Reconstructing Past Climates K Gajewski Department of Geography, Environment and Geomatics University of Ottawa August 2016

What we are trying to do: KR02 Western Victoria Island Peros and Gajewski. 2008. QSR

Reconstruction of past climates from pollen assemblages Datasets needed Spatial series of modern ‘calibration” data Spatial series of climate (at each site Methodology Analogue method Regression approach Results Time series Maps Regional averages

Reconstruction of past climates from pollen assemblages Datasets needed Spatial series of modern ‘calibration” data Spatial series of climate (at each site Methodology Analogue method Regression approach Results Time series Maps Regional averages

Microfossil Samples 14-C date “Surface Sample”

Whitmore et al. 2005. QSR

Total Annual Precipitation (mm) Mean July Temp (oC) Total Annual Precipitation (mm) Anderson et al. 1991. J Biogeography

Reconstruction of past climates from pollen assemblages Datasets needed Spatial series of modern ‘calibration” data Spatial series of climate (at each site Methodology Analogue method Regression approach Results Time series Maps Regional averages

Methodology Dataset 1: core(s) – pollen assemblages Dataset 2a: “modern” – pollen assemblages Dataset 2b: modern climate at every modern pollen sample Step 1: Calibrate modern pollen to modern climate Step 2: Apply transfer function down-core Alternative: Find closest analogue (statistical distance) of modern sample to every fossil sample; assign modern climate from that point to fossil point

Reconstruction of past climates from pollen assemblages Datasets needed Spatial series of modern ‘calibration” data Spatial series of climate (at each site Methodology Analogue method Regression approach Results Time series Maps Regional averages

Example: Reconstruction of a time series at one site KR02 Western Victoria Island Peros and Gajewski. 2008. QSR

Comparison of reconstruction to instrumental data Keizer and Gajewski. 2015. RPP

Keizer and Gajewski. 2015. RPP

Example: map of climate at 6ka

Sawada et al., 2004. QSR Fig. 10. (a) 0 ka modern July temperature reconstructed at the 545 fossil sample sites. (b) 6 ka July temperature reconstructed at the 545 fossil pollen sample sites from the MAT, (c) July temperature anomalies (6–0 ka). (d) CCCma AGCM2 July temperature anomalies at model resolution.

Comparison to climate model Sawada et al., 2004. QSR

Example: Regional Average Holocene Viau et al. 2006. J Geophysical Research 111, D09102,

Gajewski. 2008 Prog Phys Geogr 32:

Millennial-scale climate variability in the Holocene Figure 2. (a) North American mean July temperature anomaly for the past 14,000 cal. yr. BP. (b) Mean July temperature anomaly of the past 10,000 cal. yr. BP. Roman numerals identify four part division of the Holocene. (c) Spectral analysis on detrended temperature anomaly curve of the last 14,000 cal. yr. BP. Viau et al. 2005

For period of overlap, pollen based North American reconstruction compares well to tree-ring based Northern Hemisphere Viau et al. 2005. J Geophysical Research 111, D09102,