580 California St., Suite 400
San Francisco, CA, 94104
Key research themes
1. How did the onset and intensification of Northern Hemisphere glaciation (NHG) unfold regionally during the late Pliocene to early Quaternary, and what were the main drivers?
This theme investigates the timing, sequence, and mechanisms behind the transition from a warm Pliocene climate to intensified glaciations in the Northern Hemisphere starting ∼3 to 2.6 million years ago. The research focuses on the spatiotemporal heterogeneity of cooling and glaciation signals across different latitudes, the influences of CO2 concentration thresholds, tectonic changes, and shifting oceanic and atmospheric circulations. Understanding this transition is critical for elucidating feedbacks within the Earth climate system and paleoclimate forcings that shaped the modern icehouse world.
Key finding: This study provides evidence that global cooling from the warm Pliocene to modern conditions was a gradual process occurring regionally at different times rather than a synchronous threshold event. It demonstrates that... Read more
Key finding: This paper disentangles the onset (~3 Ma) and intensification (~2.7 Ma) of NHG, revealing distinct regional climate and ocean circulation responses over this interval. It establishes that the gradual transition to bipolar... Read more
Key finding: This work enhances the chronologic framework for deglaciation after the Last Glacial Maximum in North America, providing a refined sequence of retreat for major ice sheets from 18 ka to 1 ka. By compiling over 5,000... Read more
Key finding: This synthesis integrates surface exposure ages and hydrological data to outline a model where glacial maxima in the Central Andes exhibit latitudinally variable timing, with tropical glaciers responding primarily to... Read more
2. What are the spatial and temporal patterns of climate variability during the Late Glacial and Holocene in the Northern Hemisphere mid- to high-latitudes?
This research area synthesizes proxy records to reconstruct precipitation isotopic compositions, temperature changes, and glacier dynamics through the transition from the Last Glacial Maximum (LGM) into the Holocene. It explores how regional climatic changes such as glacial advances and retreats, isotopic precipitation shifts, and atmospheric circulation variability developed, their spatial heterogeneity, and implications for understanding mechanisms driving abrupt and gradual climate changes during this interval.
Key finding: By compiling 86 globally distributed groundwater, speleothem, and ice core isotope records, this study identifies broad spatial patterns where high latitude and continental interiors had strong negative precipitation δ18O... Read more
Key finding: Through glacial snow mass balance modeling and review of paleoenvironmental data, this study shows that moderate cooling (1-4°C) coupled with shifts in synoptic climatology and enhanced westerly moist airflow can produce... Read more
Key finding: This review critically evaluates chronological methods for Last Interglacial (∼140–105 ka) climate records from diverse proxies and archives, emphasizing substantial absolute and relative age uncertainties. It shows that... Read more
Key finding: By reconstructing winter-spring temperatures from lake sediment alkenone biomarkers and modeling lake ice thermodynamics in Arctic Alaska, this study demonstrates continuous winter-spring warming through the Holocene... Read more
3. How did terrestrial ecosystems, soil weathering, and chemical weathering proxies respond to late Quaternary climate variations, especially during glacial-interglacial transitions?
Research under this theme focuses on paleoecological and geochemical proxies to reconstruct vegetation dynamics, soil weathering intensity, and landscape responses to climate changes over the last glacial cycle and Holocene. It examines relationships between temperature, precipitation, atmospheric CO2, and biological activity to interpret chemical index of alteration (CIA) values and biotic community shifts as indicators of past climate variability, highlighting regional ecosystem sensitivity and feedbacks within the Earth system.
Key finding: This study illustrates that late Quaternary climate changes in southern Africa primarily affected community dynamics within existing biomes rather than wholesale biome migrations. It demonstrates that species-level responses... Read more
Key finding: This review consolidates evidence that variations in CIA values in soils and sediments effectively reflect climate-driven changes in chemical weathering intensity linked to temperature and precipitation variations during... Read more
Key finding: By comparing greenhouse gas trends and temperature proxies from the late Holocene to earlier interglacials, this paper shows anomalous increases in CO2 and CH4 during the last 7,000 years inconsistent with natural orbital... Read more