WHICH ARE THE DRIVING MECHANISMS, AND WHICH ARE THE RESPONSES?
INSOLATION DRIVES THE ICE SHEETS, ICE SHEETS DRIVE TEMPERATURES
Ice Driven Responses: (1) Elevation of ice affects Atmospheric Circulation; (2) High albedo lowers temperatures; (3) Ice calving into oceans lowers water temperatures
Ice sheet volume and Sea surface temperatures track together during 1.5 to 1.2 million yrs ago, revealing 41,000 year cycle in earth's tilt. Evidence of ice sheets driving SST rather than insolation.
GCM Demonstrates differences in Atmospheric Circulation associated with Ice Sheets, compared with No Ice Sheets. See differences in Westerlies, Polar Jet Stream with Ice Sheet. Note also stronger winds with ice sheets -- stronger temperature gradients.
In pollen record, herbs correlate with cold, dry, periglacial conditions; trees equal warmer, moister, temperate conditions. These are downwind from influence of the ice sheets, which are driving air and sea surface temperatures.
Sea Surface temperature sensitivity test, modeled with GCM. Input is SST, output is Air Temperatures downwind of North Atlantic Ocean.
Evidence from Far East: Wind-blown LOESS deposits correlate with cold, dry conditions; Soil development indicates warmer, moister, more stable (less windy) conditions. How far does the influence (forcing) of the North American and Fennoscandian Ice Sheets reach?
Conclusion: Ice sheets respond to orbital variations; air temperatures, sea surface temperatures, atmospheric circulation, precipitation patterns all respond directly to ice volume. Ice sheets drive climate in the midlatitude Northern Hemisphere.
What about areas far from the Northern Hemisphere Ice influence?
