This week from AGU: Sea-level spikes, volcanic risk, volcanos cause drought

(Press-News.org) From AGU's blogs: Sea-level spikes can harm beaches worse than hurricane

Unforeseen, short-term increases in sea level caused by strong winds, pressure changes and fluctuating ocean currents can cause more damage to beaches on the East Coast over the course of a year than a powerful hurricane making landfall, according to a new study. The new research suggests that these sea-level anomalies could be more of a threat to coastal homes and businesses than previously thought, and could become higher and more frequent as a result of climate change, according to a new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

From this week's Eos: Assessing Volcanic Risk in Saudi Arabia: An Integrated Approach

The Kingdom of Saudi Arabia has numerous large volcanic fields, known locally as "harrats." The largest of these, Harrat Rahat, produced a basaltic fissure eruption in 1256 A.D. with lava flows traveling within 20 kilometers of the city Al-Madinah, which has a current population of 1.5 million plus an additional 3 million pilgrims annually. With more than 950 visible vents and periodic seismic swarms, an understanding of the risk of future eruptions in this volcanic field is vital. The Volcanic Risk in Saudi Arabia (VORISA) project was developed as a multidisciplinary international research collaboration that integrates geological, geophysical, hazard, and risk studies in this important area.

From AGU's journals: Large volcanic eruptions cause drought in eastern China

In most cases, the annual East Asian Monsoon brings heavy rains and widespread flooding to southeast China and drought conditions to the northeast. At various points throughout history, however, large volcanic eruptions have upset the regular behavior of the monsoon.

Sulfate aerosols injected high into the atmosphere by powerful eruptions can lower the land-sea temperature contrast that powers the monsoon circulation. How this altered aerosol forcing affects precipitation is not entirely clear, however, as climate models do not always agree with observations of the nature and scale of the effect.

Using two independent records of historical volcanic activity along with two different measures of rainfall, including one 3,000-year long record derived from local flood and drought observations, Zhuo et al. analyzes how large volcanic eruptions changed the conditions on the ground for the period 1368 to 1911. Understanding the effect of sulfate aerosols on monsoon behavior is particularly important now, as researchers explore aerosol seeding as a means of climate engineering.

The authors find that large Northern Hemispheric volcanic eruptions cause strong droughts in much of eastern China. The drought begins in the north in the second or third summer following an eruption and slowly moves southward over the next 2 to 3 years. They find that the severity of the drought scales with the amount of aerosol injected into the atmosphere, and that it takes 4 to 5 years for precipitation to recover. The drying pattern agrees with observations from three large modern eruptions.

China's northeast is the country's major grain-producing region. The results suggest that any geoengineering schemes meant to mimic the effect of a large volcanic eruption could potentially trigger devastating consequences for China's food supply.

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