Observations of Arctic Sea Ice Dynamics Using the Earth Resources Technology Satellite (ERTS-1)

This study shows that ERTS-l, launched by the U.S. National Aeronautics and Space Administration in July 1972, can be used to make synoptic observations of dynamic changes in arctic sea ice .... Each data swath of ERTS-l is 185 kilometres wide at the surface and is repeated once every 18 days. ... Because of a near-polar orbit, this sidelap increases to over 80 per cent at arctic latitudes. As a consequence of this large sidelap, the tracking of individual ice features for periods up to 5 or 6 days is permitted. The ERTS-1 Multispectral Scanner Subsystem (MSS) records data by simultaneously scanning across the satellite track in 4 spectral bands. The wavelength limits of the 4 bands are: green (0.5-0.6 µm), red (0.6-0.7 µm), and two near infrared bands (0.7-0.8 µm and 0.8-1.1 µm). The nominal spatial resolution for all 4 bands is 80 metres. A standard ERTS-1 photographic format has an image scale of nearly 1:1,000,000, which is convenient for direct comparison with available maps. Hendriksen Strait, the passage between Amund Ringnes Island and Cornwall Island at about 77°45' N and 95°00' W constituted the study area; it is in the Queen Elizabeth Islands of Arctic Canada, and is one of the most enticing and promising areas of recent oil and gas strikes. ... during a 6-day period from 23 to 28 August, ERTS-1 provided 5 days of coverage of Hendriksen Strait. Various types of sea ice can be identified in the ERTS-l imagery (0.6-0.7 µm band) .... In such a sequence of observations, a number of sea ice changes with time are detectable. Changes in position of individual ice floes can easily be translated to velocity. A number of ice floes were tracked over the 5-day period and their velocities calculated. The average velocity for ice floe movement was 8.5 kilometres/day .... ERTS-l can be used to study ice floe morphology and dynamics in the Beaufort Sea at time scales of several days to months. Repeated observations of individual ice floes such as those available here will also allow calculation of the ablation of the ice mass, in this case the decrease of surface area with time. ... The ice cover, i.e. the relative amount of sea ice present in a given area, is important for shipping purposes and air-sea interaction processes. The ice cover in Hendriksen Strait on 23 August was approximately 7/10, decreasing to 2/10 by 28 August. This type of sea ice change is easily observed from ERTS-1 .... In regard to the delineation of navigation routes through sea ice, the detection of active melting on the surface of the ice would indicate areas likely to be ice free in the near future. ERTS-1 has the ability to do this through observations of reflectance variability both temporally and spectrally. The second method of observing the sea ice reflectance change is provided by comparing two separate images made at the same time but in different spectral bands. ... Because the absorption of solar radiation by water is much greater in the near infrared than in the visible portion of the spectrum, the lower reflectance is again probably due to the presence of melt-water on the surface of the ice. Thus sea ice with water on it, even in very thin layers, will show a considerable difference in reflectance between these spectral bands of observation. ... Temporal and spectral observations of reflectance variations afforded by ERTS-l thus make it possible to locate areas of sea ice that are in varying stages of melting and breakup. The results presented here demonstrate that for high latitudes, ERTS-1 will provide overlapping coverage on sequential days that will allow observation of dynamic changes in the polar regions. In addition, route planning for shipping in the Arctic should benefit from frequent observations of sea ice movement and reflectance variations of the type obtainable from ERTS-l. Projected further, sea ice observations from ERTS-l over a period of years in the Arctic Islands should aid in the placement of offshore oil-drilling structures. Reflectance measurements over this period will also increase our understanding of the heat balance in the polar regions. Finally, ERTS-l observations of the amount of ice cover versus the amount of open water will be important in determining boundary conditions for future use in models of the global heat balance

Ecology and Biogeography of Free-Living Nematodes Associated with Chemosynthetic Environments in the Deep Sea: A Review

