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Southeast (SE) Asia is located in a transitional zone where hydroclimate is controlled by both the Indian and East Asian summer monsoon branches. Recent proxy-based studies and climate models suggest that the hydroclimate of SE Asia may be out of phase with neighboring regions, such as India and China. However, we lack sufficient proxy records to verify this postulation or to identify spatial and temporal variations. This study reconstructs both past temperatures and effective moisture in Central Vietnam during Marine Isotope Stage 3 (approximately 50,00 to 30,000 years BP) to determine how these two climate variables relate in the past. Terrestrial temperatures and precipitation are reconstructed using biomarkers (branched glycerol dialkyl glycerol tetraethers, brGDGT) and compound-specific isotope analyses (carbon and hydrogen-isotopic values of leaf wax n-acids, δ13Cwax, and δDwax) from a buried peat deposit in the Central Highlands of Vietnam. The brGDGTs-derived annual temperatures range from 22.9 to 26.2°C and show a warming trend coincident with a weakening of summer insolation. A coincident and gradual enrichment of δ13Cwax from 47 to 33 kyr BP suggests a transition from C3 to C4 vegetation dominance. Such a response could signal an overall decrease in precipitation or a shift in the seasonality of precipitation. The δDwax data, however, do not indicate an overall drying trend, which supports the idea that a shift in the seasonality of rainfall, along with higher annual temperatures, is driving the vegetation change. In addition, the δDwax records may exhibit a trend opposite to a site in Thailand. We argue that the isotopic variability in the precipitation of Central Vietnam reflects the shift in moisture sources along with the shift in seasonality. In this case, an increase in amount of precipitation derived from the South China Sea in winter months is marked by rain enriched in δ2H-which could also be interpreted as a decrease in precipitation. The increase in rainfall during winter monsoon months (e.g. winter) in the Central Highlands of Vietnam does not appear to reach Thailand. We recommend that the precipitation proxies should be applied with knowledge of regional climate context and argue that better geographic representation of monsoonal climates is necessary to fully understand and model this critical climate system.

Paleoclimate records from lakes of the southwestern USA have been limited by a lack of independent paleothermometers, resulting in conflicting characterizations of millennial-scale variability in temperature and moisture. Here a novel method called Brillouin thermometry is applied to halite-bearing dry intervals of the late Pleistocene/Holocene (45–0 ka) core record of Searles Lake, California. Halite from the sediment-water interface records lake bottom temperatures during dry, high salinity periods. Analysis of modern saline lakes of various chemistries, depths, climate zones, and mixing regimes shows that: 1) average bottom water temperature is approximately equal to mean annual air temperature, and 2) annual range of bottom water temperature is inversely proportional to lake depth. Brillouin temperatures for eight halite intervals 30.6 ka to 8.5 ka range from 11.8 ± 3.6 to 22.4 ± 3.2 °C. Bottom water temperature variability indicates paleolake depths of ~10 m during halite precipitation. Brillouin thermometric results are then assessed in comparison with two additional temperature proxy records from the same Searles Lake sediment core: 1) branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from wet mud intervals, and 2) thermodynamic constraints from evaporite minerals and mineral sequences. Temperatures from brGDGTs for mud intervals 44.7 ka to 3.6 ka range from 13.4 ± 2.8 to 23.9 ± 3.0 °C. Comparisons of Brillouin/brGDGT temperatures with predicted equilibrium temperatures of salt crystallization indicate intervals where seasonal temperature variability forced the dissolution and/or recrystallization of existing temperature-sensitive evaporites. The multiproxy temperature record of Searles Lake agrees with other regional records at glacial/interglacial timescales but displays a wider degree of millennial-scale variability, with temperatures during the last glacial ranging from 8.3 °C below modern mean annual temperatures to 3.8 °C above.

In this poster, I will present plans to complete a PlioMIP2 simulation at high resolution (HR) in the fully-coupled Community Earth System Model (CESM). This simulation is part of the NCAR Accelerated Scientific Discovery PaleoWeather project and also includes HR simulations of the Early Eocene Climatic Optimum, with CO2 reconstructed to be much higher than today’s, and the Last Glacial Maximum with much lower CO2. CESM is being configured with a resolution of 0.25° for the atmosphere and land, and 0.1° for the ocean and sea ice. This set of fully-coupled paleo-HR climate simulations for past greenhouse and icehouse climates will study the drivers that govern the characteristics of extreme weather events in both atmosphere and ocean under altered climate states. Potential applications include diagnosing changes in atmospheric synoptic features like mesoscale convective systems, tropical cyclones, monsoons, and atmospheric rivers, of coastal upwelling zones, and for their impacts on past regional precipitation patterns. In addition, the paleo-HR simulations will better resolve the landscape of topographies and coasts. Both are critical for accurate comparison with the paleoclimate record since most of the terrestrial and marine paleo-observations come from basins surrounded by mountains and near-shore locations. The paleo-HR simulations will complement the preindustrial, historical and RCP8.5 future simulations available from the iHESP project (https://ihesp.tamu.edu/), resulting in HR simulations to investigate the dynamics that connect past and future climate changes.

The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than present day. As such, study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model-model and model-data intercomparison of three early Paleogne time slices: latest Paleocene, Paleocene-Eocene thermal maximum and early Eocene climatic optimum. A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate atlas will be used to constrain and evaluate climate models for the three selected time intervals, and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.