A5071902308- Geology and Paleoclimatology Research
- Methane Hydrates and Related Phenomena
- Isotope Analysis in Ecology
- Paleontology and Stratigraphy of Fossils
- Geological formations and processes
- Hydrocarbon exploration and reservoir analysis
- Pleistocene-Era Hominins and Archaeology
- Marine and environmental studies
- Geological and Geophysical Studies
- Evolution and Paleontology Studies
- Marine and coastal ecosystems
- Geological Studies and Exploration
- Non-Destructive Testing Techniques
- Geomagnetism and Paleomagnetism Studies
- Drilling and Well Engineering
- Oceanographic and Atmospheric Processes
- Geochemistry and Geologic Mapping
- Infrastructure Maintenance and Monitoring
- Water Quality Monitoring and Analysis
- Geological and Geophysical Studies Worldwide
- Marine Biology and Ecology Research
- Reservoir Engineering and Simulation Methods
- Geological and Geochemical Analysis
- Atmospheric and Environmental Gas Dynamics
- Climate variability and models
Brown University
2016-2025
John Brown University
2010-2024
University of Freiburg
2021
Planetary Science Institute
2021
University of Hong Kong
2009
University of California, Santa Cruz
2009
Yale University
2009
Chinese University of Hong Kong
2009
Lafayette College
2009
Justus-Liebig-Universität Gießen
2001
Abstract The last interglacial, commonly understood as an interval with climate warm or warmer than today, is represented by marine isotope stage (MIS) 5e, which a proxy record of low global ice volume and high sea level. It arbitrarily dated to begin at approximately 130,000 yr B.P. end 116,000 the onset early glacial unit MIS 5d. age determined correlation uranium–thorium dates raised coral reefs. most detailed interglacial found in Vostok core where temperature reached current levels...
Birth of the Cool Over past 4 million years or so, tropical sea surface temperatures have experienced a cooling trend (see Perspective by Philander ). Herbert et al. (p. 1530 ) analyzed temperature records 3.5 from low-latitude sites spanning world's major ocean basins in order to determine timing and magnitude that has accompanied intensification Northern Hemisphere ice ages since Pliocene. Martínez-Garcia 1550 found enigmatic eastern equatorial Pacific cold tongue, feature one might not...
A tropical Pacific climate state resembling that of a permanent El Niño is hypothesized to have ended as result reorganization the ocean heat budget ∼3 million years ago, time when large ice sheets appeared in high latitudes Northern Hemisphere. We report high-resolution alkenone reconstruction conditions heart eastern equatorial (EEP) cold tongue reflects combined influences changes thermocline, properties thermocline's source waters, atmospheric greenhouse gas content, and orbital...
The Pliocene warm interval has been difficult to explain. We reconstructed the latitudinal distribution of sea surface temperature around 4 million years ago, during early Pliocene. Our reconstruction shows that meridional gradient between equator and subtropics was greatly reduced, implying a vast poleward expansion ocean tropical pool. Corroborating evidence indicates Pacific contrast 32 degrees N evolved from approximately 2 C ago 8 today. pool evidently had enormous impacts on climate,...
We provide the first continuous, orbital‐resolution sea surface temperature (SST) record from high‐latitude North Atlantic, a region critical to understanding origin of Plio‐Pleistocene ice ages and proximal regions that became frequently glaciated after ∼2.7 Ma. analyzed sediments Ocean Drilling Program Site 982 over last 4 Ma for their alkenone unsaturation index compared this water signal benthic δ 18 O obtained same section. find while ocean temperatures were significantly warmer (∼6°C)...
Time series of alkenone unsaturation indices gathered along the California margin reveal large (4° to 8°C) glacial-interglacial changes in sea surface temperature (SST) over past 550,000 years. Interglacial times with SSTs equal or exceeding that Holocene contain peak abundances pollen redwood, distinctive component temperate rainforest northwest coast California. In region now dominated by Current, warmed 10,000 15,000 years advance deglaciation at each five glacial maxima. did not rise...
