fnctId=thesis,fnctNo=367
Mechanisms Driving Changes in Sea Surface Temperature Seasonal Cycle in a Warmer World
- 작성자
- 기후시스템전공
- 저자
- Anila Rani Jo
- 발행사항
- 발행일
- 2024-08
- 저널명
- 국문초록
- 영문초록
- Amplification of sea surface temperature (SST) seasonality in response to global warming is a robust feature in future climate. Season-dependent regional disparities in the SST seasonal cycle amplification and the associated mechanisms need to be better addressed. This thesis explores the evolving landscape of SST in response to climate change, focusing on understanding the intensification of the SST seasonal cycle. Recent observations highlight a notable rise in global SST, prompting concerns about its profound implications for Earth's climate system. The thesis examines (1) assess the robustness of SST seasonality intensification, (2) examine the role of enhanced stratification in driving the SST seasonal cycle amplification, and (3) identify the physical mechanisms responsible for spatiotemporal variations in SST seasonality in response to future warming. The study employs a comprehensive approach, integrating data from Coupled Model Intercomparison Project Phase (CMIP) 5 and 6 and large ensemble simulations using Community Earth System Model version 2 (CESM2LE) models. The first part investigates the global amplification of the SST seasonal cycle, attributing the phenomenon to enhanced stratification. By the end of the 21st century, in the RCP 8.5 scenario, the amplitude of the SST seasonal cycle increases by 30 % on average, where the SST seasonal cycle is defined as the difference between climatological maximum and minimum temperature. Findings reveal a consistent amplification, particularly in mid- and high-latitude regions of the Northern Hemisphere. Analyzing a simplified mixed layer heat budget shows that the amplification can be attributed to the upper ocean's increasing stratification and, consequently, the shoaling of the annual mean mixed layer. The North Atlantic, North Pacific, and South Indian Oceans emerge as focal points for understanding the robustness of SST seasonality amplification.In the second part, the research delves deeper into season-dependent regional disparities in this amplification and the associated mechanisms. Here, the study investigates detailed spatiotemporal characteristics of the amplification, focusing on the North Pacific and North Atlantic, where robust changes are projected to emerge around 2050 by employing CESM2-LENS simulations under the SSP3-7.0 scenario. The study unravels complex interplays of atmospheric and oceanic processes driving SST seasonality changes. The results indicate that atmosphere-ocean coupled processes shape regional changes in SST seasonality differently between warm (MAMJJAS) and cold seasons (ONDJF). The projected warming tendency during warm season is mainly due to increased net surface heat flux and weakening of vertical mixing. On the other hand, during the cold season, the projected cooling tendency is driven by strengthened vertical mixing over the North Pacific associated with the weakening of wind but, over the North Atlantic, weakened horizontal advection and mixing due to changes in ocean currents.While providing crucial insights into the mechanisms behind SST seasonality changes, the study acknowledges limitations, including excluding polar regions in specific analyses and potential model dependencies. With implications for weather patterns, marine ecosystems, and climate resilience tactics, these findings enhance the understanding of how climate change affects SST dynamics. The study underscores the urgency of continued research to refine models, address uncertainties, and guide effective climate change mitigation and adaptation measures.
- 일반텍스트
- 첨부파일