A5041622885- Geology and Paleoclimatology Research
- Geological formations and processes
- Isotope Analysis in Ecology
- Geological Studies and Exploration
- Marine and environmental studies
- Hydrology and Sediment Transport Processes
- Pleistocene-Era Hominins and Archaeology
- Archaeology and ancient environmental studies
- Water Quality and Resources Studies
- Hydrocarbon exploration and reservoir analysis
- Cryospheric studies and observations
- Archaeology and Natural History
- Methane Hydrates and Related Phenomena
- Water Resources and Management
- Coastal wetland ecosystem dynamics
- Geomagnetism and Paleomagnetism Studies
- Geological and Geochemical Analysis
- Tree-ring climate responses
- Soil erosion and sediment transport
- earthquake and tectonic studies
- Geochemistry and Geologic Mapping
- Landslides and related hazards
- Coastal and Marine Dynamics
- Climate change and permafrost
- Geochemistry and Elemental Analysis
University of Minnesota, Duluth
2009-2022
Woods Hole Oceanographic Institution
1993-2020
United States Geological Survey
1997-2011
University of Minnesota
2007
Woodwell Climate Research Center
2000-2006
Pacific Island Ecosystems Research Center
2003-2006
University of Nebraska–Lincoln
2000
Geological Society of America
1998
NOAA Great Lakes Environmental Research Laboratory
1992
United States Department of the Interior
1980-1990
Two atmospheric circulation systems, the mid-latitude Westerlies and Asian summer monsoon (ASM), play key roles in northern-hemisphere climatic changes. However, variability of Asia their relationship to ASM remain unclear. Here, we present longest highest-resolution drill core from Lake Qinghai on northeastern Tibetan Plateau (TP), which uniquely records both since 32 ka, reflecting interplay these two systems. These document anti-phase for glacial-interglacial glacial millennial...
Deciphering the evolution of global climate from end Last Glacial Maximum approximately 19 ka to early Holocene 11 presents an outstanding opportunity for understanding transient response Earth's system external and internal forcings. During this interval warming, decay ice sheets caused mean sea level rise by 80 m; terrestrial marine ecosystems experienced large disturbances range shifts; perturbations carbon cycle resulted in a net release greenhouse gases CO(2) CH(4) atmosphere; changes...
Lake Superior summer (July–September) surface water temperatures have increased approximately 2.5°C over the interval 1979–2006, equivalent to a rate of (11 ± 6) × 10 −2 °C yr −1 , significantly in excess regional atmospheric warming. This discrepancy is caused by declining winter ice cover, which causing onset positively stratified season occur earlier at roughly half day per year. An start increases period lake warms during months, leading stronger trend mean than would be expected from...
Abstract Summer temperatures on the Tibetan Plateau (TP) significantly affect stability of glaciers that provide steady water resources to nearly half world population. However, lack reliable, long‐term proxy records greatly impedes understanding regional temperature sensitivity climate forcings. Here we present a 16 ka long, alkenone‐based summer record from Lake Qinghai, northeastern TP demonstrates major response changes in insolation and Atlantic Meridional Overturning Circulation during...
Abstract The scarcity of documented numerical relations between rock weathering and time has led to a common assumption that rates are linear. This been strengthened by studies have calculated long-term average rates. However, little theoretical or empirical evidence exists support linear for most chemical-weathering processes, with the exception congruent dissolution processes. few previous rock-weathering contain quantitative documentation relation chemical suggest processes decrease time....
A 100‐yr‐long time series of water temperature measured just downstream Lake Superior is used to produce proxy open‐lake temperature. This analysis suggests that open‐water summer temperatures have increased by roughly 3.5°C over the last century, most warming occurring in three decades. Correspondingly, length positively stratified season has from 145 d 170 d. The observed amount greater than change regional same period a factor two. discrepancy can be understood context reduced winter ice...
Previous work Acknowledgments General description of weathering rinds on andesitic and basaltic stones Factors affecting weathering-rind thickness Sampling design methods Structure the data Areas types deposits sampled Sample site selection collection Measurement procedures Environmental factors other than time Topographic position Parent material Vegetation Climate Summary The relation between development Weathering as an indicator relative age Page 1
Weathering rinds on basaltic and andesitic stones preserve the alteration products of these lithologies under conditions that preclude detrital contamination, physical removal, uncertainty original composition.The mineralogy chemistry samples weathering from several areas with temperate climates in Western United States were studied using a variety analytical methods, including thin-and polished sections, X-ray diffraction, differential thermal analysis, scanning electron microscopy, energy...
Research Article| July 01, 1986 Effect of height and orientation (microclimate) on geomorphic degradation rates processes, late-glacial terrace scarps in central Idaho KENNETH L. PIERCE; PIERCE 1U.S. Geological Survey, Box 25046, M.S. 913, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar STEVEN M. COLMAN 2U.S. Woods Hole, Massachusetts 02543 GSA Bulletin (1986) 97 (7): 869–885. https://doi.org/10.1130/0016-7606(1986)97<869:EOHAOM>2.0.CO;2...
Paleoclimate proxy records reveal a pervasive cooling event with Northern Hemispheric extent approximately 9300 years ago. Coeval changes in the oceanic circulation of North Atlantic imply freshwater forcing. However, source, magnitude, and routing meltwater have remained unknown. Located central America, Lake Superior is key site for regulating outflow glacial to oceans. Here, we show evidence an 45-meter rapid lake-level fall this basin, centered on calibrated before present, due failure...
Abstract Classification of Quaternary dating methods should be based on the level quantitative information and degree confidence contained in age estimates produced by methods. We recommend use terms numerical-age, calibrated-age, relative-age , correlated-age to describe these levels. also classify type into sideral, isotopic, radiogenic, chemical biological, geomorphic, correlation The “absolute” is inappropriate for most methods, replaced “numerical.” “date” minimized favor “age” or “age...
The diffusion equation derived from the continuity for hillslopes is applied to scarp erosion in unconsolidated materials. Solutions this allow direct calculation of product rate coefficient and age measurements morphology. Where can be estimated or scarps known age, method allows unknown ages scarps.
We have conducted a paleomagnetic study of sediment cores obtained from the Selenga prodelta region Lake Baikal, Russia. This record, which spans approximately last 84 kyr, contributes to better understanding nature geomagnetic field behavior in Siberia and is useful correlation dating tool. demonstrate that Baikal sediments are recording variations field. The directional record displays secular variation with excursion at 20 ka additional excursions appearing as large‐amplitude 41, 61, 67...
The modern water (both pre- and post-atmospheric nuclear testing) of most lakes has an anomalously old apparent radiocarbon age due to what is commonly referred as the “reservoir effect.” In contrast marine settings, this 14 C-offset phenomenon primarily caused by pre-aged carbon discharged rivers and/or groundwater. paper, a 2-component box model based on principle C mass balance in lake early diagenesis zone was formulated address relative importance terrestrial inputs, autochthonous...
Zhou, W., Yu, S.‐Y., Burr, G. S., Kukla, J., Jull, A. J. T., Xian, F., Xiao, Colman, S. M., H., Liu, Z. & Kong, X. 2010: Postglacial changes in the Asian summer monsoon system: a pollen record from eastern margin of Tibetan Plateau. Boreas , Vol. 39, pp. 528–539. 10.1111/j.1502‐3885.2010.00150.x. ISSN 0300‐9483. A new constrained by 32 AMS radiocarbon dates Hongyuan peatland Zoige Basin reveals long‐term dynamics an alpine wetland ecosystem on Plateau over last 13 500 years. Changes...