The project's primary goals are to document abrupt climate variations both past and present as recorded in ice cores recovered from the Guliya ice cap to assess how climate in northwestern Tibet has changed over recent centuries and millennia, and to determine the atmospheric, climatological, and glaciological dynamics that allowed the Guliya ice cap to survive since well before the beginning of the Holocene while other glaciers to the east and south appear to date back only to the Early to Middle Holocene. The Tibetan Plateau (TP) covers ~5 million km², and has ~46,000 glaciers that collectively contain one of Earth's largest stores of fresh water that feeds Asia's largest rivers and helps sustain 1.5 billion people. The Guliya ice cap (35^o 17'N; 81^o 30' E, 6710 masl), part of a large ice sheet in the western Kunlun Mountains (Fig. 1), is among the highest and largest ice caps outside the polar regions. The Ohio State University's Byrd Polar and Climate Research Center's Ice Core Paleoclimatology Research Group (ICPRG) drilled the first cores to bedrock on Guliya in 1992, recovering a long core from the plateau that yielded a climate record extending back through the Last Glacial Cycle and possibly longer (Thompson et al., Science, 1997). In 2015, the ICPRG and The Institute for Tibetan Plateau Research, Chinese Academy of Sciences, returned to Guliya and recovered two ice cores from the Guliya Plateau (GP), one 309.7 m to bedrock, and three cores from the Guliya Summit (GS, 6710 m asl), all to bedrock (~51 m). These are the first cores drilled from the summit.

The core to bedrock on the GP and two of the GS cores have been analyzed continuously from top to bottom in high-resolution for stable water isotopes, glaciochemistry, and mineral dust. Selected section of these cores have been analyzed for trace elements, black carbon, δ¹⁸O of air, and microbes. ¹⁴C analyses of discrete organic fragments, δ¹⁸O of air trapped in bubbles, analyses of additional chemical species, and the capability to analyze smaller samples improved the temporal resolution of the record, allowing us to refine the timescale of the first (1992) Guliya core.

It is well established that climate on the TP has been influenced over millennia by interactions between westerly and monsoon air masses driven by glacial boundary conditions, summer monsoon migration, and solar forcing. These ice core-derived records reveal the complex history of interactions between the summer monsoon and westerly air masses and document the history of temperature and precipitation in this region. During the Late Pleistocene (11.7 to ~15 ky BP) the warm, wet climate in the northwestern TP resulted from high summer insolation and intensified westerly precipitation which was directed toward the region by the retreat of the large Northern Hemisphere ice sheets. As the ice sheets in the high latitudes continued to retreat during the Early Holocene, both the westerlies and the Southwest Asian Monsoon moved northward. Recycled continental moisture originating in the North Atlantic was replaced by recycled monsoon moisture, albeit in smaller amounts resulting in arid conditions compared with the Late Pleistocene. Although summer insolation reached a maximum at the beginning of the Holocene, climate in the western TP was cooler, possibly due to a delayed response to ice sheet retreat to the north. The colder climate may have been conducive to the advance of glaciers on the TP during the Early Holocene. Climate warmed as the northern ice sheets retreated to reach their minimum surface area ~7.5 ky BP, and westerly precipitation moved southward into the western TP as the monsoon retreated to the south. After ~4 ky BP precipitation nearly doubled relative to that in the Early/Middle Holocene, possibly driven by increased recycling of moisture from the Mediterranean Sea and other large water bodies in Central Asia.  

During this project, four post-doctoral scholars, three females (one Hispanic) and one male, were mentored and advanced their careers with publication of four first-authored, peer-reviewed papers based on data from the Guliya ice cores. A female scholar currently serves as the PI on a successful NSF award to identify source areas for the very fine dust preserved at the bottom of the Guliya summit cores and thereby explore temporal changes in the prevailing wind. To date, there are eleven peer-reviewed publications with two additional papers ready for submission. Additional publications are expected on topics ranging from ice core dating, abrupt climate change, and the continued documentation of microbes (bacteria and viruses) in this extremely remote environment. These ice core-derived records provide a long-term context for climatic, atmospheric, and environmental variability in one of the least studied places on Earth and demonstrate that the western TP is now experiencing its warmest climate in the last ~12,000 years.

Last Modified: 09/28/2021
Modified by: Ellen Mosley-Thompson