1. The Surface of the Ice-Age Earth
Quantitative geologic evidence is used to reconstruct boundary conditions for the climate 18,000 years ago.
CLIMAP Project Members, 1973
(Climate: Long-range Investigation, Mapping, and Prediction)
Presented by Greg Hammond
December 2, 2009

2. CLIMAP
Objective: to study the history of global climate, beginning with a model of February 18,000 ka (August was modeled in 1981) and establish boundary conditions for:
Continent geography
Ice and land albedo
Extent and elevation of permanent ice
Sea-Surface temperature patterns

3. Boundary Conditions Geography
85 m sea level drop estimated from dated submerged terraces and on undated wave-cut notches at similar depths.
Small errors in sea level not considered significant with a model grid with km spacing.
Land Albedo
Pollen, snow line, and sedimentary records used to determine paleo-ground cover.
Modern analogous ground albedo used for model.
Ice Sheets
Ice sheet extent determined by a survey of literature supplemented with field work

4. CLIMAP Ice Extent and Vegetation Distribution

5. Snow/Ice
Desert
Loess
Grassland
Vegetated
Water

6. Sea-Surface Temperature
Boundary Conditions
Sea-Surface Temperature
Analysis of assemblages of foraminifera, coccoliths, and radiolara can be related to temperature based on modern analogues. Coccoliths preferred because they live in the euphotic zone, and thus most directly reflect surface temperature.
Oxygen-18 isotope data used to correlate carbonate remains with ice volume.
Carbon-14 dating applicable for some cases as dating control.
Ice sheet extent also based on biological records. Clays deposited by basal melting of ice sheets inhibit diatom growth, making an absence of diatoms an indicator of extent.

7. Sea-Surface Temperature: Difference between CLIMAP and modern values

8. CLIMAP Model of Sea-Surface Temperature, 18,000 ka

9. Results
The southern hemisphere was dominated by sea ice, the northern by a land-dominated combination .
Changes in sea-surface temperature distribution may have reduced and/or relocated currents.
Ice insulation may have inhibited thermohaline currents.
Altered currents may have thermally isolated certain areas.
Increased permanent snow/ice cover and less dense vegetation increased global albedo.

10. Atmospheric Response to Modified CLIMAP Ocean Boundary Conditions during the Last Glacial Maximum
Toracina, E, et al, 2002

12. Problems with the original CLIMAP model
CLIMAP suggests possible warming in the tropics. No other study has replicated this and instead suggest cooling of 1-8°C.
Overall average global sea-surface temperature modeled 1-2°C warmer than recent studies.
Not all northern seas would be ice bound—seasonal melting is likely. This would change circulation patterns.
Estimated sea-level drop too small.