Currents, Fronts and Fine Structure in the Marginal Ice Zone of the Chukchi Sea

The article of record as published may be found at https://doi.org/10.1017/S0032247400021975Project MIZPAC (Marginal Ice Zone Pacific) was initiated in 1971 by the Arctic Submarine Laboratory, San Diego, California, to further the US Navy's understanding of problems associated with operating submarines under ice-covered oceans. Oceanographers from the Naval Postgraduate School took part in six summer cruises to the marginal sea ice zone (MIZ) of the shallow Chukchi Sea between 1971 and 1978 (Fig 1), providing the first detailed observations of the temperature-salinity structure within this dynamically active zone. Strong horizontal gradients of temperature and salinity marking boundaries between water masses (fronts), are widespread and well developed (Paquette and Bourke 1981). Where water masses intrude upon each other large-scale temperature inversions (anomalous increases in temperature with depth) often appear. Termed fine structure, these temperature anomalies include some of the largest observed anywhere in the world's oceans, sometimes exceeding 2°C over vertical distances of 5–10 m (Paquette and Bourke 1979). This article describes some of the fronts and fine structures observed in the Chukchi Sea, and shows how they develop within the general patterns of sea ice and circulation

Development of an Arctic Low Frequency Ambient Noise Model

LONG TERM GOALS: To develop a low frequency Arctic ambient noise model to predict extreme (loud /quiet) noise events due the presence or absence of storms.Award No. N0001497WR3009

Atlantic water on the Chukchi Shelf

An anomalously warm saline layer in the bottom of the shallow Chukchi Sea in August 1975 is believed due to a surge which drove water from the Atlantic Layer of the Arctic Ocean up onto the shelf. Two earlier occurrences of this kind of water in the Chukchi Sea have been identified in historical data.Submitted to: Director, Arctic Submarine Laboratory Naval Undersea Center, San Diego, CA.http://archive.org/details/atlanticwateronc00bourProject Order No. 00010N

Processing time not modality dominates shift costs in the modality-shifting effect

Shifting attention between visual and auditory targets is associated with reaction time costs, known as the modality-shifting effect. The type of modality shifted from, e.g., auditory or visual is suggested to have an effect on the degree of cost. Studies report greater costs shifting from visual stimuli, yet notably used visual stimuli that are also identified slower than the auditory. It is not clear whether the cost is specific to modality effects, or with identification speed independent of modality. Here, to interpret whether the effects are due to modality or identification time, switch costs are instead compared with auditory stimuli that are identified slower than the visual (inverse of tested previously). A second condition used the same auditory stimuli at a low intensity, allowing comparison of semantically identical stimuli that are even slower to process. The current findings contradicted suggestions of a general difficulty in shifting from visual stimuli (as previously reported), and instead suggest that cost is reduced when targets are preceded by a more rapidly processed stimulus. ‘Modality-Shifting’ as it is often termed induces shifting costs, but the costs are not because of a change of modality per se, but because of a change in identification speed, where the degree of cost is dependent on the processing time of the surrounding stimuli

Observations on the coastal current of Arctic Alaska

This paper describes characteristics of the warm coastal current in the vicinity of the ice margin in the Chukchi and Beaufort seas. The warm current originates in Bering Strait and is traced around Pt. Barrow to longitude 152°W in the Beaufort Sea. In the Chukchi Sea it is concentrated near the surface, overlying dense relict bottom water trapped by the shallow depths. Eastward, as the bottom deepens, the warm water descends to mid-depth, eventually becoming warmest near bottom in depths of 30 to 50 m. Mechanisms for cooling and dilution of the warm water are discussed

The Earliest Phases of Star formation (EPoS): Temperature, density, and kinematic structure of the star-forming core CB 17

Context: The initial conditions for the gravitational collapse of molecular cloud cores and the subsequent birth of stars are still not well constrained. The characteristic cold temperatures (about 10 K) in such regions require observations at sub-millimetre and longer wavelengths. The Herschel Space Observatory and complementary ground-based observations presented in this paper have the unprecedented potential to reveal the structure and kinematics of a prototypical core region at the onset of stellar birth. Aims: This paper aims to determine the density, temperature, and velocity structure of the star-forming Bok globule CB 17. This isolated region is known to host (at least) two sources at different evolutionary stages: a dense core, SMM1, and a Class I protostar, IRS. Methods: We modeled the cold dust emission maps from 100 micron to 1.2 mm with both a modified blackbody technique to determine the optical depth-weighted line-of-sight temperature and column density and a ray-tracing technique to determine the core temperature and volume density structure. Furthermore, we analysed the kinematics of CB17 using the high-density gas tracer N2H+. Results: From the ray-tracing analysis, we find a temperature in the centre of SMM1 of 10.6 K, a flat density profile with radius 9500 au, and a central volume density of n(H) = 2.3x10^5 cm-3. The velocity structure of the N2H+ observations reveal global rotation with a velocity gradient of 4.3 km/s/pc. Superposed on this rotation signature we find a more complex velocity field, which may be indicative of differential motions within the dense core. Conclusions: SMM is a core in an early evolutionary stage at the verge of being bound, but the question of whether it is a starless or a protostellar core remains unanswered.Comment: published in A&

USNS BARTLETT Cruise to the Greenland Sea in September 1989: Data Report

As a component of the Greenland Sea Project, a hydrographic cruise was conducted on board the USNS BARTLETT during September 1989 in the southern Greenland Sea to characterize the water mass structure and circulation features of the Jan Mayen Current (JMC). A total of 48 high-quality CTD stations were occupied to depths of 1000 m; five stations extended to 3000 m or more. Five north-south tending transects permitted tracking of the JMC by its low temperature (< 0°C) , low salinity near-surface core. The JMC could also be well defined from its warm, saline intermediate water properties. Deep stations made in the trough of the Jan Mayen Fracture Zone suggest that the interchange of deep and bottom water from the Greenland and Norwegian Seas via this trough is a slow diffusive process and not an active advective feature as previously thought.Arctic Submarine Laboratory, Naval Ocean Systems Center, San Diego, CA.http://archive.org/details/usnsbartlettcrui00bourO&MN, Direct Fundin