Comparing Precipitation Seasonality During the Last Deglaciation from Speleothem Records and Isotope-enabled Model Simulations
Abstract
Speleothem records provide a unique opportunity to synthesize estimates of the stable isotope signature of paleo-precipitation across a broad spatiotemporal range. Combining speleothem records with isotope-enabled climate models supports not only the reconstruction of past changes in atmospheric circulation, temperature, and precipitation but also the investigation of how these changes occurred and are recorded in paleoclimate archives. Here we present initial results from water isotope-enabled model simulations conducted with the Community Earth System Model (iCESM1) compared to speleothem records of climate change in North and Central America. Simulations at key time slices from the Last Glacial Maximum (LGM) to the present were branched from the transient iTraCE experiments. Drawing upon the recently published Speleothem Isotopes Synthesis and Analysis database (SISAL), we compare estimates of precipitation δ18O based on speleothem records from North and Central American to our model outputs. Following a recently published approach for comparing speleothem and climate model data [1], site-specific speleothem-based estimates of paleo-precipitation are computed from average speleothem δ18O values for each time period and the average annual temperature extracted from the model runs using an empirical speleothem-based isotope fractionation factor [2]. Using this approach, we find generally good agreement between proxy and model-based estimates of paleo-precipitation δ18O. However, the model-data agreement is generally stronger at most sites for season-specific model estimates of precipitation δ18O rather than annually-averaged estimates. Further, the season of closest agreement between model and proxy estimates varies between time slices. This suggests that isotope-based model-proxy comparisons may assist in unraveling past changes in precipitation seasonality and contribute to our understanding of seasonal bias in speleothem proxy records.
[1] Comas-Bru et al., (2019) Clim. Past Discuss, doi.org/10.5194/cp-2019-25. [2] Tremaine et al., (2011) Geochim. Cosmochim. Acta, doi.org/j.gca.2011.06.005.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP23B..02O
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGE;
- 4943 Paleolimnology;
- LIMNOLOGY;
- 4914 Continental climate records;
- PALEOCEANOGRAPHY;
- 4954 Sea surface temperature;
- PALEOCEANOGRAPHY