Investigation of paleoclimatic hydroclimatic variability with emphasis on the role of oceanic circulation

Shailendra Pratap

Doctoral thesis

Abstract:

The growing concern regarding global warming emphasizes the critical need for an in-depth understanding of its impact on the water cycle, both locally and globally, given its significant impact on society. A prevailing hypothesis suggests that global warming will intensify the water cycle. However, uncertainties persist as some studies project drier climatic conditions. Hence, accurately predicting regional-level changes in the water cycle remains a challenge, hindering precise anticipation of future alterations. To overcome these limitations and uncertainties and to capture long-term climate patterns, this study employs a multi proxy data approach to investigate hydroclimate changes within warm climates. Furthermore, the study explores the influence of oceanic circulation on hydroclimatic variability. By examining past hydroclimate data sourced from natural archives, this research aims to establish valuable reference points aimed at enhancing the accuracy of climate models. Our study suggests that the hypothesis that a warmer climate is a wetter climate could be an oversimplification. This is because the water cycle exhibits considerable variability across different temporal and geographical contexts. Our observations highlighted dry conditions primarily associated with climates that are warmer than their centennial average, whereas slightly warmer climates, which are closer to their centennial average, tend to be correlated to wetter conditions on continents. Our findings provide new insights into the complex relationship between ocean circulation and shifts in the hydroclimate patterns, particularly emphasizing the Atlantic Meridional Overturning Circulation (AMOC). Our investigation reveals that the AMOC plays a critical role in shaping both global and regional changes in the hydroclimate/water cycle. Its fluctuations are intricately linked to instabilities in the state of the North Atlantic Ocean. For instance, a weakened AMOC may induce low sea surface temperatures and a southward shift in the Intertropical Convergence Zone. These changes limit the dispersion of atmospheric heat and moisture, thereby exerting a significant impact on the global hydroclimate. Furthermore, our study indicates that long-term changes in oceanic circulation patterns over the North Atlantic influence latitudinal temperature distributions, consequently affecting shifts in the hydroclimate/water cycle patterns at various latitudes.

Keywords

Hydroclimate variability, Water cycle intensification, Oceanic circulation, Global warming, Atlantic Meridional Overturning Circulation, Sea surface temperature

Language used: English

Date on which the thesis was submitted / produced: 1. 3. 2024

Thesis defence

• Supervisor: doc. Mgr. Ing. Ioannis Markonis, Ph.D.
• Reader: Roman Juras, Ph.D., Ing., Adam Vizina, externi, Nikolaos Mamassis, externi

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Doctoral programme / field:
Landscape Engineering / Environmental Modelling