Collaborative Research: NSFGEO-NERC: P2C2--Understanding Trans-Hemispheric Modes of Climate Variability: A Novel Tree-Ring Data Transect spanning the Himalaya to the Southern Ocean

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The mechanisms that govern trans-hemispheric climate linkages and those between the tropics and higher latitudes are not well understood. This gap in knowledge is caused by a lack of high resolution and well dates records of past climate variability. The sparsity of the data coverage as well as the lack of common climate oscillatory modes in the western Pacific region limits the understanding of broader-scale climate teleconnections on interannual to decadal time scales. This project aims to develop a new data network of temperature and hydroclimate variability across a transect spanning from the Himalaya to the Southern Ocean and extending back to 500-1000 years. This is a project that is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.The researchers will repurpose existing tree ring samples collected from the broader monsoon Asia down to the southern middle latitudes and use a new tracer (proxy), blue light intensity, as an indicator of temperature and hydroclimate. This new proxy will enhance prior climate analyses based almost entirely on the single total ring-width parameter and will be used to model and reconstruct key modes of atmosphere-ocean variability between the northern and southern hemispheres. Specifically, the researchers will use these data to address the following questions: (1) What are the climatic impacts of past volcanic events in the tropics and Southern Hemisphere? (2) How have the Intertropical Convergence Zone and El nino Southern Oscillation varied and interacted over the past 500-1000 years as expressed across the tropical Indo-Pacific region? and (3) How has the Southern Annular Mode varied over the past millennium, and how is it driven by tropical and other forcing?The potential broader impacts include an improved understanding of past variability in the climate-sensitive yet data-sparse Eastern Hemisphere which includes some of the most climatically vulnerable regions of the globe. These data will be disseminated to the broader scientific community via public repositories and at scientific conferences; and will be included in a future iteration of the Monsoon Asia Drought Atlas. The project will support the training of three undergraduate students at Rider university and foster national collaborations between Columbia University and Ryder University and international collaborations with universities in the UK, Czech republic, Australia and New Zealand.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.