Summary

Views on what causes ocean-glacier interactions during D-O cycles and Heinrich events fall into two camps. One is glacier-centred and assumes that free oscillations in glaciers and ice sheets cause recurring discharges of icebergs into the ocean. The iceberg

Calendar age in kyrs

Figure 24.7 Model results from Braun et al. (2005) using the CLIMBER-2 model forced with the DeVries solar cycle (210yr) and the Gleissberg solar cycle (88 yr) under glacial boundary conditions. Vertical dashed lines demark an exact 1470-yr pacing. Even though weak, the solar forcing in the model produces ocean surface-temperature anomalies of several degrees C with an exact pacing of 1470 yr.

Calendar age in kyrs

Figure 24.7 Model results from Braun et al. (2005) using the CLIMBER-2 model forced with the DeVries solar cycle (210yr) and the Gleissberg solar cycle (88 yr) under glacial boundary conditions. Vertical dashed lines demark an exact 1470-yr pacing. Even though weak, the solar forcing in the model produces ocean surface-temperature anomalies of several degrees C with an exact pacing of 1470 yr.

freshwater injections force recurring changes in the North Atlantic's deep-water circulation that in turn produce a series of robust abrupt climate changes with a global or nearly global footprint. The other is climate-centred and assumes that a climate mechanism of unknown origin forces increases in iceberg discharge either through direct effects on glacier mass balance or through changes in the North Atlantic deep circulation. In this case the glacier activity and its effects on NADW production operate as a non-linear positive feed-back that amplifies the climate signal and transmits a series of abrupt climate shifts well beyond the North Atlantic region. Both views have been criticized and neither can account for the striking 1500-year pacing of the D-O cycles and the presence of similar cycles in the Holocene when the large glaciers and ice sheets were absent.

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