Phytoplankton Chlorophyll Distribution in the Eastern Canadian Arctic

The distribution of phytoplankton chlorophyll concentration in Jones Sound, Lancaster Sound, and Eastern Baffin Bay was studied during the period 16-27 August 1979, using continuous ship-based horizontal and vertical profiling and continuous aerial water colour measurements. These data are discussed in relation to physical data collected from the ship, and to infrared temperature measurements made from the aircraft and the TIROS series satellites. While the satellite and airborne remote sensing techniques are capable only of viewing the near-surface layer, they provided a much more detailed and synoptic coverage of this large area than was possible using a vessel alone. Together the three types of data provide a reasonably detailed picture of phytoplankton distribution which compares well with other physical oceanographic data. On average the chlorophyll standing crop was moderate (69 mg/sq m in the top 35 m, n=24) and comparable to that reported for other open-water arctic regions, but the phytoplankton were not evenly distributed vertically or geographically. In Jones Sound and Lancaster Sound where local ice melt reduced the surface water density, strong subsurface chlorophyll maxima (up to 18 mg/cu m in a 1 m thick layer) were observed in association with the pycnoline. At the mouths of these sounds and along the eastern coast of Devon, Bylot, and Baffin islands the phytoplankton distribution was more vertically homogeneous and closely linked to the physical structure of the Baffin Current. Highest pigment concentrations were associated with eddies or meanders in the current. It is possible that these localized pigment concentrations are one manifestation of "biological hotspots" which help feed the large populations of marine birds and mammals of the eastern Arctic.Key words: phytoplankton, chlorophyll, distribution, eastern Canadian Arctic, remote sensingMots clés: phytoplancton, chlorophylle, distribution, l'est de l'Arctique canadien, télédétectio

Turbulence in a free surface

We report an experimental and numerical study of turbulent fluid motion in a free surface. The flow is realized experimentally on the surface of a tank filled with water stirred by a vertically oscillating grid positioned well below the surface. Particles floating on the surface are used to visualize the flow. The effect of surface waves appears to be negligible. The flow is unconventional in that it is confined to two dimensions but does not have squared vorticity as a conservation law, that it is not divergence free and that it inherits scaling features of the mean square velocity differences S_2(R) and the vorticity fluctuations Omega(R) from the bulk 3-d turbulence.Comment: 4 pages, 4 Postscript figure

Giant pulses of pulsar radio emission

Review report of giant pulses of pulsar radio emission, based on our detections of four new pulsars with giant pulses, and the comparative analysis of the previously known pulsars with giant pulses, including the Crab pulsar and millisecond pulsar PSR B1937+21.Comment: Proceedings of the 363. WE-Heraeus Seminar on: Neutron Stars and Pulsars (Posters and contributed talks) Physikzentrum Bad Honnef, Germany, May.14-19, 2006, eds. W.Becker, H.H.Huang, MPE Report 291, pp.72-7