Douglas L. Love
No one cause can be found for the observation that glacial pCO2 was 80-90 μatm lower than in
interglacial periods. Some ideas that have been presented include:
- Ocean circulation models are more diffusive than the modern ocean, underestimating the
pCO2 sensitivity to the biological pump
- The Redfield N/P number was different in glacial time.
- Double the inventory of H4SiO4 in the ocean, raising the pH of the deep ocean.
- Cooling in the Southern Ocean at the same time as CO2 is falling is considered as a cause,
but is nowhere strong enough to cause the observed drop.
- Increased dust flux in the glacials caused more nitrogen fixation, which allowed a greater
CO2 drawdown in surface waters.
- Long residence time of NO3 in ocean explains how CO2 can continue to increase after the
dust flux ix zero, and means productivity changes can be global.
- The Glacial Burial Hypothesis
- Glacial bottom waters were possibly much more saline, May have an unsuspected large
- The glacial deep ocean was more stably stratified than it is today. Geothermal heat would
have slowly warmed it from below, destabilizing it, like a discharging capacitor. This injects
salt into the upper North Atlantic, kick-starting thermohaline circulation. Reinvigorated
circulation warms up Greenland and the North Atlantic.
- Overturnings occur in nature through a positive feedback that involves mid-latitude westerly
- species change in phytoplankton produced only 20-25% Carbonate plus Opal during ice ages
vs 90% now.
- Carbon Storage on exposed continental shelves during the glacial-interglacial transition
- The climate instability of glacial times probably resulted from abrupt switches in ocean