title: Multidecadal to multicentury scale collapses of Northern Hemisphere monsoons over the past millennium.
abstract: Late Holocene climate in western North America was punctuated by periods of extended aridity called megadroughts. These droughts have been linked to cool eastern tropical Pacific sea surface temperatures (SSTs). Here, we show both short-term and long-term climate variability over the last 1,500 y from annual band thickness and stable isotope speleothem data. Several megadroughts are evident, including a multicentury one, AD 1350-1650, herein referred to as Super Drought, which corresponds to the coldest period of the Little Ice Age. Synchronicity between southwestern North American, Chinese, and West African monsoon precipitation suggests the megadroughts were hemispheric in scale. Northern Hemisphere monsoon strength over the last millennium is positively correlated with Northern Hemisphere temperature and North Atlantic SST. The megadroughts are associated with cooler than average SST and Northern Hemisphere temperatures. Furthermore, the megadroughts, including the Super Drought, coincide with solar insolation minima, suggesting that solar forcing of sea surface and atmospheric temperatures may generate variations in the strength of Northern Hemisphere monsoons. Our findings seem to suggest stronger (wetter) Northern Hemisphere monsoons with increased warming.
authors.affiliation: Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA. asmerom@unm.edu
authors.forename: Yemane
authors.initials: Y
authors.lastname: Asmerom
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Polyak
authors.forename: Jessica B T
authors.initials: JB
authors.lastname: Rasmussen
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Burns
authors.forename: Matthew
authors.initials: M
authors.lastname: Lachniet
mesh_terms: D002247:Carbon Isotopes; D002980:Climate; D055867:Cyclonic Storms; D055864:Droughts; D005843:Geography; D057232:Global Warming; D009656:North America; D009792:Oceans and Seas; D010103:Oxygen Isotopes; D011891:Rain; D012621:Seasons; D013696:Temperature; D013997:Time Factors; D014872:Water Movements
chemical_list: D002247:Carbon Isotopes; D010103:Oxygen Isotopes
keywords: climate change; global warming; uranium series