Twenty years ago, measurements on ice cores showed that the concentration of carbon dioxide in the atmosphere was lower during ice ages than it is today. As yet, there is no broadly accepted explanation for this difference. Current investigations focus on the ocean's 'biological pump', the sequestration of carbon in the ocean interior by the rain of organic carbon out of the surface ocean, and its effect on the burial of calcium carbonate in marine sediments. Some researchers surmise that the whole-ocean reservoir of algal nutrients was larger during glacial times, strengthening the biological pump at low latitudes, where these nutrients are currently limiting. Others propose that the biological pump was more efficient during glacial times because of more complete utilization of nutrients at high latitudes, where much of the nutrient supply currently goes unused. We present a version of the latter hypothesis that focuses on the open ocean surrounding Antarctica, involving both the biology and physics of that region.

https://faculty.washington.edu/battisti/589paleo2005/Papers/SigmanBoyle2000.pdf

Glacial/interglacial variations in atmospheric carbon dioxide

Variability of the North Atlantic Oscillation and the Tropical Atlantic dominate the climate of the North Atlantic sector, the underlying ocean and surrounding continents on interannual to decadal time scales. Here we review these phenomena, their climatic impacts and our present state of understanding of their underlying cause. Copyright © 2001 Royal Meteorological Society.

/pdf/north-atlantic-climate-variability-phenomena-impacts-and-1wk1sttha1.pdf

North atlantic climate variability: Phenomena, impacts and mechanisms

The meridional overturning circulation of the ocean plays a central role in the climate and its variability. This Review of recent studies emphasizes the importance of wind-driven upwelling in the Southern Ocean for global ocean circulation.

http://oceans.mit.edu/JohnMarshall/wp-content/uploads/2013/08/Closure-of-the-meridional-overturning_134.pdf

Closure of the meridional overturning circulation through Southern Ocean upwelling

[1] An idealized general circulation model is constructed of the ocean's deep circulation and CO2 system that explains some of the more puzzling features of glacial-interglacial CO2 cycles, including the tight correlation between atmospheric CO2 and Antarctic temperatures, the lead of Antarctic temperatures over CO2 at terminations, and the shift of the ocean's δ13C minimum from the North Pacific to the Atlantic sector of the Southern Ocean. These changes occur in the model during transitions between on and off states of the southern overturning circulation. We hypothesize that these transitions occur in nature through a positive feedback that involves the midlatitude westerly winds, the mean temperature of the atmosphere, and the overturning of southern deep water. Cold glacial climates seem to have equatorward shifted westerlies, which allow more respired CO2 to accumulate in the deep ocean. Warm climates like the present have poleward shifted westerlies that flush respired CO2 out of the deep ocean.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2005PA001154

Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages

The ocean circulation is a cause and consequence of fluid scale interactions ranging from millimeters to more than 10,000 km. Although the wind field produces a large energy input to the ocean, all but approximately 10% appears to be dissipated within about 100 m of the sea surface, rendering observations of the energy divergence necessary to maintain the full water-column flow difficult. Attention thus shifts to the physically different kinetic energy (KE) reservoirs of the circulation and their maintenance, dissipation, and possible influence on the very small scales representing irreversible molecular mixing. Oceanic KE is dominated by the geostrophic eddy field, and depending on the vertical structure (barotropic versus low-mode baroclinic), direct and inverse energy cascades are possible. The pathways toward dissipation of the dominant geostrophic eddy KE depend crucially on the direction of the cascade but are difficult to quantify because of serious observational difficulties for wavelengths shorte...

Ocean Circulation Kinetic Energy: Reservoirs, Sources, and Sinks

https://gfdl.noaa.gov/bibliography/related_files/jrt9502.pdf

B. Samuels

Papers

Effect of Drake Passage on the global thermohaline circulation