Background: Here, insight is provided into the present knowledge on free-living nematodes associated with chemosynthetic environments in the deep sea. It was investigated if the same trends of high standing stock, low diversity, and the dominance of a specialized fauna, as observed for macro-invertebrates, are also present in the nematodes in both vents and seeps. Methodology: This review is based on existing literature, in combination with integrated analysis of datasets, obtained through the Census of Marine Life program on Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss). Findings: Nematodes are often thriving in the sulphidic sediments of deep cold seeps, with standing stock values ocassionaly exceeding largely the numbers at background sites. Vents seem not characterized by elevated densities. Both chemosynthetic driven ecosystems are showing low nematode diversity, and high dominance of single species. Genera richness seems inversely correlated to vent and seep fluid emissions, associated with distinct habitat types. Deep-sea cold seeps and hydrothermal vents are, however, highly dissimilar in terms of community composition and dominant taxa. There is no unique affinity of particular nematode taxa with seeps or vents. Conclusions: It seems that shallow water relatives, rather than typical deep-sea taxa, have successfully colonized the reduced sediments of seeps at large water depth. For vents, the taxonomic similarity with adjacent regular sediments is much higher, supporting rather the importance of local adaptation, than that of long distance distribution. Likely the ephemeral nature of vents, its long distance offshore and the absence of pelagic transport mechanisms, have prevented so far the establishment of a successful and typical vent nematode fauna. Some future perspectives in meiofauna research are provided in order to get a more integrated picture of vent and seep biological processes, including all components of the marine ecosystem

An investigation of evaporation from the ocean off the Oregon coast, and from Yaquina Bay, Oregon

A weather station was established on the dock of the Oregon State University Marine Science Center, Yaquina Bay, Oregon. A total of 197 weather observations was made from 30 June 1966 to 23 September 1966, with emphasis on the determination of the rate of evaporation from an evaporation pan and from atmometers. Sources of observational error were investigated and corrections applied as necessary. The daily variation in evaporation was determined. The correlation between wind, vapor pressure, and evaporation was found. Atmometers were used to estimate the evaporation from the surface of Yaquina Bay, and the possibility of using atmometers at sea was investigated

Field Evaluation of a Push-Pull System to Reduce Malaria Transmission

<div><p>Malaria continues to place a disease burden on millions of people throughout the tropics, especially in sub-Saharan Africa. Although efforts to control mosquito populations and reduce human-vector contact, such as long-lasting insecticidal nets and indoor residual spraying, have led to significant decreases in malaria incidence, further progress is now threatened by the widespread development of physiological and behavioural insecticide-resistance as well as changes in the composition of vector populations. A mosquito-directed push-pull system based on the simultaneous use of attractive and repellent volatiles offers a complementary tool to existing vector-control methods. In this study, the combination of a trap baited with a five-compound attractant and a strip of net-fabric impregnated with micro-encapsulated repellent and placed in the eaves of houses, was tested in a malaria-endemic village in western Kenya. Using the repellent delta-undecalactone, mosquito house entry was reduced by more than 50%, while the traps caught high numbers of outdoor flying mosquitoes. Model simulations predict that, assuming area-wide coverage, the addition of such a push-pull system to existing prevention efforts will result in up to 20-fold reductions in the entomological inoculation rate. Reductions of such magnitude are also predicted when mosquitoes exhibit a high resistance against insecticides. We conclude that a push-pull system based on non-toxic volatiles provides an important addition to existing strategies for malaria prevention.</p></div

Model simulations of a scenario in which mosquitoes are highly resistant against insecticides.

<p>Shown is the entomological inoculation rate (EIR) as a function of different levels of push efficacy. Push efficacy is expressed as the percentage of house entry reduction and pull efficacy is expressed as the relative attractiveness of the trap, compared to a human being.</p

Mean number of mosquito landings on the control and the treated fabrics.

<p>At zero, one, three and six months after treatment. Asterisks indicate a significant difference between the control and the treatment, n = 8 for all groups, error bars indicate the standard error of the mean.</p

Mean number of anopheline mosquitoes caught inside the houses.

<p>Error bars indicate standard error of the mean (SEM), n = 8 for the baseline data (n = 7 for house 3) and n = 25 for the intervention data. Asterisks indicate a significant difference-in-differences between the control and the intervention: * p < 0.05; ** p < 0.01; *** p < 0.001.</p