Seasonal and spatial heterogeneity of recent sea surface temperature trends in the Caribbean Sea and southeast Gulf of Mexico

Recent changes in ocean temperature have impacted marine ecosystem function globally. Nevertheless, the responses have depended upon the rate of change of temperature and the season when the changes occur, which are spatially variable. A rigorous statistical analysis of sea surface temperature observations over 25 years was used to examine spatial variability in overall and seasonal temperature trends within the wider Caribbean. The basin has experienced high spatial variability in rates of change of temperature. Most of the warming has been due to increases in summer rather than winter temperatures. However, warming was faster in winter in the Loop Current area and the south-eastern Caribbean, where the annual temperature ranges have contracted. Waters off Florida, Cuba and the Bahamas had a tendency towards cooling in winter, increasing the amplitude of annual temperature ranges. These detailed patterns can be used to elucidate ecological responses to climatic change in the region.     

An overview of developments and applications of oceanographic radar networks in Asia and Oceania countries

More than 110 radar stations are in operation at the present time in Asia and Oceania countries, which is nearly half of all the existing radar stations in the world, for purposes related to marine safety, oil spill response, tsunami warning, coastal zone management and understanding of ocean current dynamics, depending mainly on each country’s coastal sea characteristics. This paper introduces the oceanographic radar networks of Australia, China, Japan, Korea and Taiwan, presented at the 1st Ocean Radar Conference for Asia (ORCA) held in May 2012, Seoul, Korea, to share information about the radar network developments and operations, knowledge and experiences of data management, and research activity and application of the radar-derived data of neighbouring countries. We hope this overview paper may contribute as the first step to promotion of regional collaborations in the radar observations and data usages and applications in order to efficiently monitor the coastal and marginal sea waters along the western Pacific Ocean periphery.     

Reviews

Book reviewed in this article:
Green Politics By S. Rainbow.
Keeping New Zealand Green: Recent Environmental Reforms By P.A. Memon.
Environmental Planning in New Zealand Edited by P.A. Memon and H. C. Perkins.     

Thermal Treatment of Eight CVOC Source Zones to Near Nondetect Concentrations

In situ thermal desorption (ISTD) was used for the treatment of eight separate source zones containing chlorinated solvents in a tight loess (silt/clay) above the water table. The source areas were as much as 365 m (1200 feet) apart. A target volume of 38,200 m³ (49,950 cubic yards) of subsurface material to a depth of 9.1 m (30 feet) was treated in a period of 177 days. Energy was delivered through 367 thermal conduction heater borings, and vapors were extracted from 68 vertical vacuum wells. A vapor extraction and capture system, including a surface cover and vertical vacuum wells next to heater borings, provided for effective pneumatic control and capture of the chlorinated volatile organic compound (CVOC) vapors. A central treatment system, based on condensation and granular activated carbon filtration, was used to treat the vapors. Approximately 5675 kg (12,500 pounds) of contaminants was recovered in the extracted vapors. Forty-seven soil samples were used to document remedial performance. Based on these, the concentrations of the target contaminants were reduced to below the target remedial goals in all eight areas, typically with concentrations below 0.01 mg/kg in locations that had had CVOC concentrations higher than 1000 mg/kg. Turn-key costs for the thermal remediation were $3.9 million, and the unit treatment cost, including all utilities, was $103 per cubic meter treated ($79 per cubic yard).     

A Method of Swell-Wave Parameter Extraction From HF Ocean Surface Radar Spectra

A new method for the extraction of swell-wave parameters from high-frequency (HF) radar spectra is presented. The method of extraction of the parameters, period, direction, and height, relies on a frequency-modulation approach that describes the hydrodynamic interaction of the swell waves with the resonant, shorter, Bragg waves. The analysis process minimizes the electromagnetic second-order interaction and a simulation model was used to validate the approach. This simplified method provides a fast means of examining swell conditions over large areas of the ocean surface. Data are acquired using a pair of coastal ocean surface radar (COSRAD) systems deployed at Tweed Heads, Qld., Australia. The radar covers a sweep (approximately 60deg) every 30 min with spatial resolution of the order of 3 km. A sample set of data from this deployment is used in a case study to show the extraction of swell direction and amplitude using these methods. The results support the use of the COSRAD HF radar for mapping swell in the near-shore zone     

Wave-induced Benthic Velocity Variations in Shallow Waters

Waves propagating from deep water into shallow coastal areas produce oscillatory currents near the sea bottom. The magnitude of these currents depend upon the period and amplitude of the incoming waves, and the dissipation mechanism such as wave breaking and bottom friction. Field experiments in a gently shoaling bay, i.e. Cleveland Bay, Northern Australia, showed that there is a broad band of water at around 6 m depth, where the benthic surge velocities are maximum. Both further inshore and offshore, the bottom velocities were less than at 6 m depth, contrary to the normal expectation that the velocities should increase as the water becomes shallower. A new and computationally efficient wave model was developed and was able to reproduce experimental results for waves above 50 cm wave height, but not for small waves (wave height about 30 cm). One implication of this higher band of benthic surge velocities may be to produce high water turbidities in this region. Turbidity data from Cleveland Bay is consistent with this hypothesis.