Dartmouth Events

The early Eocene is punctuated by a series of rapid warming events, known as hyperthermals. The first among these, the Paleocene-Eocene Thermal Maximum, or PETM, has been argued to be one of the closest approximations to modern-day, anthropogenic warming in the geologic record. The PETM, and the subsequent hyperthermals of smaller magnitude, such as Eocene Thermal Maximum 2, or ETM2, can provide insight into how the climate system responds to different degrees of warming. In addition to temperature changes, these hyperthermals drove significant changes in regional precipitation patterns. This study seeks to better understand these changes, focusing on the mid-latitude North Atlantic coasts, utilizing a suite of techniques including high-resolution climate models and geochemical, sedimentological, and paleoecological proxies. Our models show a significant increase in the seasonality and extremes of precipitation in response to elevated CO2 levels, with significant regional variation in response to orbital forcing. In the western Mid-Atlantic, we find a dramatic weathering response to these precipitation changes, with an increase both in chemical alteration and physical transport of sediment. During ETM2, the climatic response was much more muted, with temperatures decreasing, a moderate increase in chemical weathering, and little response in the marine palynology, in stark contrast to studies of this time period in other regions. The disparate regional responses to various degrees and types of forcing highlights the importance accounting for climatic forcings apart from CO2 in paleoclimate studies such as orbital forcing and dynamic feedbacks.

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