A model-data comparison of the hydrological response to Miocene warmth: leveraging the MioMIP1 opportunistic multi-model ensemble
Abstract
The Middle Miocene Climatic Optimum (16.75-14.5 Ma) represents a period of amplified global warmth. It illustrates a potential future scenario of the Earth system as human activity continues to increase greenhouse gas concentrations. The availability of paleoclimate proxies such as fossil plant data gives critical information on the hydroclimate condition of the Miocene (20.03-5.33 Ma), while Earth system model simulations of the Miocene can give multiple realizations of the global climate and can serve as a tool to evaluate climate proxy signals. However, hydroclimate comparisons between Miocene proxies and paleoclimate simulations are limited. A recent opportunistic Miocene Model Intercomparison Project (MioMIP1) focused on the data-model comparison of global and regional temperature and radiative energy balance. Here we build on this effort by analyzing the hydrological cycle response to Miocene forcings across the MioMIP1 simulations and providing a comparison against available precipitation reconstructions.
This work analyzes early-to-middle and middle-to-late Miocene simulations with CO2 concentrations ranging from 200 to 850 ppm to evaluate precipitation data-model agreement and highlight mechanisms that control precipitation distribution. We show that annual-mean precipitation rates are underestimated by the MioMIP1 ensembles, especially against records found at high latitudes. While the data-model mismatch with respect to temperature proxies generally declines with increasing CO2concentrations, the same cannot be said for the precipitation comparison, which yields a similar bias for both the low and high CO2 ensembles (~350 mm). This is due to regional forcings and seasonality resulting in a higher degree of heterogeneity in precipitation fields. For example, simulations that used higher Tibetan topographic elevation yield better data-model agreement suggesting differences in topography input are a source of discrepancy. Analysis of GCM-derived winter precipitation yields a better comparison with higher latitude proxies and indicates the need to better constrain seasonality in precipitation records. This study highlights the challenges related to regional forcing uncertainty and seasonality when performing a proxy-model comparison of the Miocene hydrological cycle.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMPP35B..03A