Speaker/Affiliation: Isabel P. Montañez, UC Davis
Title: A stalagmite perspective on CA’s hydroclimate response to Heinrich Stadials
When: Wednesday, February 4 12:00pm PST
Location: EMS B214
Abstract: Heinrich Stadials (HS) of the last glacial period and deglaciation were characterized by abrupt North Atlantic cooling, massive ice discharge, and atmospheric CO₂ and CH4 fluctuations. Consequent major changes in Atlantic Meridional Overturning Circulation and atmospheric regime shifts led to decadal- to millennial-scale changes in continental hydroclimate across both hemispheres. How and by what mechanisms the regional hydroclimate in the western U.S. responded to these high-latitude climate events, remains poorly resolved given that existing proxy records from this region lack the necessary temporal resolution to resolve phasing relationships with proxy records from distal climate regimes. In this talk, I will present stalagmite-based proxy records from CA that archive two Heinrich stadials (HS 1 and HS 4) to illustrate how the hydroclimate in this highly seasonal region — susceptible to drought and extreme precipitation events — responded to centennial to millennial-scale climate forcings through strong atmospheric and oceanic teleconnections to the North Atlantic. These hydroclimate reconstructions, based on O, C, H, Sr, and Ca isotope and trace element time series reveal latitudinal variability in effective moisture through CA with everwet conditions proximal to the precipitation dipole and a multi-phased response to the south. For HS 4, the multi-phased hydroclimate response is consistent with changes in the intensity of the East Asian Summer Monsoon observed in stalagmites from southeastern China. Centennial cycles and sub-centennial variability is superimposed on the longer-term changes. Moreover, temporal trends in the molecular proxy records coupled with trends in d-excess estimated from fluid-inclusion isotopic compositions, indicate that in CA’s moisture-limited regime, periods of reduced effective moisture provided conditions conducive to elevated wildfire activity. Collectively, the CA stalagmite records provide a new multi-year resolution perspective on the hydroclimate response to Heinrich Stadials that improves our understanding of how ocean–atmosphere mechanisms transmitted high-latitude climate signals across the hemispheres during past periods of millennial-scale climate change.
