Temporal and geographic extent of the late Holocene dry period in the central Great Basin, USA

Abstract

We provide evidence from pollen and radiocarbon dating of wet meadow sediments for the presence of multi-centennial drought, termed the Late Holocene Dry Period (LHDP), in the central Great Basin between 3100 and 1800 cal yr BP. We examine four sites along a south to north transect between 39° N and 42° N latitude, spanning the boundary of the anti-phasing dipole pattern of precipitation associated with ENSO. The LHDP conforms to the dipole pattern but contains three different phases, an initial 900-year dry period, followed by 200 years of wetter climate and then another 200 years of extreme drought. The dipole boundary appears to have shifted to a new semi-stable position with each period. Between 3100 and 2200 cal yr BP, the boundary seems to conform to the 40° N parallel across central Nevada, and trending to 42° N in northwest Nevada. Between 2200 and 2000 cal yr BP the boundary shifted south of 40° N, when all sites predominantly record wet conditions. Between 2000 and 1800 cal yr BP the boundary shifts north to ∼41° N, representing the driest phase which was widespread across central Nevada. A review of lake levels, tree-rings, and submerged stumps suggest that the drought between 2000 and 1800 cal yr BP was of greater magnitude than that recorded during the MCA megadrought. We do not yet have sufficient information to establish a cause for megadroughts, however it is important to note that the climate system periodically locks into a pattern with a consistently northward shifted storm track that persists for multiple decades to centuries, bringing persistent drought to the American Southwest. Indigenous human societies adapted to severe droughts through a variety of responses, suggesting a pattern of resilience and mobility in response to recurring climate change across the Great Basin.