Million-year-old Arctic sedimentary record sheds light on climate mystery, researchers find

The new research, led by the University of Massachusetts Amherst and published recently in the journal Climate of the Past, is the first to provide a continuous look at a shift in climate, called the Mid-Pleistocene Transition, that has puzzled scientists. The first author of the paper was a graduate student at the University at Buffalo, and he was part of a team that included world- renowned climate scientists.

The Mid-Pleistocene Transition, or MPT, happened around 1.2 million years ago. Every 40,000 years or so, ice ages had previously occurred. The time between ice ages doubled to every 100,000 years in a relatively short window of geological time.

There are a lot of barriers to understanding the MPT. The oldest ice core is 130,000 years old. As ice ages have come and gone, the ice sheets have acted like enormous bulldozers, removing much of the exposed land down to the bedrock.

There is a place in far northeastern Russia that has never been covered by glaciers. This is where the world- renowned polar scientist, Julie Brigham-Grette, professor of geosciences at UMass Amherst and one of the paper's co-authors, comes in.

In 2009, a team of scientists led by Brigham-Grette traveled to Lake Elgytgyn, where they drilled a 685.5 meter core, representing the last 3.6 million years of Earth's history. The portion of the MPT that was used by Lindberg and his co-authors was used to look for specific markers that could help them determine temperature and vegetation. For the first time, they were able to reconstruct the conditions in the north during the MPT.

The team did not solve the mystery of the MPT, but they did make a few surprising discoveries. The records at Lake Elgytgyn show only moderate warmth, even though the interglacial period known as MIS 31 is widely recognized as having been warm. Three other interglacial periods, MIS 21, 27 and 29 were as warm or warmer. The research shows a long-term drying trend.

Casta says that this couldn't have been done without Lindberg's enthusiasm. Kurt did a great job with this project.

More information: Kurt R. Lindberg et al, Biomarker Proxy Records of Arctic Climate Change During the Mid-Pleistocene Transition from Lake El'gygytgyn (Far East Russia), Climate of the Past (2021). DOI: 10.5194/cp-2021-66 Journal information: Climate of the Past Citation: Million-year-old Arctic sedimentary record sheds light on climate mystery, researchers find (2022, March 30) retrieved 31 March 2022 from https://phys.org/news/2022-03-million-year-old-arctic-sedimentary-climate-mystery.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.