Preprints
https://doi.org/10.5194/egusphere-2023-1960
https://doi.org/10.5194/egusphere-2023-1960
26 Sep 2023
 | 26 Sep 2023

Reconstruction of warm season temperatures in central Europe during the past 60,000 years from lacustrine GDGTs

Paul D. Zander, Daniel Böhl, Frank Sirocko, Alexandra Auderset, Gerald Haug, and Alfredo Martínez-García

Abstract. Millennial-scale climate variations during the last glacial period, such as Dansgaard–Oeschger (D/O) cycles and Heinrich events, have been extensively studied using ice core and marine proxy records. However, there is a limited understanding of the magnitude of these temperature fluctuations in continental regions, and questions remain about the seasonal signal of these climate events. This study presents a 60,000-year long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from lake sediments from the Eifel volcanic field, Germany. brGDGTs are bacterial membrane lipids that are known to have strong relationship with temperature, making them suitable for temperature reconstructions. We test several temperature calibration models on modern samples taken from soils and multiple maar lakes. We find a bias associated with water depth and anoxic conditions that can be corrected for by accounting for a brGDGT isomer that is only produced in anoxic conditions. The corrected temperature reconstruction correlates with proxy and model temperature record spanning the same time period, validating the calibration model. However, millennial-scale variability is significantly dampened in the brGDGT record, and in contrast to other northern hemisphere climate records, during several Heinrich stadials, temperatures actually increase. We demonstrate that these apparent discrepancies can be explained by the unique seasonal response of the brGDGT paleothermometer to temperatures of months above freezing (TMAF). Our data support the view that warm season temperatures in Europe varied minimally during the last glacial period, and that abrupt millennial-scale events were defined by colder, longer winters. Our continuous high-resolution temperature reconstruction provides important information about the magnitude of seasonal climate variability during the last glacial period that can be used to test climate models and inform studies of paleoecological change.

Paul D. Zander et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2023-1960', Francien Peterse, 27 Sep 2023
  • RC1: 'Comment on egusphere-2023-1960', Maria Fernanda Sanchez Goñi, 13 Oct 2023
  • RC2: 'Comment on egusphere-2023-1960', Anonymous Referee #2, 24 Oct 2023
    • AC2: 'Response to review from Anonymous Reviewer 2', Paul Zander, 05 Nov 2023

Paul D. Zander et al.

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Short summary
Bacterial lipids (branched glycerol dialkyl glycerol tetraethers; brGDGTs) extracted from lake sediments were used to reconstruct warm-season temperatures in central Europe during the past 60 kyr. Modern samples were used to test and correct for bias related to varying sources of brGDGTs. The temperature reconstruction is significantly correlated with other temperature reconstructions but features less millennial-scale variability, which is attributed to the seasonal signal of the proxy.