Highly Resolved Temperature and Carbon Cycle Dynamics in the Indian Ocean across the Mid-Pleistocene Transition
Abstract
The Mid-Pleistocene transition (MPT) is known as the most recent step change in orbital scale climate dynamics. Quaternary glacial-interglacial climate cycles lengthened their periodicity from 41 thousand year (ka) to quasi-100 ka, and switch from virtually sinusoidal to distinctly asymmetrical saw-tooth shaped cycles. The transition occurs without any notable change in the orbital parameters. This necessitates a change to Earth's internal feedback mechanisms, which may respond to a long-term decrease in atmospheric pCO2. The onset, duration and completion of the MPT are still subject to discussion. However, it is generally accepted that the climate system reorganisation occurred somewhere between 1200 ka and 600 ka, with a major event around 900 ka. The "900ka event" is evident in most sea surface temperature (SST) records suggesting a reorganisation of ocean surface conditions and is presumably linked to atmospheric and carbon cycle changes. So far, no clear conclusions can be drawn concerning the influence of long-term CO2 decline on sea surface conditions across the MPT and around the "900ka event". In this study, we attempt to explore the possible links between ocean surface dynamics and the carbon cycle by focusing on the scarcely sampled Indian Ocean. Here, we present highly resolved elemental and isotope records from the recently drilled IODP site U1476 located in the Mozambique Channel. The core is located at intermediate depth (2166m) and exhibits exceptional preservation. It is therefore ideal for investigating sea surface conditions using combined trace metal and isotope analyses. We mainly collected high resolution (1 sample per 1000 years) Mg/Ca and δ18O to derive surface temperatures, and δ13C, B/Ca and low resolution boron isotope measurements as carbon cycle proxies across 850 ka - 1150 ka. Much of the mean CO2 decline over the MPT was associated with a glacial drawdown towards longer and more intense cold periods. We aim to interrogate both long-term changes to global CO2 levels and local response to surficial carbon reservoirs in this understudied basin, and gain an insight into the mechanisms that influenced the evolution of glacial maxima across the MPT.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP23F1555N
- Keywords:
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- 4926 Glacial;
- PALEOCEANOGRAPHYDE: 4936 Interglacial;
- PALEOCEANOGRAPHYDE: 4946 Milankovitch theory;
- PALEOCEANOGRAPHY