Woods Hole Oceanographic Institution

About: Woods Hole Oceanographic Institution is a nonprofit organization based out in Falmouth, Massachusetts, United States. It is known for research contribution in the topics: Population & Mantle (geology). The organization has 5685 authors who have published 18396 publications receiving 1202050 citations. The organization is also known as: WHOI.

Microbial diversity of hydrothermal sediments in the Guaymas Basin: evidence for anaerobic methanotrophic communities.

Abstract: Microbial communities in hydrothermally active sediments of the Guaymas Basin (Gulf of California, Mexico) were studied by using 16S rRNA sequencing and carbon isotopic analysis of archaeal and bacterial lipids The Guaymas sediments harbored uncultured euryarchaeota of two distinct phylogenetic lineages within the anaerobic methane oxidation 1 (ANME-1) group, ANME-1a and ANME-1b, and of the ANME-2c lineage within the Methanosarcinales, both previously assigned to the methanotrophic archaea The archaeal lipids in the Guaymas Basin sediments included archaeol, diagnostic for nonthermophilic euryarchaeota, and sn-2-hydroxyarchaeol, with the latter compound being particularly abundant in cultured members of the Methanosarcinales The concentrations of these compounds were among the highest observed so far in studies of methane seep environments The delta-(13)C values of these lipids (delta-(13)C = -89 to -58 per thousand) indicate an origin from anaerobic methanotrophic archaea This molecular-isotopic signature was found not only in samples that yielded predominantly ANME-2 clones but also in samples that yielded exclusively ANME-1 clones ANME-1 archaea therefore remain strong candidates for mediation of the anaerobic oxidation of methane Based on 16S rRNA data, the Guaymas sediments harbor phylogenetically diverse bacterial populations, which show considerable overlap with bacterial populations of geothermal habitats and natural or anthropogenic hydrocarbon-rich sites Consistent with earlier observations, our combined evidence from bacterial phylogeny and molecular-isotopic data indicates an important role of some novel deeply branching bacteria in anaerobic methanotrophy Anaerobic methane oxidation likely represents a significant and widely occurring process in the trophic ecology of methane-rich hydrothermal vents This study stresses a high diversity among communities capable of anaerobic oxidation of methane

Long Nonlinear Internal Waves

Abstract: Over the past four decades, the combination of in situ and remote sensing observations has demonstrated that long nonlinear internal solitary-like waves are ubiquitous features of coastal oceans. The following provides an overview of the properties of steady internal solitary waves and the transient processes of wave generation and evolution, primarily from the point of view of weakly nonlinear theory, of which the Korteweg-de Vries equation is the most frequently used example. However, the oceanographically important processes of wave instability and breaking, generally inaccessible with these models, are also discussed. Furthermore, observations often show strongly nonlinear waves whose properties can only be explained with fully nonlinear models.

Biogeochemistry of Stable Carbon Isotopes

Abstract: In 1947, in his classical paper on the thermodynamic properties of isotopic substances, H. C. Urey [1] laid the foundation of modern isotope geochemistry. At the same time, A. O. Nier [2] designed a new mass spectrometer which allowed the measurement of small differences in isotope abundance ratios. A modification in the Nier-type mass spectrometer and a refinement in instrumentation techniques by McKinney et al. [3] finally initiated stable isotope studies of the type that will be discussed in this review.

Deep-sea paleotemperature record of extreme warmth during the Cretaceous

Abstract: Oxygen isotope analyses of well-preserved foraminifera from Blake Nose (30°N paleolatitude, North Atlantic) and globally distributed deep-sea sites provide a long-term paleotemperature record for the late Albian–Maastrichtian interval that is difficult to reconcile with the existence of significant Cretaceous ice sheets. Given reasonable assumptions about the isotopic composition of Cretaceous seawater, our results suggest that middle bathyal water temperatures at Blake Nose increased from ∼12 °C in the late Albian through middle Cenomanian to a maximum of 20 °C during the latest Cenomanian and earliest Turonian. Bottom waters were again ∼12 °C during the middle Campanian and cooled to a minimum of 9 °C during the Maastrichtian. Correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from Blake Nose. Comparison of global bottom-water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late Albian through late Cenomanian to a hot greenhouse phase during the latest Cenomanian through early Campanian, then to cool greenhouse conditions during the mid-Campanian through Maastrichtian.

Evidence for enhanced mixing over rough topography in the abyssal ocean

Abstract: The overturning circulation of the ocean plays an important role in modulating the Earth's climate. But whereas the mechanisms for the vertical transport of water into the deep ocean--deep water formation at high latitudes--and horizontal transport in ocean currents have been largely identified, it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished. Turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise. However, measurements of the internal wave field, the main source of energy for mixing, and of turbulent dissipation rates, have typically implied diffusivities across surfaces of equal density of only approximately 0.1 cm2 s(-1), too small to account for the return flow. Here we report measurements of tracer dispersion and turbulent energy dissipation in the Brazil basin that reveal diffusivities of 2-4 cm2 s(-1) at a depth of 500 m above abyssal hills on the flank of the Mid-Atlantic Ridge, and approximately 10 cm2 s(-1) nearer the bottom. This amount of mixing, probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry, may be large enough to close the buoyancy budget for the Brazil basin and suggests a mechanism for closing the global overturning circulation.