last glacial maximum

Last Glacial MaximumChapter 12Bao, Mario, Ariel, & Keiyro

12-1 Project CLIMAPCLIMAP (Climate Mapping and Predictions) Project began in early 1970s

First map of ice-age Earth released 1976

12-1 First CLIMAP Map

12-1 Project CLIMAPMajor Ice Sheets….-Laurentide ice sheet-Cordilleran ice sheet-Scandinavian ice sheet-Barents ice sheet

12-2 How Large Were the Ice Sheets?

CLIMAP reconstruction highly controversial due to:

1. The extent that ice reached2. Ice centered on marine ice sheets3. Thickness and height of ice sheets

12-3 Glacial DirtGlacial outwash: sediment deposits from glacial meltwater

12-3 WindWind reworks and carry deposits-Deposits can be

worldwide-Na+ and Cl- ions

(salt)

12-4 COHMAPCOHMAP (Cooperative Holocene Mapping Project) began in 1980s

Combined data-model approach to examine the last glacial maximum and subsequent changes to interglacial conditions.

12-4 COHMAP Approach1. Assemble records of changing conditions that drive climate-Over last 21,000 years

2. Ran model simulations of climate3. Climate data produced was tested against climate reconstructions

12-5 Pollen: A Climate IndicatorPrecipitation and temperature determine vegetation growth

Pollen is carried by wind, water, insects-Settles into mud and preserved

12-5 Pollen in a Lake Core-Spruce pollen-Oak pollen-Prairie pollen

12-6 Distribution of Spruce Pollen

12-6 Biome ModelsA model that simulates the vegetation that can exist in a region

12-7 Glacial Ice SheetsIce sheets affected atmospheric flow

Massive, icy plateaus blocked/redirected the flow of air

12-8 Northern Ice SheetsMost dramatic climate changes experienced by regions closest to ice sheets

12-8 Changes in North AmericaLakes once occupied deserts in SW U.S

Pacific NW was colder and drier

Climate due to jet stream’s influence

Glacial Lakes

12-8 Changes in EurasiaClimate was far harsher and colder

Less trees and vegetation

European Steppe

12-8 Europe Comparison

12-8 PermafrostPermafrost: permanently frozen soil and rocks due to the cold

Evidence of permafrost in Asia

12-9 Away from the Northern SheetsClimate changes less dramatic

More affected by CO2 and methane gas

ITCZ Biomass

12-9 Glacial TropicsOceans were 1°-2°C cooler

-Based off plankton fossils

Tropics too far away from ice sheets to be affected

-What caused cooling in the tropics?

12-10 Small Tropical CoolingCLIMAP reconstruction based on planktic fauna/flora in oceans

Evidence shows ocean temperatures cooled by an average of 1.5°C

12-10 AlkenonesAlkenones: organic molecules in plant plankton shells

Used in temperature reconstructions

12-11 Large Tropical Cooling The atmosphere cools 6.5°C for every kilometer

4°-6°C cooling shown from drop in ice line of tropical mountains

12-11 Large Tropical Cooling

12-12 Tropical CoolingCLIMAP estimated tropical cooling to be small

andCritics estimated tropical cooling to be large

Which side was right?

12-12 Medium-Small CoolingErrors of CLIMAP-Dissolved CaCO3

samples-Latitude and Plankton

adaptability

12-12 Medium-Small CoolingDiscrepancies between land and ocean temperature changes-Lowering of sea level-Greater land response to climate forcing

12-12 Medium-Small CoolingTemperature drop estimated to be 3°C

Models capture effects of greenhouse gases-Useful in forecasting future climate changes