Climate Evolution Across the Mid-Brunhes Transition

Abstract:

The Mid-Brunhes Transition (MBT, ~430 ka) has been defined as a transition to a climate system with higher amplitude glacial and interglacial periods suggesting a major shift in the 100-kyr cycle at a time of minimal orbital forcing. To evaluate the expression of the MBT signal in the climate system, we analyze 15 sea-surface temperature, 18 benthic ∂¹³C, and 8 dust records using principal component and spectral analyses and variance estimation methods. Our results identify a significant difference in the variance of the first principal components of the SST and dust across the MBT with a punctuation of the 100-kyr frequency centered around ~400 ka. The first principal component of SST is strongly correlated with the atmospheric CO₂ record from EPICA Dome C (r² = 0.80). The first principal component of dust is inversely correlated with CO₂ (r² = -0.73) and the first principal component of SST (r² = -0.69). The ∂¹³C records of each major ocean basin were analyzed separately, with the Atlantic and Pacific records both exhibiting a decrease in variance across the MBT boundary. The first principal component of the ∂¹³C record from the Atlantic shows a large excursion during MIS 13 (500-530 ka), and could suggest a change in the Atlantic Meridional Overturning Circulation at this time. High correlation (r² = 0.92) between the first principal component of the Pacific and the second principal component of the Atlantic suggests a reservoir signal that also records high values during MIS 13.