Tuesday, April 15, 2014

New paper finds storm activity in Alaska is at relatively low levels compared to the past 9,600 years

A paper published today in Quaternary Research reconstructs storm activity in Alaska over the past 9,600 years and finds storm activity at the end of the record [2000 AD] was at relatively low levels in comparison to the rest of the Holocene [past ~10,000 years]. The authors also find storm activity was more variable from 1500 AD - 1850 AD during the Little Ice Age, which contradicts alarmist claims that warming causes increased extreme weather.  

Top graph of BSI % is a proxy for storminess, with lower levels indicating more storminess, as shown at bottom of graph. Horizontal axis is thousands of years before the present. 

The abundance of sedimentary organic material from two lakes was used to infer past Holocene storminess on Adak Island where frequent storms generate abundant rainfall and extensive cloud cover. Andrew and Heart Lakes are located 10 km apart; their contrasting physical characteristics cause the sedimentary organic matter to respond differently to storms. Their records were synchronized using correlated tephra beds. Sedimentation rates increased between 4.0 and 3.5 ka in both lakes. Over the instrumental period, Andrew Lake biogenic-silica content (BSi) is most strongly correlated with winter sunlight availability, which influences photosynthetic production, and river input, which influences the dilution of BSi by mineral matter. Heart Lake BSi is likely affected by wind-driven remobilization of sediment, as suggested by correlations among BSi, the North Pacific Index, and winter storminess. The results indicate relatively stormy conditions from 9.6 to 4.0 ka [thousands of years ago], followed by drying between 4.0 and 2.7 ka, with the driest conditions from 2.7 to 1.5 ka. The stormiest period was between AD 500 and 1200, then drying from 1150 to 1500 and more variable until 1850. This record of Holocene storminess fills a major gap at the center of action for North Pacific wintertime climate.

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