Changes in Atmospheric Circulation and Ocean Ice Cover over the North Atlantic During the Last 41,000 Years

Abstract

High-resolution, continuous multivariate chemical records from a central Greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41,000 years. These chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to Greenland [defined here as the polar circulation index (PCI)] and in the extent of ocean ice cover. Massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in PCI. During stadials without discharge events, ocean ice cover appears to reach some common maximum level. The massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling.

Massive sand beds attributed to deposition by dense water cascades in the Bourcart canyon head, Gulf of Lions (northwestern Mediterranean Sea)

“…These fluctuations in sea-water temperature, that are linked by these authors to fluctuations of the polar circulation index (Mayewski et al, 1994), certainly have an impact on deep-water formation and cascading as observed nowadays.…”

Ice sheets and nitrogen

“…Having said that, nitrate is rare in having very similar average concentrations in the LGM and the Holocene; changes can be seen [49] at the glacial termination, but they are tiny compared with the vast factorial changes in all other chemical content. Nitrate does show clear annual cycles that are used as a component of the layer-counted dating of Greenland ice cores.…”

A transient flux model for convective infiltration: Forward and inverse solutions for chloride mass balance studies

“…In lieu of independent measures of chloride mass deposition history, a constant value of chloride mass deposition is typically used in CMB analysis with caveats regarding the failure of this assumption [e.g., Scanlon, 1991]. Ice core data indicates that atmospheric chloride deposition was lower over Greenland during the Holocene compared to that during the late Pleistocene [Mayewski et al, 1994]. Chloride in the atmosphere arises from sea salts; therefore major paleoclimatic shifts in prevailing wind patterns that occurred during glaciation on northern continents [Thompson et al, 1993] [1986] reported anion velocities that were double the velocity of water at a clay loam field site, while at a sandy soil site the water and anions had almost the same velocity.…”