"Climate tipping cascade": The Amazon Rainforest and the West Antarctic Ice Sheet behavior under sustained global warming

• Grant number: 24/04935-9
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: September 01, 2024
• End date: August 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Paulo Eduardo de Oliveira
• Grantee: Marcelo Augusto de Lira Mota
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 18/23899-2 - Trans-Amazon Drilling Project: origin and evolution of the forests, climate, and hydrology of the South American tropics, AP.PFPMCG.TEM

Abstract

Modeled simulations suggest that, under current carbon dioxide (CO2) emissions, global warming will exceed 1.5°C within this century. Consequences include the triggering of unavoidable and/or irreversible climate tipping points (CTPs). These are critical thresholds that may lead to, for instance, substantial sea-level rise from collapsing ice sheets such as the West Antarctic Ice Sheet (WAIS), and the dieback of biodiverse biomes such as the Amazon Rainforest (AMAZ). The WAIS is mostly marine-based and hence very sensitive to a changing climate. It is hypothesized that previous warmer intervals have led to past collapses of the WAIS. The AMAZ is an important carbon sink. However, its capacity has declined, mostly due to a drying trend which tend to be worsened by further warming. CTPs are not isolated components, as they interact on a global scale. Overall tipping of one element increases the likelihood of tipping others, possibly risking a "tipping cascade" of impacts that may further amplify global warming. However, it remains unclear whether a tipped WAIS would have influence on the climate in the AMAZ. Direct evidence for such scenario comes from Pliocene and Pleistocene records recovered on a highly dynamic polar ice sheet (i.e. the WAIS) and coastal settings in the AMAZ. Here I will investigate the impacts of sustained global warming and major ice-sheet collapse in the Amazon Rainforest through palynological records based on marine/terrestrial palynomorphs and palynofacies from offshore Amundsen Sea Embayment (WAIS) and coastal AMAZ. Overall, ~300 samples are expected to be processed for palynology: ~200 samples from sites U1532 and U1533, WAIS, recovered by the International Ocean Discovery Program (IODP) Expedition 379 to the Amundsen Sea; and ~100 samples from site TADP-MA1, Marajó Basin, AMAZ, to be retrieved by the Trans-Amazonian Drilling Project (TADP). By applying statistical analyses to palynomorph/palynofacies counts, I will provide palynomorph/palynofacies-based proxies. Along with independently generated post-cruise/-drilling proxies, these data will yield new Pliocene-Pleistocene, high-resolution temporal records. Multi-proxy analysis will allow to accurately detecting which variations in phytoclasts, palynomorphs and/or dinocyst assemblages are due to a particular paleoenviromental control. Coeval WAIS and AMAZ records will enable correlations between past collapses of the WAIS and precipitation/sea-level changes in the AMAZ, as well as the test of the main hypotheses raised by this Project. This Project is feasible within a 24-month term due to: readily available samples, suitable infrastructure, and potential for external collaborations. After the publication of the Project results in peer-reviewed scientific journals, new data will be released to the scientific community through specialized open access repositories or as supplementary material to the paper itself. Physical samples/slides will be donated to the scientific collection of the Host Institution. By the end of this Project, I intend to have provided: [1] an unprecedented, high-resolution palynological record of the Pliocene-Pleistocene of the Amundsen Sea and the Marajó Basin, including taxonomic description at species level for dinocysts; [2] the identification of paleoecological (salinity, productivity, sea-surface temperature) changes of dinocysts assemblages in both study areas; [3] the evaluation of the response of high-latitude dinocyst assemblages to the warming/cooling of the sea surface produced during advance and retreat events of the WAIS; and [4] a correlation of episodes of sustained warming, WAIS collapse, and changing climate and sea level in the AMAZ.