Periodic Reporting for period 1 - ICECAP (Investigation of Climatic Events - Cooling and Ash in the Palaeogene)
Periodo di rendicontazione: 2021-10-18 al 2023-10-17
ICECAP set out to improve understanding of regional to global climate feedback mechanisms during periods of rapidly evolving CO2 levels, through the study of a period analogous to the near-future Earth, namely, the Paleogene. ICECAP also aimed to solve the question of glendonite significance in the geological record (from Phanerozoic to Recent). This project has implications for both future climate forecasting under predicted CO2 levels, and for palaeoclimatic reconstructions on regional and global scales throughout geological time. To these aims, ICECAP had the following specific objectives: (1) To develop a high-resolution climatic reconstruction for the Palaeogene successions of Denmark and Northeast Atlantic Margin, identifying the magnitude and duration of these cooling events within the longer-term trends and to examine their extent by comparison between the two cores and with published global records from this time. (2) To obtain multi-proxy, quantitative temperature reconstructions for glendonites and glendonite-bearing sedimentary horizons from other Palaeogene successions around the globe in order to understand the climatic significance of glendonites in the geological record. (3) To generate a database of organic and inorganic chemical data for glendonites from Palaeogene successions around the globe, that will be used to understand the (bio)geochemical requirements for glendonite formation, with implications for the significance of glendonites in the geological record as palaeo-environmental indicators. (4) To use the climatic and geochemical data to develop a model for the mechanism for transient cooling events and glendonite formation in the Danish early Palaeogene succession, and so solve how regionalised cooling can occur in a greenhouse world. ICECAP met these objectives through publication of the planned deliverables laid out in the project proposal.
The samples for objective 1 were collected during the Exp. 396 sampling party to Bremen and during fieldwork in Svalbard August 2023. The data for this objective were collected during the secondment visits to University of Utrecht and by sending off samples prepared at the University of Oslo for stable isotope analysis. Some of the findings were presented at EGU 2023 (Vickers et al., 2023, EGU23-5465). The publications arising are in prep. The data for Objective 2 were collected during the secondment trips to both University of Utrecht and ETH Zürich. The data and initial interpretations were presented at EGU 2022. One paper dealing with clumped isotope methodology has been published in GCA (Looser et al., 2022) and the main paper arising from this work is in prep. The scope of objective 3 was expanded to cover glendonites from all geological time. The database has been made yet remains to be entirely published (2 arising publications still in review or in prep.), but parts of the database have been published in Counts et al. (accepted, JSR); Vickers et al., (2024, CoP); Schultz et al. (2023, NJG), and Vickers et al. (2022, GCA). A further two papers are in review (Jelby et al. (GSL Spec. Pub.) or in prep (Vickers et al., Cret. Res.). Further data was presented at several international conferences, including Goldschmidt 2023 and CBEP 2022.
Objective 4 set out to develop a model to explain the evidence for cooling during the early Paleogene prevailing greenhouse – hothouse climate, building on the findings from the pervious objectives. Various potential hypotheses to explain the evidence for cooling are presented in Vickers et al. (2024 CoP), and a paper presenting evidence to support one particular hypothesis is in prep.
Objective 4 set out to develop a model to explain the evidence for cooling during the early Paleogene prevailing greenhouse – hothouse climate, building on the findings from the pervious objectives. Various potential hypotheses to explain the evidence for cooling are presented in Vickers et al. (2024 CoP), and a paper presenting evidence to support one particular hypothesis is in prep.
The most significant finding of the project ICECAP is that short-duration volcanically-driven cooling down to near-freezing temperatures appear to punctuated the extreme warmth of the Paleocene-Eocene Thermal Maximum (PETM) hyperthermal, a period of rapidly evolving atmospheric CO2 analogous to modern anthropogenically-driven CO2 changes. ICECAP results suggest that the PETM event may have been more different from modern climate than previously thought, as the massive global-scale volcanism that was occurring synchronously with this climate-change event had more effect, and more varied effect, on regional- to global climate than previously thought. This volcanism may have induced short-duration cooling, and given the unique paleogeography of the Nordic Seas region, this meant that near-freezing temperatures persisted at the bottom of the ocean in this area for potentially decadal to perhaps century timescales, during an otherwise globally hothouse period. This underlines the need to understand both regional- and sub-geological time- scale details of Earth climate feedbacks, if we are to accurately use climate models to forecast the long-term effects of current atmospheric CO2 increase.