Cruise Summary Report RRS DISCOVERY D276

8 – 21 December 2003 Fortaleza / Brazil and Rio de Janeiro / Brazil The cruise was a German contribution to the CLIVAR programme. The intention was to build upon the data gathered during the World Ocean Circulation Experiment. The spreading of Antarctic Bottom Water in the South Atlantic is seen as an integral limb of the global thermohaline circulation. During the last 30 years, there has been a marked rise in bottom water temperature which is thought to be significantly relevant for climate change. It was the purpose of the cruise to deploy two subsurface moorings at the entrance of the Vema Channel. They are designed to monitor physical property fluctuations during the coming 16 months

Mathematical analysis of the photoelectric effect

We study the photoelectric effect on the example of a simplified model of an atom with a single bound state, coupled to the quantized electromagnetic field. For this model, we show that Einstein's prediction for the photoelectric effect is qualitatively and quantitatively correct to leading order in the coupling parameter. More specifically, considering the ionization of the atom by an incident photon cloud consisting of $N$ photons, we prove that the total ionized charge is additive in the $N$ involved photons. Furthermore, if the photon cloud is approaching the atom from a large distance, the kinetic energy of the ejected electron is shown to be given by the difference of the photon energy of each single photon in the photon cloud and the ionization energy.Comment: See also http://www.intlpress.com/ATM

Spreading of Antarctic Bottom Water in the Atlantic Ocean

This paper describes the transport of bottom water from its source region in the Weddell Sea through the abyssal channels of the Atlantic Ocean. The research brings together the recent observations and historical data. A strong flow of Antarctic Bottom Water through the Vema Channel is analyzed. The mean speed of the flow is 30 cm/s. A temperature increase was found in the deep Vema Channel, which has been observed for 30 years already. The flow of bottom water in the northern part of the Brazil Basin splits. Part of the water flows through the Romanche and Chain fracture zones. The other part flows to the North American Basin. Part of the latter flow propagates through the Vema Fracture Zone into the Northeast Atlantic. The properties of bottom water in the Kane Gap and Discovery Gap are also analyzed

The Mid-Ocean Dynamics Experiment

The Mid-Ocean Dynamics Experiment (MODE-1) was designed to investigate mid-ocean mesoscale eddies. An intensive and extensive program of measurements in three spatial dimensions and time was undertaken in an area southwest of Bermuda from March through mid-July 1973. Principal components of the experiment were an array of moored current meters and temperature-pressure recorders, hydrographic stations, drifting neutrally buoyant floats at 1500 m tracked by SOFAR, and acoustic and electromagnetic profilers. During MODE-1 a smaller scale survey relying on ship-tracked neutrally buoyant floats, a conductivity-temperature (CTD) survey, and a moored current meter array, MINIMODE, was carried out. The experiment was preceded by MODE-0, consisting of measurements by a series of moored current meters and other instruments in the general area selected for MODE-1. MODE-1 observations were generally within a 300-km radius circle centered at 26°N, 69° 40′W, with a greater concentration of observations in the interior of the circle. The region covers varied topography, with a flat a byssal plain sloping upward to the continental rise in the western half and rough topography in the eastern half. Descriptive, dynamical, numerical results of the experiment are presented. It is concluded that mid-ocean eddies are part of an energetic and structured variability field superimposed on the weaker gyre-scale mean circulation. In the western North Atlantic there is a band of eddy variability of around 100-day period and 70-km scale in which currents are horizontally nearly isotropic; vertical scales are of the order of the depth. The experiment provided conclusive evidence of the existence of mid-ocean eddies and serves as the basis for future experiments, such as POLYMODE, to extend our knowledge of these systems