Holocene and latest Pleistocene oceanographic conditions the coastal climate of northern California have varied greatly, based upon high‐resolution studies (ca. every 100 years) diatoms, alkenones, pollen, CaCO 3 %, total organic carbon at Ocean Drilling Program (ODP) Site 1019 (41.682°N, 124.930°W, 980 m water depth). Marine proxies (alkenone sea surface temperatures [SSTs] %) behaved remarkably like Greenland Ice Sheet Project (GISP)‐2 oxygen isotope record during Bølling‐Allerod, Younger...
Changing Rains The water cycle of the western United States has varied dramatically across glacial cycles Pleistocene, possibly because changes in tracks storms that deliver moisture to region. Lyle et al. (p. 1629 ) present evidence from a collection Great Basin lakes which show levels rose over last 20,000 years transported tropical Pacific, not southward diversion westerly storm track. Furthermore, timing lake level highs shows progression south north does coincide with northward wet intervals.
[1] Orbital tuning, the process of fitting sedimentary cycles to orbital periodicities, can estimate with high resolution timing and duration key events in geological record. We formulate here tuning as inverse problem finding variation sedimentation rate that matches sediment periodicities. Instead obtaining a single best estimate, we apply Bayesian formulation define probability distribution variations result powerful By sampling this Monte Carlo method, quantify uncertainty inferred rates...
[1] The Bering Sea gateway between the Pacific and Arctic oceans impacts global climate when glacial-interglacial shifts in shore line position ice coverage change regional albedo. Previous work has shown that during last glacial termination into Holocene, sea level rises diminishes from perennial to absent. Yet, existing not quantified duration or surface temperatures (SST) this transition. Here we combine diatom assemblages with first alkenone record provide a semiquantitative of duration,...
Abstract Alkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since 1980s. However, alkenone-based SST reconstructions northern high latitude oceans show significant bias towards warmer temperatures core-tops, diverge from other proxies down core records, and often accompanied anomalously relative abundance of C 37 tetra-unsaturated methyl alkenone (%C 37:4 ). Elevated %C is widely interpreted as an...
The Miocene Climatic Optimum (MCO) from ~17 to 14 million years ago (Ma) represents an enigmatic reversal in Cenozoic cooling. A synthesis of marine paleotemperature records shows that the MCO was a local maximum global sea surface temperature superimposed on period at least 19 Ma 10 Ma, during which temperatures were order 10°C warmer than present. Our high-resolution reconstruction ocean crustal production, proxy for tectonic degassing carbon, suggests production rates ~35% higher modern...
The timing of ice ages over the past ∼2,600 thousand years (kyr) follows pacing by cyclical changes in three aspects Earth's orbit that influence solar energy received as a function latitude and season. Explaining large magnitude climate is challenging, particularly so across period time from ∼1,250 to 750 ka—the Mid-Pleistocene Transition or MPT. average repeat age cycles changed an earlier 41-kyr rhythm longer more intense glaciations at spacing about 100 kyr. this change very difficult...
We examine the causes of anoxia in regions such as Eastern Mediterranean, which have exchange over sills with adjacent basins. Box models show that concentration limiting nutrient is major determinant deep oxygen levels. The most effective way increasing concentrations to point where occurs change flow pattern across ventilating With a sill present Strait Sicily, it difficult obtain Mediterranean without also driving Western low and high Episodes are associated freshening surface waters. A...
We examine the hypothesis that global scale episodes of anoxia such as occurred in Cretaceous are due to high productivity and/or stagnation circulation. Two modes ocean circulation considered: a thermohaline overturning cell, essentially vertical, which involves upwelling into surface followed by sinking deep water formation regions; and an approximately horizontal cell connects abyss directly with deeply convecting waters regions. Modern analogs for these processes North Atlantic Deep...
An 8‐m section of a mid‐Cretaceous (Albian) deep‐sea sediment core from Piobbico, Italy contains ∼2 cycles/m compositional oscillations. As postdepositional chemical migration in the is weak, relative amount carbonate primary indicator Cretaceous paleoclimate variability. We report results spectral analysis two series, CaCO 3 wt % measurements taken at roughly 2 cm intervals and more densely sampled photodensitometer record light‐dark variation. The uncertainty age‐depth relation (i.e.,...