Prolonged wet period in the southwestern United States through the Younger Dryas

Abstract

The Younger Dryas was one of the more dramatic climatic transitions ever recorded. How these types of climatic shifts are expressed in continental interiors is of primary scientific interest and of vital societal concern. Here we present a speleothem-based absolutely dated record (using uranium-series data) of climate change for the southwestern United States from growth chronology of multiple speleothems. The stalagmite growth represents the onset of wetter climate (12,500 yr B.P.) soon after the start of the Younger Dryas; the wetter climate persisted a millennium beyond the termination of the Younger Dryas. This wet cycle is likely related to a more southern positioning of the polar jet stream in response to cooler Northern Hemisphere climate. The end of the wet period coincides with the peak of the Holocene summer insolation maximum ca. 10,500 yr B.P. The Å llerød (prior to the Younger Dryas), which corresponds to Clovis occupation in the southwestern United States, was drier in comparison and seems in line with a climatic contribution to megafauna extinction.

The Holocene history of the North American Monsoon: ‘known knowns’ and ‘known unknowns’ in understanding its spatial and temporal complexity

“…Asmerom et al, 2010). Similar conditions apparently occurred during the full glacial (Benson et al, 1990;Bradbury et al, 2001;Polyak et al, 2004;Lachniet et al, 2014). This southward displacement of the jet stream has been supported by some climate modelling (see below).…”

Integration of ice‐core, marine and terrestrial records for the Australian Last Glacial Maximum and Termination: a contribution from the OZ INTIMATE group

“…Further afield, speleothem growth in southwestern USA indicates a sustained period of wet conditions between 12.4 and 11 cal. ka BP, consistent with El Niñ o disruption of the California Current (Polyak et al, 2004). It is possible that longterm changes in ENSO activity may have played an important role in regional climate change during the end of the Last Termination and beginning of the Holocene, though dating and quantification needs to be significantly improved.…”

Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

“…h Before the installation of river control structures (i.e., preindustrial); all other values (including those on the same line) are modern unless indicated. i Before modern water withdrawals (i.e., preindustrial); these values are estimated based on the work of Gates et al (2000) for the Rio Grande and Prairie and Callejo (2005) and Nowak (2011) for the Colorado River at Imperial Dam, which was summed with inputs from the Gila River (US Bureau of Reclamation, 1952); see Cohen et al (2001) for an earlier calculation of natural discharge to the Colorado River delta and Schmidt et al (2010) for a review of the 20th century human-river interaction that necessitated my approximation here. Modern values of water and sediment discharge are from Milliman and Farnsworth (2011).…”

“…These cool, wet periods are marked by high pluvial lake levels (e.g., Currey et al, 1990;Matsubara and Howard, 2009;McGee et al, 2012;Oviatt, 2015), mountain glacier advances prior to the onset of the Bølling-Allerød (e.g., Owen et al, 2003;Guido et al, 2007;Orme, 2008;Refsnider et al, 2008Refsnider et al, , 2009Brugger, 2010), increased landsliding in the Rio Grande basin between ∼ 21.2 and ∼ 14.5 ka (Reneau and Dethier, 1996), deposition of valley fills in the Colorado River (Pederson et al, 2013), and speleothem growth (e.g., Polyak et al, 2004;Oster and Kelley, 2016). The warmer Bølling-Allerød and Holocene correspond to records of mountain glacier retreat (Guido et al, 2007;Laabs et al, 2013;Munroe and Laabs, 2013) and strath terrace formation due to river incision (Anders et al, 2005;Cook et al, 2009).…”