Abstract

High resolution, downscaled climate model data are used in a wide variety of applications in environmental sciences. Here we present the CHELSA-TraCE21k downscaling algorithm to create global monthly climatologies for temperature and precipitation at 30 arcsec spatial resolution in 100 year time steps for the last 21,000 years. Paleo orography at high spatial resolution and at each timestep is created by combining high resolution information on glacial cover from current and Last Glacial Maximum (LGM) glacier databases with the interpolation of a dynamic ice sheet model (ICE6G) and a coupling to mean annual temperatures from CCSM3-TraCE21k. Based on the reconstructed paleo orography, mean annual temperature and precipitation was downscaled using the CHELSA V1.2 algorithm. The data were validated by comparisons with the glacial extent of the Laurentide ice shield based on expert delineations, proxy data from Greenland ice cores, historical climate data from meteorological stations, and a dynamic simulation of species a distribution throughout the Holocene. Validations show that CHELSA TraCE21k output creates a reasonable representation of the distribution of temperature and precipitation through time at a high spatial resolution, and simulations based on the data are capable of detecting effective LGM refugia of species.

Highlights

  • Since the Last Glacial Maximum (LGM), variation in climate has caused multiple changes of the Earth surface, including the rearrangement of species distributions, or even extinctions (Adams and Faure, 1997; Binney et al, 2017; Prentice et al, 1991; Velichko et al, 1997; Williams et al, 2004; Yu et al, 2010)

  • Paleo orography at high spatial resolution and at each timestep is created by combining high resolution information on glacial cover from current and Last Glacial Maximum (LGM) glacier databases with the interpolation of a dynamic ice sheet model (ICE6G) and a coupling to mean annual temperatures from Community Climate System Model version 3 (CCSM3)-TraCE21k

  • Validations show that CHELSA TraCE21k output creates a reasonable representation of the distribution of temperature and precipitation through time at a high spatial resolution, and simulations based on the data are capable of detecting effective LGM refugia of species

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Summary

Introduction

Since the Last Glacial Maximum (LGM), variation in climate has caused multiple changes of the Earth surface, including the rearrangement of species distributions, or even extinctions (Adams and Faure, 1997; Binney et al, 2017; Prentice et al, 1991; Velichko et al, 1997; Williams et al, 2004; Yu et al, 2010). This process uses the high-resolution information of current day climatologies, and adds an interpolated anomaly derived from a coarser-resolution GCM (Hunter and Meentemeyer, 2005; Willmott and Robeson, 40 1995) While this approach works rather well for short term time series where topography is relatively stable (Daly et al, 1997), it becomes difficult for longer time series where the dependence structure between variables (e.g. topography and climate) is dynamic (Maraun, 2013). The ocean model in CCSM3-TraCE21k uses the NCAR version of the Parallel Ocean Program (POP) with 25 vertical levels and the sea ice model is the NCAR Community Sea Ice Model (CSIM)

Observational climatology
Transient glacial extent simulations
Observational glacial extent at Last Glacial Maximum (LGM) 85
Observational current glacial extent
Methods
Paleo-orography
Temperature coupling
Precipitation estimation
Comparison with temperature proxies from Ice core data
Validation of glacier extent between 18kPB and 1kBP
Accuracy of the glacier extent between 18kPB and 1kBP 345
Conclusions

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