This project will investigate past climates in the circum-Pacific region. Specifically, the project will evaluate hypothesized linkages between Southern Hemisphere and Northern Hemisphere climatic processes during the last glaciation, 100,000 to 10,000 years ago. Scientists have long recognized that Northern Hemisphere cooling and warming influence Southern Hemisphere climate, particularly in determining the broad patterns of glacial-interglacial cycles. Conversely, Southern Hemisphere climatic processes have only rarely been invoked as influences on Northern Hemisphere climate. Initial evidence shows apparent correlations in the timing of mountain glacier fluctuations in New Zealand, southern South America, the northwestern United States, and possibly other regions of the circum-Pacific. Those fluctuations occur during minima in Southern Hemisphere solar energy cycles, suggesting that Southern Hemisphere cooling is transmitted through both hemispheres in the Pacific region. This project will investigate glacial sediments and fossil insects in New Zealand and the northwestern US to test that hypothesis. The processes of mountain glaciation in both areas will be determined through detailed evaluation of glacial sediment sequences. The timing of the glacier fluctuations will be determined through optically-stimulated luminescence(OSL) dating of sand grains in the sediments, as well as crystal damage from ambient geological radiation, and on radiocarbon dating of organic sediments. Because glaciers fluctuate in response to both temperature and precipitation changes, the project will utilize fossil chironomids (non-biting midges)preserved in adjacent lake and pond sediments to determine water and air temperatures at specific times during the last glaciation.
A thorough evaluation of the timing of climatic changes around the Pacific Ocean margin will provide important insight into how the Earth's climate system functions. Climatic linkages are important to the modern climatic system,as shown by the global influence of El Nino and related processes. This project will therefore also help improve knowledge of how modern climate fluctuates. The project will enhance professional development of students and early career scientists, foster international collaboration, and strengthen educational offerings at three institutions. The project will provide ample opportunities for student research at both undergraduate and graduate levels.
