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This week from AGU: Gulf of Mexico erosion, Grand Canyon sandbars, rainfall fluctuations

American Geophysical Union

  • From AGU's blogs: Flooding, erosion risks rise as Gulf of Mexico waves loom larger

Waves in the northern Gulf of Mexico are higher than they were 30 years ago, contributing to a greater risk of coastal erosion and flooding in Florida, Alabama, Mississippi and Louisiana, according to a new study in Geophysical Research Letters.

  • From Eos.org: Building Sandbars in the Grand Canyon

Annual controlled floods from one of America's largest dams are rebuilding the sandbars of the iconic Colorado River, according to a new article by U.S. Geological Survey scientists in Eos. These simulated floods redistribute sand and mud, which helps develop this critical feature, they write in an accompanying blog post.

  • From AGU's journals: Rainfall Fluctuations Hinder Projections of Future Extremes

Scientists highly value multicentury records of weather because they can provide valuable insights into climatic changes and extremes. One station in Padua, Italy, has conducted daily observations of rainfall since 1725. Detailed data sets going back this far provide scientists a unique opportunity to better understand how climate fluctuates over time and how atmospheric and climatic cycles affect an area's weather patterns.

However, no one had ever analyzed the Padua data set at the daily level. Marani and Zanetti performed the first analysis of this station's data down to the individual day; despite some gaps in the record, the authors were able to study 268 full years of measurements.

Specifically, the authors document extremes in rainfall and assess how these extremes changed over time in response to atmospheric circulation patterns and climate change The team finds that annual rainfall slightly decreased over the period of study, and the number of rainy days, although fluctuating, showed no major trend. However, rainfall extremes seem to follow a very different behavior. Extremes slightly intensified and exhibited wide oscillations, partly in sync with a dominant climatic pattern known as the North Atlantic Oscillation (NAO).

The authors observe at least five distinct cyclical oscillations in the rainfall data, with cycle durations ranging from roughly 17-21 years to 145-172 years. These long-term oscillations and weather patterns are likely to have affected precipitation in other regions as well. As a result, the authors conclude, past observations, especially from records lasting a century or less, cannot necessarily shed light on future climate extremes.

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