Wednesday, September 18, 2013

New paper finds drought in the US Great Basin was much more extreme in the past

A paper published today in Quaternary Science Reviews finds a severe drought affected the US central Great Basin for almost one thousand years between 2800 and 1850 years ago. According to the authors, this drought was "the longest persistent dry period within the late Holocene." The paper shows modern precipitation levels are not unusually wet or dry, or unprecedented in comparison to the past 8,000 years. The paper adds to hundreds of other peer reviewed publications demonstrating that there is nothing unprecedented, unusual, or unnatural about modern day precipitation, drought, or extreme weather. 


Proxy for precipitation shown in 2nd graph from top. Horizontal axis is thousands of years before the present. Red shaded area shows the extended drought between 2800-1850 years ago.

The Late Holocene Dry Period: multiproxy evidence for an extended drought between 2800 and 1850 cal yr BP across the central Great Basin, USA

  • a Department of Geography, University of Nevada, Reno, NV 89557, USA
  • b Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA
  • c Dipartimento DAFNE, Universit√† degli Studi della Tuscia, Viterbo 01100, Italy
  • d Volcano Science Center, U.S. Geological Survey, Menlo Park, CA 94025, USA

Highlights

A persistent drought, ∼2800–1800 cal yr BP, occurred in the Great Basin, U.S.A.
We refer to this multi-centennial drought as the Late Holocene Dry Period.
Comparison with other records suggests that this dry period was regional in extent.
This is the longest persistent dry period within the late Holocene.

Abstract

Evidence of a multi-centennial scale dry period between ∼2800 and 1850 cal yr BP is documented by pollen, mollusks, diatoms, and sediment in spring sediments from Stonehouse Meadow in Spring Valley, eastern central Nevada, U.S. We refer to this period as the Late Holocene Dry Period. Based on sediment recovered, Stonehouse Meadow was either absent or severely restricted in size at ∼8000 cal yr BP. Beginning ∼7500 cal yr BP, the meadow became established and persisted to ∼3000 cal yr BP when it began to dry. Comparison of the timing of this late Holocene drought record to multiple records extending from the eastern Sierra Nevada across the central Great Basin to the Great Salt Lake support the interpretation that this dry period was regional. The beginning and ending dates vary among sites, but all sites record multiple centuries of dry climate between 2500 and 1900 cal yr BP. This duration makes it the longest persistent dry period within the late Holocene. In contrast, sites in the northern Great Basin record either no clear evidence of drought, or have wetter than average climate during this period, suggesting that the northern boundary between wet and dry climates may have been between about 40° and 42° N latitude. This dry in the southwest and wet in the northwest precipitation pattern across the Great Basin is supported by large-scale spatial climate pattern hypotheses involving ENSO, PDO, AMO, and the position of the Aleutian Low and North Pacific High, particularly during winter.

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