A5086989297- Geology and Paleoclimatology Research
- Aquatic Ecosystems and Biodiversity
- Isotope Analysis in Ecology
- Aquatic Ecosystems and Phytoplankton Dynamics
- Tree-ring climate responses
- Pleistocene-Era Hominins and Archaeology
- Climate variability and models
- Geological formations and processes
- Archaeology and ancient environmental studies
- Marine and environmental studies
- Marine and coastal ecosystems
- Fish Biology and Ecology Studies
- Fish Ecology and Management Studies
- Water Quality and Resources Studies
- Hydrology and Sediment Transport Processes
- Rangeland Management and Livestock Ecology
- Fish biology, ecology, and behavior
- Geological Modeling and Analysis
- Tropical and Extratropical Cyclones Research
- American Environmental and Regional History
- Archaeology and Natural History
- Cryospheric studies and observations
- Climate Change, Adaptation, Migration
- Evolutionary Game Theory and Cooperation
- Archaeology and Rock Art Studies
Paul Smith's College
2013-2024
University of South Dakota
2018
University of Maine
2005-2013
University of New Hampshire
1997
Duke University
1985-1986
Although the dramatic climate disruptions of last glacial period have received considerable attention, relatively little has been directed toward variability in Holocene (11,500 cal yr B.P. to present). Examination ?50 globally distributed paleoclimate records reveals as many six periods significant rapid change during time 9000"8000, 6000"5000, 4200"3800, 3500"2500, 1200"1000, and 600"150 Most events these are characterized by polar cooling, tropical aridity, major atmospheric circulation...
An extreme megadrought occurred in the Afro-Asian monsoon region during an iceberg melting episode 50,000 years ago.
Paleoclimatic records from equatorial East Africa, Antarctica, and Greenland reveal that atmospheric circulation changed abruptly at the early to mid-Holocene transition full postglacial conditions. A climatic reorganization occurred all three sites between 8200 7800 years ago lasted 200 or less appears have been related abrupt transitions in both marine terrestrial around world.
Abstract Fine-interval (∼30–45 yr) sampling of a core from Lake Victoria's Damba Channel shows that numerous abrupt changes in the lake's diatom assemblages have occurred response to climatic fluctuations over past 11,400 14 C yr. Four distinct phases bounded by sudden transitions are inferred: (1) variably dry ∼11,400–10,000 yr B.P., (2) humid ∼10,000–7200 (3) more seasonal ∼7200–2200 and (4) arid ∼2200–0 with “Little Ice Age” event ∼600–200 B.P. The diatom-inferred paleoclimatic history...
Abstract A new diatom record from Lake Victoria’s Pilkington Bay, subsampled at 21- to 25-year intervals and supported by 20 AMS dates, reveals a ∼10,000 calendar year environmental history that is published pollen data two nearby sites. With their chronologies adjusted here account for newly documented ancient carbon effects in the lake, these three records provide coherent, finely resolved reconstruction of Holocene climate change equatorial East Africa. After an insolation-induced...
Abstract. The austral westerlies strongly influence precipitation and ocean circulation in the southern temperate zone, with important consequences for cultures ecosystems. Global climate models anticipate poleward retreat of future warming, but available paleoclimate records that might test these have been limited to South America New Zealand, are not fully consistent each other may be complicated by influences from climatic factors. Here we present first high-resolution diatom...
Abstract The evolution of the El Niño-Southern Oscillation (ENSO) during Holocene remains uncertain. In particular, a host new paleoclimate records suggest that ENSO internal variability or other external forcings may have dwarfed fairly modest response to precessional insolation changes simulated in climate models. Here, using fully coupled ocean-atmosphere model simulations, we show accounting for vegetated and less dusty Sahara mid-Holocene relative preindustrial can reduce by 25%, more...
Significance Our modeling study shows the crucial role of vegetation cover over Sahara and reduced dust emission in altering tropical cyclone activity during mid-Holocene (6,000 yBP). results also demonstrate how these regional changes land are able to affect areas far afield through large-scale atmospheric circulation. strongly suggests that an appropriate representation is paramount importance be capture past—and potentially future—climate changes.
SUMMARY. 1. Microfossil and X‐ray analyses of sediment cores from Lake Victoria. East Africa, reveal a history dramatically shifting environmental conditions over the last 25,000 years. 2. The diatom record 10 m core collected beneath 66 water at an offshore station extends known lake 10,000 years beyond published records Pilkington Bay Damba Channel, shows that maximal late Pleistocene aridity occurred between 15,000 13,000 bp . Lack precipitated carbonates in sediments suggests remained...
An association of high sunspot numbers with rises in the level Lake Victoria, East Africa, has been focus many investigations and vigorous debate during last century. In this paper, we show that peaks ∼11‐year cycle were accompanied by Victoria maxima throughout 20th century, due to occurrence positive rainfall anomalies ∼1 year before solar maxima. Similar patterns also occurred at least five other African lakes, which indicates these sunspot‐rainfall relationships broadly regional scale....
AbstractABSTRACT. Although considerable attention has been paid to the record of temperature change over last few centuries, range and rate atmospheric circulation hydrology remain elusive. Here, eight latitudinally well‐distributed (pole‐equator‐pole), highly resolved (annual decadal) climate proxy records are presented that demonstrate major changes in these variables 2000 years. A comparison between 14C demonstrates a first‐order relationship variable Sun climate. The is seen on global scale.
Abstract The location and intensity of the austral westerlies strongly influence southern hemisphere precipitation heat transport with consequences for human society ecosystems. With future warming, global climate models project increased aridity in mid‐latitudes related to continued poleward contraction westerlies. We utilize Antarctic ice cores investigate past set stage prediction behaviour show that Holocene West core reconstructions atmospheric circulation sensitively record naturally...
Sediment and microfossil analyses of a 7.5-m core from Lake Cheshi suggest that south-central Africa experienced late Quaternary climate changes similar to those in East Africa. The lake formed around 34,000 yr B.P., after prelacustrine phase at least 6000 yr, climatic or tectonic causes. Ratios precipitation evaporation were probably today until decline about 15,000–13,000 B.P. when the shrank became chemically concentrated. Maximal levels occurred between 8000 4000 followed by low stand...
Abstract A nearshore core (LT03-05) from the north basin of Lake Tanganyika provides diatom, pollen, and sedimentary time series covering last ca. 3800 yr at 15–36 resolution. chronology supported by 21 AMS dates on terrestrial lacustrine materials allows us to account for ancient carbon effects 14 C ages propose refinements region's climatic history. Conditions drier than those today were followed after 3.30 ka an overall wetting trend. Several century-scale climate variations superimposed...