctica, according to a new study by Spence et al. The warming water increases melting of coastal glaciers and thus could affect sea levels in the future.

Since the 1950s, westerly winds in the Southern Hemisphere have been picking up and shifting poleward, due to anthropogenic global climate warming. The authors combined half a century of atmospheric data with a model of the coastal currents that shuttle water around Antarctic glaciers. Easterly winds create surface currents that pump cool fresh water downward, the authors demonstrated, keeping the temperatures at the bases of glaciers cool and pushing warm water away. But the westerly winds reduce these currents, and as a result, warm water creeps inward and upward toward the shore, where it heats up glaciers. Warm temperatures along grounding lines--where the glacier meets the ocean floor--especially increase melting.

The authors find that the changing westerly winds are responsible for an increase in water temperature of 2.5 °C (36.5 °F) on the western side of the Antarctic Peninsula, at critical depths of 200-700 meters (656-2297 feet). They calculate that the total heat increase in that region was enough to cause a sea level rise of 5.5 millimeters (0.22 inches) over the past 50 years (assuming that the grounded ice remains stationary). Based on the strong relationship between temperature increases and these winds, the authors think that current projections for sea level rise may be significantly underestimated.


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