Address the impacts of changing ocean circulation on US hydroclimate
PI: Laifang Li (Meteorology and Atmospheric Science)
The PI and Co-PI will aim to recruit a post-comp graduate student (no tuition charge), or a postdoc research for whom the remainder of the salary will be covered by a recent grant for postdoc from the EMS dean’s office.
Co-PI: Xichao Chen (Department of Meteorology and Atmospheric Science, and ADAPT)
Project Description
The Atlantic Meridional Overturning Circulation (AMOC), also known as the ocean’s great conveyor belt, is the most e ective poleward energy transport mechanism in the Earth’s climate system (Buckley and Marshall 2016). The AMOC is driven by the formation of dense deep water in the subpolar North Atlantic, which is very sensitive to global climate change. Since the 1970s, the AMOC has slowed down by 10% and will continue to be weakened by the end of the 21st Century. The consequence of the AMOC slowdown, however, is regime dependent. The ongoing research from the PI’s group showed that when AMOC slows down to 50% of its current strength, the ocean heat balance mechanisms in the subpolar North Atlantic will be substantially changed: i.e., the ocean will no longer actively uptake heat but rather acts as a passive response to the overlying atmosphere (Fan et al. 2025). This 50% slowdown or more is projected to take place around 2070s, if we take our current socioeconomic pathway (Boer 2022). However, how the climate system will adjust to this new AMOC regime, especially how the hydroclimate in the conterminous US will response, remains an open question.
This project aims to answer this open question by synergistically using global climate model out from the North Atlantic Hosing Model Intercomparison Project (NAHosMIP; Jackson et al. 2023) and the numerical downscaling with regional climate models. Firstly, the simulations from the NAHosMIP will be analyzed. The NAHosMIP aims to address the degree of AMOC slowdown given di erent dosage of freshwater flux in the subpolar North Atlantic. Based on our current study, only the simulations that generate more than 50% slowdown in AMOC will be selected. We will then compare the large-scale atmospheric circulation and US precipitation changes after the 50% slowdown of the AMOC. The analysis of US precipitation change from the global climate models only provides a basin-line estimation of AMOC’s impacts on US hydroclimate. More local and small-scale processes essential for precipitation needs higher-resolution and regional specific models. As a next step, the model simulated large-scale parameters will be downscaled using a regional climate model, the Weather Research and Forecast (WRF) model. The WRF model simulation will cover the entire US, and the simulation will be performed at a horizontal resolution of 3 km. Two sets of experiments will be performed, with the first set being control run and the second set being the AMOC slowdown simulation. In the control simulation, the boundary and initial condition will be prescribed by the atmospheric reanalysis; whereas in the AMOC slowdown simulation, the changes in the boundary condition as derived from the NAHosMIP will be super-imposed into the reanalysis. From the WRF simulations, we will quantify precipitation changes (mean, variance, and spatiotemporal variability) due to AMOC slowdown. In addition, the precipitation generation processes will be diagnosed to explore the mechanisms involved.
Specific Areas of Computational and/or Data Science Expertise the current team is particularly interested in recruiting are: 1) parallel programming; 2) familiarity with data from the model intercomparison projects; 3) experience with WRF modelling; 4) ability to compute climate variables in various coordinate systems (e.g., density coordinate for ocean circulation and pressure coordinate for atmospheric humidity).
Requirements and Expectations: The project looks for a highly motivated junior researcher with background in atmosphere, ocean, and climate dynamics. The researcher is expected to work in a collaborative environment, bridging the existing expertise between the PI and Co-PI research groups. Research progress should be reported to the PIs in a timely and regular manner through written report or oral presentation during weekly group meetings.
Specific Objectives: The project outcome will be utilized as preliminary data for applications of external grant (e.g., NSF CLD, NOAA CPO, and NASA GEWEX). With the PI and Co-PI’s unique expertise in our field of expertise, we expect at least two peer-reviewed journal articles from the project.
Medium to Long-Term Goals: 1) obtain external grant on research for ocean’s climatic impacts on land territory; 2) use the regional climate downscaling to inform future climate change in the US; 3) expand the WRF simulations to study climate in the past, which in combination with land-based proxy records, will be applied to infer AMOC variability in the geological past.
Connection to ICDS’s mission: The project will support the interdisciplinary collaboration between two junior faculty members. The results from high-resolution numerical modeling advance our knowledge and mechanistic understanding of Earth system changes due to human activities.
Recent and planned engagement with ICDS: The PI is an ICDS co-hire and the Co-PI is assistant director of the ADAPT. They have participated in multiple ICDS sponsored activities. For example, the PI have judged the poster presentations for the past ICDS symposium since 2021. Her students present their research at the past symposiums as well. Through this ICDS support, the PI, Co-PI and the selected junior researcher will plan to: 1) present the research f indings at the upcoming ICDS symposium; 2) publish papers acknowledging ICDS as a iliation and funding source (if funded); and 3) plan workshops on US climate and/or ocean dynamics through the co-host by the Department of Meteorology and ICDS.