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.

Evidence from Fram Strait (78° N) for early deglaciation

Abstract: Recent syntheses of the history of the last Northern Hemisphere glaciation and deglaciation illustrate that understanding of the mechanisms and timing of deglaciation before approximately 12,000 years BP1–5 is limited. After 12,000 yr BP, however, there is sufficient evidence from radiocarbon-dated moraines, raised beaches, varved lake sediments and pollen records to provide a reasonable temporal and geographic picture of the decay of the ice sheets. Here we report on the first oxygen isotope record from the Norwegian-Greenland Sea that is radiocarbon-dated directly by accelerator mass spectrometry. A significant light-oxygen-isotope event is recorded at approximately 15,000 years BP which suggests that the marine-based Barents Shelf ice sheet disintegrated rapidly at this time. Recent studies6,7 have estimated that the decay of this ice sheet could have contributed as much as 15 metres to eustatic sea-level rise. The decay of the Barents Shelf ice sheet is the earliest major deglacial event yet dated, and may have triggered subsequent deglacial events through eustatic sea-level effects.

Cobalt limitation and uptake in Prochlorococcus

Abstract: Processes that enable marine phytoplankton to acquire trace metals are fundamental to our understanding of primary productivity and global carbon biogeochemical cycling. Here we show that the abundant marine cyanobacterium, Prochlorococcus strain MED4-Ax, has an absolute cobalt requirement and that zinc cannot substitute for cobalt in the growth medium, as is the case in some other phytoplankton species. When resuspended into fresh medium, uptake of cobalt into the cell occurs as free cobalt (Co 21 ). In contrast, cultures augmented with conditioned medium assimilated cobalt significantly faster than those in fresh medium, leading to the hypothesis that Prochlorococcus produced organic cobalt ligands in the conditioned medium. This work suggests that the availability of cobalt might influence the composition of phytoplankton assemblages in the open ocean.

Interior pathways of the North Atlantic meridional overturning circulation

Abstract: To understand how our global climate will change in response to natural and anthropogenic forcing, it is essential to determine how quickly and by what pathways climate change signals are transported throughout the global ocean, a vast reservoir for heat and carbon dioxide. Labrador Sea Water (LSW), formed by open ocean convection in the subpolar North Atlantic, is a particularly sensitive indicator of climate change on interannual to decadal timescales. Hydrographic observations made anywhere along the western boundary of the North Atlantic reveal a core of LSW at intermediate depths advected southward within the Deep Western Boundary Current (DWBC). These observations have led to the widely held view that the DWBC is the dominant pathway for the export of LSW from its formation site in the northern North Atlantic towards the Equator. Here we show that most of the recently ventilated LSW entering the subtropics follows interior, not DWBC, pathways. The interior pathways are revealed by trajectories of subsurface RAFOS floats released during the period 2003-2005 that recorded once-daily temperature, pressure and acoustically determined position for two years, and by model-simulated 'e-floats' released in the subpolar DWBC. The evidence points to a few specific locations around the Grand Banks where LSW is most often injected into the interior. These results have implications for deep ocean ventilation and suggest that the interior subtropical gyre should not be ignored when considering the Atlantic meridional overturning circulation.

Discrete Transitions in Turbulent Convection

Abstract: The convection in a fluid between horizontal conducting surfaces is a very simple example of thermal turbulence, for the mean heat transport is independent of position while the distance between these surfaces is the only geometric parameter. This paper describes measurements of the heat transport and mean velocity in such convection up to Rayleigh numbers of 10 10 . Six discrete transitions in the slope of the heat-transport curve were observed between Rayleigh numbers of 1700 and 1000000. Although the thermal gradients vary by an order of magnitude from a boundary to the mid-regions of the fluid, these transitions appear to agree with those deduced on an assumption of a constant thermal gradient. Various visual observations of the fluctuating velocity field are also reported. Additional vertical barriers in the fluid markedly influence the horizontal flow but have negligible effect on the heat transport. This apparent lack of uniqueness of the flow patterns associated with a given heat transport suggests a new approach to turbulent phenomena discussed in a following theoretical paper.