Orbital Forcing of Western North American Hydroclimate during the Early Eocene Greenhouse
Abstract
Geological records from past greenhouse climate periods are critical to understanding warm climate system dynamics and can provide valuable insights into future climate system behavior in a warming world. The Early Eocene Climatic Optimum (EECO; 53-50 Ma) is the Earths most recent episode of greenhouse climate conditions and is associated with the warmest sustained temperatures of the Cenozoic. While the EECO has been the focus of decades of intense academic study, the behavior of the hydrologic cycle during this warm period remains one of the least constrained elements of its paleoclimate, despite its potential influence on regional climate, biology, and geology on the continents. Here we present a new high-resolution leaf wax D record from the lacustrine Wilkins Peak Member of the Green River Formation in Wyoming, one of the richest and best-dated terrestrial sedimentary archives of this climatically significant time period, in order to investigate hydroclimate variability in western North America during the EECO. Our results show decameter-scale Dwax variations of up to 50 at a temporal scale consistent with the ~100 ky short eccentricity cycle. To decipher the drivers of changes in precipitation and precipitation isotopes, we performed climate-isotope simulations using the water isotope-enabled Community Earth System Model (iCESM) across a range of orbital parameters. Model simulations suggest that high eccentricity is associated with an enhanced seasonal cycle in precipitation and isotopes, amplifying the winter storm track as well as spring and summer precipitation associated with Gulf moisture and a proto-North American monsoon, respectively. Thus, the large amplitude of Dwax observed at the Green River Formation likely reflects orbitally-driven shifts in the seasonality of precipitation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMPP13A..03W