Giant amphipod from the abyssal pacific ocean

A baited camera has recorded a lysianassid amphipod that is twice as large as the largest amphipod previously recorded. The locality for this mobile omnivore is the sterile bottom of the eastern North Pacific Ocean, at a depth of 5304 meters.     

Enhanced diapycnal mixing by salt fingers in the thermocline of the tropical Atlantic

Diapycnal mixing plays a significant role in the ocean's circulation and uptake of heat and carbon dioxide, but has not been quantified in salt finger-driven thermohaline staircases. We recently performed a tracer release experiment in the western tropical Atlantic staircase at approximately 400 m depth. The observed dispersion implies an effective diapycnal diffusivity for tracer and salt of 0.8 to 0.9 x 10(-4) m2/s. Temperature microstructure data interpreted in terms of a vertical production-dissipation balance yields a smaller effective diffusivity for heat of 0.45 (+/- 0.2) x 10(-4) m2/s, consistent with salt fingers and well above the mixing ascribable to mechanical turbulence.     

Ocean science. Enhanced: internal tides and ocean mixing

Recent satellite and in situ observations have shown that at ocean ridges and other seafloor topographic features, a substantial amount of energy is transferred from the main ocean tides into "internal tides." In his Perspective, Garrett explains how these internal waves with tidal periods propagate through the density-stratified deep ocean and eventually break down into turbulence. The resulting mixing affects ocean stratification and ocean circulation. It thus influences climate as well as biological production. The energy for the internal tides is derived from the rotational energy of the Earth-Moon system changes of the length of the day and the distance to the Moon.     

Climate response times: dependence on climate sensitivity and ocean mixing

The factors that determine climate response times were investigated with simple models and scaling statements. The response times are particularly sensitive to (i) the amount that the climate response is amplified by feedbacks and (ii) the representation of ocean mixing. If equilibrium climate sensitivity is 3 degrees C or greater for a doubling of the carbon dioxide concentration, then most of the expected warming attributable to trace gases added to the atmosphere by man probably has not yet occurred. This yet to be realized warming calls into question a policy of "wait and see" regarding the issue of how to deal with increasing atmospheric carbon dioxide and other trace gases.     

Fossil deep-sea channel on the aleutian abyssal plain

The discovery of a leveed deep-sea channel whose axial gradient reverses near the Aleutian trench supports the hypothesis that the downbowing of the trench interrupted the turbidity current processes that constructed the Aleutian abyssal plain.     

Teleconnections in the equatorial pacific ocean

Geostrophic water transport by the equatorial countercurrent is compared with the observed sea level difference between two pairs of islands situlated north and south of the current. The high correlation between the transport and the sea level difference makes it possible to construct a time series for the countercurrent transport over a 21-year period. The countercurrent carries warm water into the eastern tropical Pacific, and fluctuations in its strength give rise to temperature anomalies off Central America. Periods of exceptionally high transport by the countercurrent in the western Pacific coincide with the occurrence of El Ni?o several thousand kilometers downstream and demonstrate the existence of teleconnections between events in the Pacific Ocean.     

Autotrophic picoplankton in the tropical ocean

In phytoplankton of the eastern tropical Pacific Ocean from 25 to 90 percent of the biomass (measured as chlorophyll a) and 20 to 80 percent of the inorganic carbon fixation were attributable to particles that could pass a screen with a 1-micrometer pore diameter. Evidence is presented that these are indeed autotrophic cells and not cell fragments.     

Thermal stratification in the arctic ocean

Fine scale measurements of the vertical temperature profile in an Arctic water column show the presence of several cascaded isothermal layers. Layers between the depths of 300 anid 350 meters range from 2 to 10 meters in thickness, while the temperature change between adjacent layers is approximately 0.026 degrees C. The individual layers are isothermal to within +/- 0.001 degrees C.     

Monoplacophora in the South atlantic ocean

Occurrence of Neopilina off the southeastern tip of South America may indicate rather widespread distribution of this abyssal group, under favorable conditions, throughout the seas of the world.     

Three-dimensional flow in the upper ocean

Measurements made from the Research Platform FLIP provide some of the first direct observations of three-dimensional flow within the surface mixed layer of the ocean. Relatively narrow regions of downwelling flow were found within the mixed layer, in coincidence with bands of convergent surface flow. At mid-depth in the mixed layer, the downwelling flow had magnitudes of up to 0.2 meter per second and was accompanied by a downwind, horizontal jet of comparable magnitude. There is some evidence that these motions transport heat and phytoplankton within the mixed layer.     

Orphan strontium-87 in abyssal peridotites: daddy was a granite

The (87)Sr/(86)Sr ratios in some bulk abyssal and alpine peridotites are too high to be binary mixtures of depleted mantle and seawater components. The apparent excess, or "orphan," (87)Sr appears to be separated from its radioactive parent. Such observations were widely held to be analytical artifacts. Study of several occurrences of orphan (87)Sr shows that the orphan component in abyssal peridotite is located in the alteration products of olivine and enstatite in the peridotite. The orphan (87)Sr is most likely introduced by infiltration of low-temperature (<200 degrees C) seawater bearing suspended detrital particulates. These particulates include grains of detrital clay that are partly derived from continental (that is, granitic) sources and thus are highly radiogenic. Orphan (87)Sr and other radiogenic isotopes may provide a tracer for low-temperature seawater penetrating into the oceanic crust.