A5082945005- Geology and Paleoclimatology Research
- Methane Hydrates and Related Phenomena
- Geological Studies and Exploration
- Isotope Analysis in Ecology
- Marine and coastal ecosystems
- Geological Modeling and Analysis
- Geological formations and processes
- Marine and environmental studies
- Hydrocarbon exploration and reservoir analysis
- Geological and Geophysical Studies
- Arctic and Antarctic ice dynamics
- Marine Biology and Ecology Research
- Oceanographic and Atmospheric Processes
- Groundwater and Isotope Geochemistry
- Geological and Geochemical Analysis
- Pacific and Southeast Asian Studies
- Paleontology and Stratigraphy of Fossils
- Geophysics and Gravity Measurements
- earthquake and tectonic studies
- Pleistocene-Era Hominins and Archaeology
- Microbial Community Ecology and Physiology
- Climate variability and models
- Arctic and Russian Policy Studies
- Atmospheric and Environmental Gas Dynamics
- Geomagnetism and Paleomagnetism Studies
Dalhousie University
2016-2025
University of Göttingen
2011
Woods Hole Oceanographic Institution
2005
Abstract. The stable isotopes of nitrogen offer a unique perspective on changes in the cycle, past and present. However, presence multiple forms marine sediments can complicate interpretation bulk isotope measurements. Although large-scale global patterns seafloor δ15N have been shown to match process-based expectations, small-scale heterogeneity seafloor, or alterations isotopic signals during translation into subseafloor record, could obscure primary signals. Here, public database...
Abstract Foraminifera are ubiquitous marine protists that intracellularly accumulate phosphate 1 , an important macronutrient in ecosystems and fertilizer potentially leaked into the ocean. Intracellular concentrations can be 100–1,000 times higher than surrounding water . Here we show storage foraminifera is widespread, from tidal flats to deep sea. The total amount of intracellular stored benthic foraminifer Ammonia confertitesta Wadden Sea during a bloom as high around 5% annual...
Radiocarbon age relationships between co‐occurring planktic foraminifera, alkenones, and total organic carbon in sediments from the continental margins of southern Chile, northwest Africa, South China Sea were compared with published results Namibian margin. Age sediment components are site‐specific relatively constant over time. Similar to slope, where alkenones have been reported be 1000–4500 years older than significantly (∼1000 years) foraminifera Chilean margin sediments. In contrast,...
The open subarctic Pacific is, at present, a high nitrate low chlorophyll (HNLC) region, where is perennially abundant the surface. Theoretically, HNLC status of this region subject to modification by ocean circulation and/or micronutrient supply, with implications for effectiveness biological pump and hence carbon sequestration in interior. Records biogenic detritus sediments from throughout indicate that export production was generally lower during glacial maxima, while nitrogen isotope...
On the basis of normalization to phosphate, a significant amount nitrate is missing from deep Bering Sea (BS). Benthic denitrification has been suggested previously be dominant cause for BS deficit. We measured water column 15 N/ 14 N and 18 O/ 16 O as integrative tracers microbial denitrification, together with pore water‐derived benthic fluxes in basin, order gain new constraints on mechanism fixed nitrogen loss BS. The lack any isotope enrichment into part supports hypothesis. deficit...
Abstract The metamorphic conditions and the age of thermal overprint were determined in metapelites, metaarenites metabasites Tethyan Himalayan Sequence (THS) SE Tibet using Kübler Index vitrinite reflectance data applying thermobarometrical (Thermocalc PERPLEX) geochronological methods (illite/muscovite K–Ar zircon apatite (U–Th)/He chronology). multiple folded thrust pile experienced a reaching locally peak between diagenetic stage ( c . 170 °C) amphibolite facies 600 °C at 10 kbar)....
Abstract The progress of science is tied to the standardization measurements, instruments, and data. This especially true in Big Data age, where analyzing large data volumes critically hinges on being standardized. Accordingly, lack community‐sanctioned standards paleoclimatology has largely precluded benefits advances field. Building upon recent efforts standardize format terminology paleoclimate data, this article describes Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced...
The abundance, distribution, and size of marine species are linked to temperature nutrient regimes profoundly affected by humans through exploitation climate change. Yet little is known about long-term historical links between ocean environmental changes resource abundance provide context for current potential future trends inform conservation management. We synthesize >4000 years ecosystem dynamics in a Northwest Atlantic region currently undergoing rapid changes, the Gulf Maine Scotian...
Significant uncertainties persist in the reconstruction of past sea surface temperatures eastern equatorial Pacific, especially regarding amplitude glacial cooling and details post‐glacial warming. Here we present first regional calibration alkenone unsaturation sediments versus mean annual (maSST). Based on 81 new 48 previously published data points, it is shown that open ocean samples conform to established global regressions U 37 K′ maSST there no systematic bias from seasonality...
Abstract A significant reduction in the Atlantic Meridional Overturning Circulation and rapid northern Hemisphere cooling 8200 years ago have been linked to final melting of Laurentide Ice Sheet. Although many studies associated this cold event with drainage Lake Agassiz-Ojibway, recent model simulations shown that Hudson Bay Saddle collapse would had much larger effects on than lake outburst itself. Based a combination Mg/Ca oxygen isotope ratios benthic foraminifera, study presents first...
Abstract The oceanic nitrogen cycle is critically important for the partitioning of greenhouse gases between ocean and atmosphere. Baffin Bay connects regions that are major sources (North Atlantic) sinks Pacific western Arctic) biologically available further harbors supersaturation nitrous oxide a coincident deficit in nitrate deep basin. Isotopic tracer profiles both species presented here provide novel insights into origin cycling reactive Bay, highlighting connectivity different Arctic...
We have measured 230 Th‐normalized opal fluxes in several cores from the eastern equatorial Pacific (EEP) to test validity of “silica leakage” hypothesis, which purports that redistribution silicic acid Southern Ocean low latitudes was responsible for a significant portion reduction atmospheric carbon dioxide (CO 2 ) during last glacial period. The silica leakage hypothesis predicts higher EEP and lower periods CO . These predictions are not borne by sedimentary record oxygen isotope stage...
The dependence on the mean climate state of response Atlantic meridional overturning circulation (AMOC) is investigated in 17 increasing greenhouse gas experiments with different initial conditions. AMOC declines all by 15% to 31%, typically largest those strongest AMOC. In cases, changes surface heat fluxes, rather than freshwater are dominant cause for transient decrease. Surface fluxes actually switch from reducing decrease, low values atmospheric CO 2 , reinforcing higher . addition, we...
We present new alkenone‐based sea surface temperature (SST) estimates from the eastern equatorial Pacific (EEP) for last 30 kyr. By combining these results with recently published records region, we reconstruct spatial pattern of changes in SST during Last Glacial Maximum (LGM). Alkenone‐based show a greater glacial cooling upwelling environment cold tongue than sites located further north front and Warm Pool. This result agrees paradigm stronger winds, increased upwelling, steeper zonal...
The clear predictions of the silicic acid leakage hypothesis (SALH) resulted in a number studies downcore opal records from tropical Pacific. original SALH predicts that unused acid, due to Fe‐driven changes Si versus N limitation, escaped glacial Southern Ocean equatorial upwelling regimes where it enhanced diatom productivity, thereby decreasing coccolith growth and lowering atmospheric CO 2 . In contrast predictions, however, sedimentary eastern Pacific (EEP) do not show burial during...