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Surface And Deep Ocean Circulation In The Subpolar North Atlantic During The Mid-Pleistocene Revolution, Amy K. Wright, Benjamin P. Flower

Marine Science Faculty Publications

We investigated surface and deep ocean variability in the subpolar North Atlantic from 1000 to 500 thousand years ago (ka) based on two Ocean Drilling Program (ODP) sites, Feni drift site 980 (55°29′N, 14°42′W) and Bjorn drift site 984 (61°25′N, 24°04′W). Benthic foraminiferal stable isotope data, planktic foraminiferal faunas, ice‐rafted debris data, and faunally based sea‐surface temperature estimates help test the hypothesis that oceanographic changes in the North Atlantic region were associated with the onset of the 100‐kyr world during the mid‐Pleistocene revolution. Based on percentage of Neogloboquadrina pachyderma (s) records from both sites, surface waters during interglacials and glacials …

A Multiproxy Approach To Reconstructing Sea Surface Conditions Using Coral Skeleton Geochemistry, Terrence M. Quinn, Daniel E. Sampson

Marine Science Faculty Publications

[1] We use elemental ratio (Mg/Ca, Sr/Ca, U/Ca and Ba/Ca) and oxygen isotope data from a Porites lutea coral head collected from offshore Amedee Island, New Caledonia (22degrees29'S, 166degrees28'E) to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions. We have assessed the robustness of each geochemical proxy by comparing 25 years (1992-1968) of monthly geochemical variations with a local record of sea surface temperature (SST) and with the appropriate 1degrees by 1degrees grid box from a global gridded SST data set. We conclude from our comparison that the most consistent proxies of …

Volatiles In Basaltic Glasses From The Easter‐Salas Y Gomez Seamount Chain And Easter Microplate: Implications For Geochemical Cycling Of Volatile Elements, Kyla Simons, Jacqueline Dixon, Jean‐Guy Schilling, Richard Kingsley, Robert Poreda

Marine Science Faculty Publications

We present H₂O, CO₂, and Cl concentrations in 66 basaltic glasses from the Easter Microplate (EMP) and Easter‐Salas y Gomez Seamount Chain (ESC) system in the southeastern Pacific. The EMP‐ESC system is characterized by binary mixing between a depleted mid‐ocean ridge basalt (MORB) mantle source (DMM) and an incompatible element and radiogenic isotope enriched source, the Salas y Gomez mantle plume (SyG). Plume material is channeled toward the ridge crest centered at ∼27°S on the east rift of the microplate. Water concentrations on the EMP are highest on the east rift at ∼27°S and become progressively …

Satellite Images Track “Black Water” Event Off Florida Coast, South-West Florida Dark-Water Observations Group (Swfdog), Robert H. Weisberg, Chuanmin Hu

Marine Science Faculty Publications

A mass of dark water, at times exceeding 60 km in diameter and spinning slowly in a clockwise eddy, occupied most of the Florida Bight between January and March 2002, capturing the attention of fishermen, the public, and government agencies. The “black water,” as it was dubbed in the national and international press (for example, see http://www.naplesnews.com), was first reported by fishery pilots in the Florida Bight in January 2002. Fishermen reported that fish were not to be found in the black water and there were dead sponges in the vicinity, suggesting that the area could be a “dead zone” …

Drilling Reveals Climatic Consequences Of Tasmanian Gateway Opening, Neville Exon, Jim Kennett, Mitch Malone, Henk Brinkhuis, George Chaproniere, Atsuhito Ennyu, Patrick Fothergill, Michael Fuller, Marianne Grauert, Peter Hill, Amelia E. Shevenell

Marine Science Faculty Publications

One of the great stories of geoscience is how Gondwana broke up and the other southern continents drifted northward from Antarctica, which led to major changes in global climate.

The recent drilling of Ocean Drilling Project (ODP) Leg 189 addressed in detail what happened as Australia drifted away from Antarctica and the Tasmanian Gateway opened. The drifting contributed to the change in global climate, from relatively warm early Cenozoic “greenhouse” conditions to late Cenozoic “icehouse” conditions. It isolated Antarctica from warm gyral surface currents from the north and provided the critical deepwater conduits that eventually led to ocean conveyor circulation …

Antarctic Holocene Climate Change: A Benthic Foraminiferal Stable Isotope Record From Palmer Deep, Amelia E. Shevenell, James P. Kennett

Marine Science Faculty Publications

The first moderate‐ to high‐resolution Holocene marine stable isotope record from the nearshore Antarctic continental shelf (Ocean Drilling Program (ODP) Hole 1098B) suggests sensitivity of the western Antarctic Peninsula hydrography to westerly wind strength and El Niño‐Southern Oscillation (ENSO)‐like climate variability. Despite proximity to corrosive Antarctic water masses, sufficient CaCO₃ in Palmer Deep sediments exists to provide a high‐quality stable isotopic record (especially in the late Holocene). Coherence of benthic foraminifer δ¹⁸O, δ¹³C, sedimentologic, and CaCO₃ fluctuations suggests that rapid (years) Palmer Deep bottom water temperature fluctuations of 1°–1.5°C are associated with competitive interactions …

D/H Ratios In Basalt Glasses From The Salas Y Gomez Mantle Plume Interacting With The East Pacific Rise: Water From Old D‐Rich Recycled Crust Or Primordial Water From The Lower Mantle?, Richard Kingsley, Jean-Guy Schilling, Jacqueline E. Dixon, Peter Swart, Robert Poreda, Kyla Simons

