1584 / 2024-10-06 17:11:24

North Pacific deep circulation changes across the Mid-Brunhes Event

ODP Site 882,Mid-Brunhes Event,North Pacific,Deep water circulation

The 100-ka cycle of glacial-interglacial cycles has been the dominant feature of the Late Pleistocene climate change for a million years. Since ~430 ka, the amplitude of the 100-ka climate cycle has increased markedly, which is called Mid-Brunhes Event (MBE). The benthic oxygen isotope (δ¹⁸O) records show that the interglacials after MBE have been characterized by warmer climates and higher sea level.

Milankovitch theory suggests that the glacial-interglacial cycles are the result of the modulation of solar radiation by periodic changes in the Earth's orbital parameters, which are mainly composed of three parameters: eccentricity, obliquity and precession. The parameters of the Earth's orbital system did not undergo significant anomalous changes across the MBE, so it can be assumed that the increased amplitude of climate changes on glacial cycles after the MBE were the result of the internal feedbacks of the Earth system.

Meridional Overturning Circulation is an essential element of the ocean circulation and climate, and in modern times it is dominated by the Atlantic Meridional Overturning Circulation (AMOC) and the Southern Ocean Meridional Overturning Circulation (SOMOC). However, a comparable overturning circulation is absent in the North Pacific. There are a number of studies suggesting that there was also a strong Pacific Meridional Overturning Circulation (PMOC) in the North Pacific Ocean during the Last Glacial Maximum (LGM) ~20,000 years ago, which had played an important role in the climate evolution and heat transport during the glacial period. Some studies suggest that AMOC had influenced the sensitivity to interglacial CO₂ concentrations after MBE. As an essential element of the ocean circulation, PMOC may have had some similar influence on MBE.

We measured authigenic Uranium (aU) on the core samples from ODP site 882 (50.36^oN, 167.60^oE, water depth 3244 m) in the subarctic North Pacific. Based on this proxy record, we reconstructed the extent of the North Pacific deep-water ventilation across the MBE event that reveal the relationship of PMOC variation with global climate change across the MBE event.