Periodic Reporting for period 4 - SPANC (Evolution and Variability of Climate Sensitivity and Polar Amplification during CeNozoic Warm Climates SPANC)
Berichtszeitraum: 2023-03-01 bis 2024-02-29
Forecasting the magnitude of future global warming is among the grand scientific challenges. Model estimates of long-term warming resulting from a doubling of the CO2 concentration relative to the pre-industrial era (termed Equilibrium Climate Sensitivity, ECS) range between 1.5 and 4.5 °C. Moreover, polar regions warm more than low latitude regions, termed polar amplification (PA), but the magnitude of PA is difficult to quantify because it is caused by several factors, the effect of which cannot be separated with observations. These large uncertainties may represent the difference between the melting or conservation of large continental ice sheets, and between habitable and inhabitable regions. SPANC set out to quantify ECS and PA through accurate reconstructions of past climate change using sediments accumulated on ocean floors, thereby particularly focusing on estimates of past warm climates that can serve as analogs for the future.
We generated unprecedented-resolution climate reconstructions for, respectively, the Eocene and Miocene. Based on stratigraphic ground-work, this was fully established for the Miocene and Eocene. These records are subsequently used to quantify polar amplification of orbital-scale global temperature variability. The target of climate sensitivity was certainly assessed but we were not able to provide more accurate numbers than those available due to Covid19-related delays in the development of a new method to reconstruct atmospheric CO2 concentrations. However, instead, we have now far better-than-anticipated control on the evolution and orbital-scale variability of (tropical) paleotemperature for both the Miocene and Eocene and associated (sub)tropical monsoon dynamics under warm climate regimes (see above-cited papers).
We generated unprecedented-resolution climate reconstructions for, respectively, the Eocene and Miocene. Based on stratigraphic ground-work, this was fully established for the Miocene and Eocene. These records are subsequently used to quantify polar amplification of orbital-scale global temperature variability. The target of climate sensitivity was certainly assessed but we were not able to provide more accurate numbers than those available due to Covid19-related delays in the development of a new method to reconstruct atmospheric CO2 concentrations. However, instead, we have now far better-than-anticipated control on the evolution and orbital-scale variability of (tropical) paleotemperature for both the Miocene and Eocene and associated (sub)tropical monsoon dynamics under warm climate regimes (see above-cited papers).
The hiring of the personnel and acquisition of the UHPLCMS system went as desired, though with some delay. Contrary to expectations, the IRMS system has been still running fine. The surplus has been used to compensate the PhD students for significant time loss during the Covid-crisis.
Scientifically, the project started out reasonably well. Work Package 1 was delayed immediately and was hampered significantly due to the Covid Crisis. Despite, We published one manuscript related to dinoflagellate toxicity and CO2 availability as well as a literature review on experimental studies reporting algal 13C-fractionation and discovered that experimental setup is a major factor in determining algal 13C-fractionation in cultures. This was long suspected by a part of the community but discarded by another part. One paper regarding the temperature-dependence of 13C-fractionation is still in preparation.
The projects in WP 2 and 3 started up as desired with the generation of a large amounts of temperature reconstructions for the Miocene and Eocene starting early 2019, essentially as anticipated following the start of PhD students Chris Fokkema (June 2019) and Evi Wubben (September 2019). Also this fell apart in March 2020 due to Covid-19-related lockdown and lab closure. Laboratory closures and restricted lab working has been a huge brake on SPANC, as this is a particularly data-intensive project. We have been able to work efficiently and despite the capacity limit. Because of reallocations of budgets, I have been able to generate a large part of the originally scheduled data, through additional analysts and contract extensions of the PhD students.
Despite these setbacks, both PhD students have accomplished milestones.
