A 3.6 Ma branched GDGT temperature reconstruction from Lake El'gygytgyn, Far East Russia
Abstract
Little is known about the regional response of the high Arctic to past climate variability prior to ~100 ka. In 2009, a drill core spanning the past 3.6 Ma was recovered from Lake El'gygytgyn (LE), the largest and oldest unglaciated Arctic lake basin. Determining the magnitude of past continental temperature variability is especially relevant to understanding the mechanisms and feedbacks contributing to Arctic amplification. Here we present a Plio-Pleistocene Arctic temperature record based on ~2,200 branched glycerol dialkyl glycerol tetraether (brGDGT) samples, with an average sampling resolution of ~2,000 years. Throughout the entire record, we find that insolation is a main control on arctic temperature variability with strong 40 and 23 kyr signals present throughout the Pleistocene. Interestingly, a 40-kyr signal is also present during the Pliocene but is not expressed as robustly due to several coring gaps. This suggests during the Pliocene, the Arctic was sensitive to both summer insolation intensity and summer duration. Other major features noted in the brGDGT record include: 1) increasing glacial-interglacial variability at ~2.7 Ma, coincident with the intensification of northern hemisphere glaciation, 2) no major changes in temperature trends during the mid-Pleistocene transition (MPT), and 3) a strong signal of the Mid-Brunhes Event (MBE). Although no major temperature trends occur during the MPT, it is notable that sediment Facies C, a unique facies consisting of red laminations and interpreted as representing super interglacial conditions (warm and wet), only appears twice since the MPT but is present more regularly in older parts of the record. Overall, the previously identified super-interglacial intervals coincide with higher brGDGT-inferred temperatures but many other warm intervals exist when Facies C is not present. Pre- and post-MBE differences, expressed as changes in the both mean value and amplitude of numerous LE proxy records, may be attributed to shifts in atmospheric circulation related to North Pacific stratification and warming associated with changes in Antarctic Bottom Water production. Similarities in the timing of warm intervals noted in Antarctica and LE support previously proposed teleconnections between Antarctica and the Arctic.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP33A..02D
- Keywords:
-
- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES