Hiner, Christine A. and Kirby, Matthew E. and Bonuso, Nicole and Patterson, William P. and Palermo, Jennifer and Silveira, Emily

Late Holocene hydroclimatic variability linked to Pacific forcing: evidence from Abbott Lake, coastal central California

Late holocene climate changes in eastern North America estimated from pollen data

Asmerom Y, Polyak VJ, Rasmussen JBT, Burns SJ, Lachniet M.

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 13501650, 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.

Asmerom, Y. and Polyak, V. J. and Rasmussen, J. B. T. and Burns, S. J. and Lachniet, M.

Proceedings of the National Academy of Sciences

Multidecadal to multicentury scale collapses of Northern Hemisphere monsoons over the past millennium

Note added by NAm2k hydroclimate authors: Authors focus on band thickness rather than d13C

greater regional precipitation equates to more vegetation, more productive soils, and more soil CO2 production, all producing more negative Î´13C values