Browsing by Author "Thirumalai, Kaustubh"
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- Lessons from a high-CO2 world: an ocean view from ~ 3 million years agoPublication . McClymont, Erin L.; Ford, Heather L.; Ho, Sze Ling; Tindall, Julia C.; Haywood, Alan M.; Alonso-Garcia, Montserrat; Bailey, Ian; Berke, Melissa A.; Littler, Kate; Patterson, Molly O.; Petrick, Benjamin; Peterse, Francien; Ravelo, A. Christina; Risebrobakken, Bjørg; De Schepper, Stijn; Swann, George E. A.; Thirumalai, Kaustubh; Tierney, Jessica E.; van der Weijst, Carolien; White, Sarah; Abe-Ouchi, Ayako; Baatsen, Michiel L. J.; Brady, Esther C.; Chan, Wing-Le; Chandan, Deepak; Feng, Ran; Guo, Chuncheng; von der Heydt, Anna S.; Hunter, Stephen; Li, Xiangyi; Lohmann, Gerrit; Nisancioglu, Kerim H.; Otto-Bliesner, Bette L.; Peltier, W. Richard; Stepanek, Christian; Zhang, ZhongshiA range of future climate scenarios are projected for high atmospheric CO2 concentrations, given uncertainties over future human actions as well as potential environmental and climatic feedbacks. The geological record offers an opportunity to understand climate system response to a range of forcings and feedbacks which operate over multiple temporal and spatial scales. Here, we examine a single interglacial during the late Pliocene (KM5c, ca. 3:205 0:01 Ma) when atmospheric CO2 exceeded pre-industrial concentrations, but were similar to today and to the lowest emission scenarios for this century. As orbital forcing and continental configurations were almost identical to today, we are able to focus on equilibrium climate system response to modern and near-future CO2. Using proxy data from 32 sites, we demonstrate that global mean sea-surface temperatures were warmer than pre-industrial values, by 2:3 C for the combined proxy data (foraminifera Mg=Ca and alkenones), or by 3:2–3.4 C (alkenones only). Compared to the preindustrial period, reduced meridional gradients and enhanced warming in the North Atlantic are consistently reconstructed. There is broad agreement between data and models at the global scale, with regional differences reflecting ocean circulation and/or proxy signals. An uneven distribution of proxy data in time and space does, however, add uncertainty to our anomaly calculations. The reconstructed global mean seasurface temperature anomaly for KM5c is warmer than all but three of the PlioMIP2 model outputs, and the reconstructed North Atlantic data tend to align with the warmest KM5c model values. Our results demonstrate that even under low-CO2 emission scenarios, surface ocean warming may be expected to exceed model projections and will be accentuated in the higher latitudes.
- When eastern India oscillated between desert versus savannah‐dominated vegetationPublication . Zorzi, Coralie; Desprat, Stéphanie; Clément, Charlotte; Thirumalai, Kaustubh; Oliveira, Dulce; Anupama, Krishnamurthy; Prasad, Srinivasan; Martinez, PhilippeDuring the last glacial period, the tropical hydrological cycle exhibited large variability across orbital and millennial timescales. However, the response of the Indian summer monsoon (ISM), its related impact on terrestrial ecosystems, and associated forcing mechanisms remain controversial. Here we present a marine record of pollen-inferred vegetation changes suggesting that eastern India shifted from woody-savanna mosaics during Marine Isotopic Stage 3 to grasslands during the Last Glacial Maximum resulting from large-scale drying. Our data shows that ISM maximum is in phase with obliquity and precession maxima suggesting a dominant role of the Indian Ocean interhemispheric temperature gradient on glacial ISM variability. Persistent and abrupt dryland expansions of varying magnitude suggest rapid-scale onset of aridity during Heinrich Stadial events and during the Toba eruption. We propose that the amplitude of ISM drought events are initiated by high latitude and volcanic forcings, although modulated by precession.