Collectively, we have calibrated our new CO2 proxy, which is based on the CO2-dependent chemical composition of fossil algae, so that it can be used for coupled CO2 and temperature reconstructions on the same sediment samples. Moreover, we have generated high-quality coupled CO2 and temperature reconstructions for the ice-free early Eocene and the warm but glaciated middle Miocene at unprecedented resolution. This has allowed for refined estimates of ECS but particularly, we have now unprecedented controle on the amplification of temperature changes towards polar regions, crucial for ice sheet extent and volume and hence global sea levels. Collectively, this work has led to the first-ever quantification of orbital scale global temperature variability for the Eocene and its polar amplification; reproduced at two sites. Moreover, the analyses have resulted in the first-ever orbital-scale temperature record for the early-middle Miocene, revealing paleo-monsoon dynamics and its dependency of global warming.In addition, we have delivered the first global assessment of climate change across the early-middle Miocene and its polar amplification. Furthermore, the work has led to the first-ever quantification of orbital scale Eocene hydrological variability in an arid zone. Finally, we obtained evidence to support the conclusion that tropical early Eocene phytoplankton communities were resilient to multi-millennial-scale warming of up to approximately ~1.5 ºC. All of these achievements, and more, are breakthroughs and have brought the field significantly beyond the state of the art. Many results were however in the range of expected values. However, we did not expect the warming from the early-middle Miocene to be so little. Unexpected were the fact that carbon cycle feedbacks to orbital cyclicity in the Eocene were very strong, causing large atmospheric pCO2 variations and global temperature variations. Also unexpected was the resilience in tropical ecosystems to transient temperature changes of up to 1.5 °C, which may provide some hope for the impact of current warming.
Scientifically, the project started out reasonably well. Work Package 1 was delayed immediately and was hampered significantly due to the Covid Crisis. Despite, We published one manuscript related to dinoflagellate toxicity and CO2 availability as well as a literature review on experimental studies reporting algal 13C-fractionation and discovered that experimental setup is a major factor in determining algal 13C-fractionation in cultures. This was long suspected by a part of the community but discarded by another part. One paper regarding the temperature-dependence of 13C-fractionation is still in preparation.
The projects in WP 2 and 3 started up as desired with the generation of a large amounts of temperature reconstructions for the Miocene and Eocene starting early 2019, essentially as anticipated following the start of PhD students Chris Fokkema (June 2019) and Evi Wubben (September 2019). Also this fell apart in March 2020 due to Covid-19-related lockdown and lab closure. Laboratory closures and restricted lab working has been a huge brake on SPANC, as this is a particularly data-intensive project. We have been able to work efficiently and despite the capacity limit. Because of reallocations of budgets, I have been able to generate a large part of the originally scheduled data, through additional analysts and contract extensions of the PhD students.
Despite these setbacks, both PhD students have accomplished milestones.
Collectively, we have calibrated our new CO2 proxy, which is based on the CO2-dependent chemical composition of fossil algae, so that it can be used for coupled CO2 and temperature reconstructions on the same sediment samples. Moreover, we have generated high-quality coupled CO2 and temperature reconstructions for the ice-free early Eocene and the warm but glaciated middle Miocene at unprecedented resolution. This has allowed for refined estimates of ECS but particularly, we have now unprecedented controle on the amplification of temperature changes towards polar regions, crucial for ice sheet extent and volume and hence global sea levels. Collectively, this work has led to the first-ever quantification of orbital scale global temperature variability for the Eocene and its polar amplification; reproduced at two sites. Moreover, the analyses have resulted in the first-ever orbital-scale temperature record for the early-middle Miocene, revealing paleo-monsoon dynamics and its dependency of global warming.In addition, we have delivered the first global assessment of climate change across the early-middle Miocene and its polar amplification. Furthermore, the work has led to the first-ever quantification of orbital scale Eocene hydrological variability in an arid zone. Finally, we obtained evidence to support the conclusion that tropical early Eocene phytoplankton communities were resilient to multi-millennial-scale warming of up to approximately ~1.5 ºC. All of these achievements, and more, are breakthroughs and have brought the field significantly beyond the state of the art. Many results were however in the range of expected values. However, we did not expect the warming from the early-middle Miocene to be so little. Unexpected were the fact that carbon cycle feedbacks to orbital cyclicity in the Eocene were very strong, causing large atmospheric pCO2 variations and global temperature variations. Also unexpected was the resilience in tropical ecosystems to transient temperature changes of up to 1.5 °C, which may provide some hope for the impact of current warming.
We will provide a novel, calibrated proxy for paleo-pCO2 based on dinoflagellate cyst 13C-fractionation
We will provide accurate reconstructions of paleo-CO2 concentrations
We will provide accurate reconstructions of Miocene and Eocene Polar amplification
We will provide novel insights into paleoclimate sensitivity to CO2 forcing
We will provide accurate reconstructions of paleo-CO2 concentrations
We will provide accurate reconstructions of Miocene and Eocene Polar amplification
We will provide novel insights into paleoclimate sensitivity to CO2 forcing