Locating the orbits delineated by tidal streams

We describe a technique that finds orbits through the Galaxy that are consistent with measurements of a tidal stream, taking into account the extent that tidal streams do not precisely delineate orbits. We show that if accurate line-of-sight velocities are measured along a well defined stream, the technique recovers the underlying orbit through the Galaxy and predicts the distances and proper motions along the stream to high precision. As the error bars on the location and velocities of the stream grow, the technique is able to find more and more orbits that are consistent with the data and the uncertainties in the predicted distances and proper motions increase. With radial-velocity data along a stream ~40deg long and <0.3deg wide on the sky accurate to ~1 km/s the precisions of the distances and tangential velocities along the stream are 4 percent and 5 km/s, respectively. The technique can be used to diagnose the Galactic potential: if circular-speed curve is actually flat, both a Keplerian potential and Phi(r) proportional to r are readily excluded. Given the correct radial density profile for the dark halo, the halo's mass can be determined to a precision of 5 percent.Comment: 13 pages, 16 figures, submitted to MNRA

U.S. Extended Continental Shelf Cruise to Map Gaps in Kela and Karin Ridges, Johnston Atoll, Equatorial Pacific Ocean

The objectives for cruise KM14-17 are to map the bathymetry of two gaps in two submarine ridges in the vicinity of Johnston Atoll. One ridge gap occurs along the informally named Keli Ridge (Hein et al., 2005) south of Johnston Atoll and the other ridge gap occurs north of Johnston Atoll that separates Sculpin Ridge (also informally called Karin Ridge) and Horizon Ridge, all in the central equatorial Pacific (Fig. 1). The cruise took advantage of a scheduled dead-head transit from Papeete, Tahiti to Honolulu, Hawai’i that could be extended for 5 days to include the planned mapping. The mapping is in support of the U.S. (Extended Continental Shelf (ECS) Task Force. These areas were identified by the ECS Central Pacific Integrated Regional Team as having the potential for an ECS

Analysis of non-premixed turbulent reacting flows

Studies of chemical reactions occurring in turbulent flows are important in the understanding of combustion and other applications. Current numerical methods are limited in their applications due to the numerical resolution required to completely capture all length scales, but, despite the fact that realistic combustion cannot be solved completely, numerical simulations can be used to give insight into the interaction between the processes of turbulence and chemical reaction. The objective was to investigate the effects of turbulent motion on the effects of chemical reaction to gain some insight on the interaction of turbulence, molecular diffusion, and chemical reaction to support modeling efforts. A direct turbulence simulation spectral code was modified to include the effects of chemical reaction and applied to an initial value problem of chemical reaction between non-premixed species. The influence of hydrodynamics on the instantaneous structure of the reaction was investigated. The local scalar dissipation rates and the local reaction rates were examined to determine the influence of vorticity or rate of strain on the reaction and the structure of the scalar field

From the Arctic to the Tropics: The U.S. UNCLOS Bathymetric Mapping Program

Since CHC2006, the University of New Hampshire’s Center for Coastal & Ocean Mapping/Joint Hydrographic Center has mapped with multibeam, the bathymetry of an additional ~220,000 km2 of seafloor in areas as diverse as the Arctic, the Northern Marianas of the western Pacific and the Gulf of Mexico. The mapping supports any potential U.S. submission for of extended continental shelves under Article 76 of the United Nations Convention of the Law of the Sea. Consequently, the mapping has concentrated on capturing the complete extent of the 2500-m isobath and the zone where the Article 76-defined foot of the slope exists. In practice, the complete area between ~1500 and ~4500 m water depths is mapped in each region (with the exception of the Arctic Ocean). The data have been collected in conditions that range from harsh Arctic sea ice to the calms of the Philippine Sea tropics. Although, some of the conditions have limited the quality of some of the data, the data quality is generally quite good and geological surprises have been uncovered on each of the cruises

Mapping in the Arctic Ocean in Support of a Potential Extended Continental Shelf

Under Article 76 of The United Nations Convention on the Law of the Sea (UNCLOS; U.N. 1997), coastal states may, under certain circumstances, gain sovereign rights over the resources of the seafloor and subsurface of “submerged extensions of their continental margin” beyond the recognized 200 nautical mile (nmi) limit of their Exclusive Economic Zone (EEZ). The establishment of an “extended continental shelf” (ECS) under Article 76 involves the demonstration that the area of the ECS is a “natural prolongation” of a coastal state’s territorial landmass and then the application of a series of formulae and limit lines that are based on determination of the “foot of the slope,” (defined in Article 76 as the maximum change in gradient at it’s base), the underlying sediment thickness, and the locations of the 2500 m isobath and the 350 nmi line from the territorial sea base line. Although the United States has not yet acceded to the UNCLOS, increasing recognition that implementation of Article 76 could confer sovereign rights over large and potentially resource-rich areas of the seabed beyond its current 200 nautical mile (nmi) limit has renewed interest in the potential for accession to the treaty and spurred U.S. efforts to map area of potential “extended continental shelf”

High Resolution Mapping in support of UNCLOS Article 76: Seeing the seafloor with new eyes

Since 2003, the Center for Coastal & Ocean Mapping/Joint Hydrographic Center at the University of New Hampshire (UNH) has been conducting multibeam mapping of many U.S. continental margins in areas where there is a potential for an extended continental shelf as defined under Article 76 of the United Nations Convention on the Law of the Sea. UNH was directed by Congress, through funding by the National Oceanic & Atmospheric Administration, to map the bathymetry in areas in the Arctic Ocean, Bering Sea, Gulf of Alaska, Northwest Atlantic, northern Gulf of Mexico, the Northern Mariana Islands, Kingman Reef and Palmyra Atoll (Fig. 1). The purpose of these surveys is to accurately locate the 2500-m isobath and to collect the bathymetry data required to eventually determine the location of the maximum change in gradient on Figure 1. Locations and year of bathymetry mapping (yellow areas) for U.S. UNCLOS concerns. the continental rises. A total area of about 862,000 km2 has been completed; approximately 250,000 km2 remains to be mapped. The area between the ~1000 and ~4800-m isobaths has been mapped on each of the completed margins. The mapping has been conducted with multibeam echosounders (MBES) that typically collect soundings with a spacing of ~50 m or less in the focused water depths. After each area is mapped, the data are gridded at 100-m spatial resolution although higher resolution is possible in the shallower regions. The depth precision achieved on all of the cruises has been \u3c1% of the water depth and typically has been \u3c0.5% of the water depth, based on cross-line comparisons. Navigation on all of the cruises has been acquired with inertial-aided DGPS using commercial differential corrections that provide 2 position accuracies much better than ±5 m. All of the MBES systems used produce acoustic backscatter as well as bathymetry but the backscatter quality varies among systems and conditions. Table 1 is a summary of the mapping completed and of areas yet to be mapped for bathymetry. The data are all processed at sea by UNH personnel during their collection and the data, grids and views of the processed data are posted on the worldwide web soon after completion of each area. The data, grids and images can be viewed and downloaded at http://ccom.unh.edu/law_of_the_sea.html