Marine Science Faculty Publications

Deuterium/Hydrogen isotope ratios were measured in 22 fresh basalt glasses dredged from young seamounts along the Easter‐Salas y Gomez seamount chain (ESC) and from the spreading centers of the Easter Microplate (EMP). The δD values decrease regularly from −36‰ near Salas y Gomez to −63‰, 800 km west on the East Pacific Rise (EPR) and the west rift of the EMP. Similar gradients are observed in H₂O, Pb and Sr radiogenic isotope ratios, trace element concentrations, and in the ratios of incompatible to moderately incompatible trace elements. Fractionation of the D/H ratios by recent low‐temperature near surface processes …

Low-Frequency Variations In Global Mean Sea Level: 1950–2000, D. P. Chambers, C. A. Mehlhaff, T. J. Urban, D. Fujii, R. S. Nerem

Marine Science Faculty Publications

[1] Low-frequency variability in global mean sea level (GMSL) is studied for the period 1950–2000 by interpolating sparse tide gauge data to a global grid using empirical orthogonal functions (EOFs) of sea level variability determined from TOPEX/Poseidon (T/P) altimeter data. Results are based on data with long-term trends removed. The fact that the results do not have secular trends is an artifact of the analysis and should not be interpreted as an indication that sea level is not rising. The EOF reconstruction technique is discussed, and the resulting GMSL time series is compared to GMSL time series from Geosat and …

Correlated Geophysical, Geochemical, And Volcanological Manifestations Of Plume‐Ridge Interaction Along The Galápagos Spreading Center, R. S. Detrick, J. M. Sinton, G. Ito, J. P. Canales, M. Behn, T. Balcic, B. Cushman, Jacqueline E. Dixon, D. W. Graham, J. J. Mahoney

Marine Science Faculty Publications

As the Galápagos hot spot is approached from the west along the Galápagos Spreading Center there are systematic increases in crustal thickness and in the K/Ti, Nb/Zr, ³He/⁴He, H₂O, and Na₂O content of lavas recovered from the spreading axis. These increases correlate with progressive transitions from rift valley to axial high morphology along with decreases in average swell depth, residual mantle Bouguer gravity anomaly, magma chamber depth, average lava Mg #, Ca/Al ratio, and the frequency of point‐fed versus fissure‐fed volcanism. Magma chamber depth and axial morphology display a “threshold” effect in which …

Estimates Of Vertical Crustal Motion Derived From Differences Of Topex/Poseidon And Tide Gauge Sea Level Measurements, R. S. Nerem, G. T. Mitchum

Marine Science Faculty Publications

[1] We have computed estimates of the rate of vertical crustal motion from differences of sea level measurements made by the TOPEX/POSEIDON radar altimeter and a globally distributed network of 114 tide gauges. A rigorous error analysis was performed which suggests the accuracy of the estimated vertical rates is approximately 1–2 mm/year for roughly half of the tide gauges, which is sufficiently accurate to detect a variety of geophysical phenomena. While only a cursory analysis of the estimated crustal motion rates was performed, we observed many interesting phenomena including significant uplift at volcanic islands in the Pacific and uplift of …

U.S. Southern Ocean Global Ecosystems Dynamics Program, Eileen E. Hofmann, John M. Klinck, Dan P. Costa, Kendra L. Daly, Joseph J. Torres, William R. Fraser

Marine Science Faculty Publications

The first scientific exploration of the Antarctic dates to the end of the seventeenth century, when Sir Edmund Halley ventured just south of the Polar Front (about 60°S). During the following century, many scientific expeditions were undertaken to explore and describe the vast oceans surrounding the Antarctic continent. One of these expeditions, aboard the Belgian vessel, Belgica, provided the first winter scientific observations when it became beset in sea ice and spent the winter of 1898 drifting off the west coast of the Antarctic Peninsula. About fifteen years later, Sir Ernest Shackleton and his crew overwintered on Elephant Island, …

Hydrothermal Venting Along Earth's Fastest Spreading Center: East Pacific Rise, 27.5°–32.3°, E. T. Baker, R. N. Hey, J. E. Lupton, J. A. Resing, R. A. Feely, J. J. Gharib, G. J. Massoth, F. J. Sansone, M. Kleinrock, F. Martinez, D. F. Naar, C. Rodrigo, D. Bohnenstiehl, D. Pardee

Marine Science Faculty Publications

During March/April 1998 we conducted detailed mapping and sampling of hydrothermal plumes along six segments of Earth's fasting spreading mid-ocean ridge, 27.5°–32.3°S on the East Pacific Rise. We compared the distribution and chemistry of hydrothermal plumes to geological indicators of long-term (spreading rate) and moderate-term (ridge inflation) variations in magmatic budget. In this large-offset, propagating rift setting, these geological indices span virtually the entire range found along fast spreading ridges worldwide. Hydrothermal plumes overlaid ∼60% of the length of superfast (>130 km/Myr) spreading axis surveyed and defined at least 14 separate vent fields. We observed no plumes over the …

Intra-Annual Variation In The Stable Oxygen And Carbon And Trace Element Composition Of Sclerosponges, P. K. Swart, S. Thorrold, B. Rosenheim, A. Eisenhauer, C. G. A. Harrison, M. Grammer, C. Latkoczy

Marine Science Faculty Publications

[1] This paper presents data to support the presence of (1) intra-annual signals in the chemical composition (δ18O and Sr/Ca) of the skeletons of sclerosponges from the Bahamas and (2) variable rates of skeletal accretion. These conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 μm and a laser microprobe which obtained trace element data every 20 μm (Sr, Mg, and Pb). An age model was established using a combination of changes in the concentration of Pb, the …