文摘
Here we review proxy records of intermediate water temperatures from sediment cores in the equatorial Pacific and northeastern Atlantic Oceans, spanning 10,000 years beyond the instrumental record. These records suggests that intermediate waters were 1.5–2 °C warmer during the Holocene Thermal Maximum than in the last century. Intermediate water masses cooled by 0.9 °C from the Medieval Climate Anomaly to the Little Ice Age. The records suggest that dynamic processes provide an efficient mechanism to amplify small changes in insolation into relatively large changes in OHC. Over long time periods the ocean's interior acts like a capacitor and builds up large (positive and negative) heat anomalies that can mitigate or amplify small radiative perturbations as seen in the Holocene trend and Common Era anomalies, respectively. Evidently the ocean's interior is more sensitive to small external forcings than the global surface ocean because of the high sensitivity of heat exchange in the high-latitudes to climate variations.