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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Upwelling at the ice edge - A mechanism for deep water formation?

This study sets forward a hypothesis which anticipates deep water formation due to ice edge upwelling. The upwelling can raise thermocline waters (the lower Arctic Intermediate Water) to the surface or near it, where the water is exposed to cooling, evaporation, mixing, and oxygenation. Thus, upwelling can act as a preconditioning mechanism for deep convection. The conjecture would also explain the salinity range of the Greenland Sea Deep Water if the upper and lower Arctic Intermediate Water masses are mixed so that the latter has at least an 80-percent contribution. It is also anticipated that the convection events induced by ice edge upwelling during winter season could give rise to a new deep water annual production rate consistent with observations.

Hakkinen, Sirpa↗
NASA NTRS1995

North Atlantic Deep Water and the World Ocean

North Atlantic Deep Water (NADW) by being warmer and more saline than the average abyssal water parcel introduces heat and salt into the abyssal ocean. The source of these properties is upper layer or thermocline water considered to occupy the ocean less dense than sigma-theta of 27.6. That NADW convects even though it's warmer than the abyssal ocean is obviously due to the high salinity. In this way, NADW formation may be viewed as saline convection. The counter force removing heat and salinity (or introducing fresh water) is usually considered to to take place in the Southern Ocean where upwelling deep water is converted to cold fresher Antarctic water masses. The Southern ocean convective process is driven by low temperatures and hence may be considered as thermal convection. A significant fresh water source may also occur in the North Pacific where the northward flowing of abyssal water from the Southern circumpolar belt is saltier and denser than the southward flowing, return abyssal water. The source of the low salinity input may be vertical mixing of the low salinity surface water or the low salinity intermediate water.

Arnold L Gordon↗
NASA NTRS1984

Quaternary North Atlantic Surface Paleoceanography in Regions of Potential Deep-water Formation

At the time scale of the Quaternary climate cycles, the sites of formation of North Atlantic Deep Water are not known. The interglacial extreme is presumably exemplified by the modern regions; the Norwegian, Greenland and Labrador Seas. During the major glacial-age coolings in the North Atlantic, the sites may have shifted well to the south, perhaps as far as the limit of the polar front at 40 to 50 N. Still other sites may have been important during intermediate climatic conditions. Because of the close coupling of high-latitude surface waters to North Atlantic Deep Water in the modern ocean, the history of sea-surface temperature (SST) oscillations across the high-latitude North Atlantic is relevant to an understanding of deep-water formation on the longer time scales.

Ruddiman, W. F.↗
NASA NTRS2019

Water-Saving Agriculture Can Deliver Deep Water Cuts for China

China is working hard to reconcile growing demands for freshwater with already oversubscribed renewable water resources. However, the knowledge essential for setting and achieving the intended water consumption cuts remains limited. Here we show that on-farm water management interventions such as improved irrigation and soil management practices for maize cultivation can lead to substantial water consumption reductions, by a simulated total of 28-46% (7-14 billion m3/year) nationally, with or without the impacts of climate change. The water consumption cut is equivalent to 16-31% of the ultimate capacity of the South-North Water Transfer Project. Much of the reduction is achievable at the populous and water-stressed North China Plain and Northeast China. Meanwhile, the interventions can increase maize production by an estimated 7-15%, meeting 22-28% of demand increase projected for 2050. The water management and food production improvements obtained are crucial for achieving multiple Sustainable Development Goals (SDGs) related to water, land, and food in China and far beyond.

Guorui Huang↗
NASA NTRS2001

A Multi-Band Analytical Algorithm for Deriving Absorption and Backscattering Coefficients from Remote-Sensing Reflectance of Optically Deep Waters

A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.

Lee, Zhong-Ping↗
NASA NTRS1974

A system of automated processing of deep water hydrological information

An automated system for primary and scientific analysis of deep water hydrological information is presented. Primary processing of the data in this system is carried out on a drifting station, which also calculates the parameters of vertical stability of the sea layers, as well as their depths and altitudes. Methods of processing the raw data are described.

Romantsov, V. A.↗
NASA NTRS1989

Contributions of the Siberian shelf polynyas to the Arctic Ocean intermediate and deep water

To investigate the role of Siberian Shelf polynyas in water mass formation, and that of Whalers Bay in the cooling of the West Spitsbergen Current, satellite observations from the Nimbus 7 scanning multichannel microwave radiometer are used to determine the size and location of polynyas for November-March, 1978-1982. If salt contributes only to the Arctic Intermediate Water, the results show that the continental shelves can produce 20-60 percent of this water. Alternatively, if the salt contributes only to the deep water of the Eurasian Basin, then without consideration of the mixing of the bottom water with the Greenland and Norwegian Sea water, the contribution from the shelves yields a renewal time of about 100 years. These results imply that there is insufficient water produced in the shelf polynyas to perform all of the roles that have historically been assigned to it.

Martin, Seelye↗
NASA NTRS1984

Climatic Impact of a Change in North Atlantic Deep Water Formation

The response of the ocean to climate changes is one of the most uncertain questions regarding the impact of increasing CO2 on climate and society. North Atlantic deep water (NADW) formation apparently depends on a complex confluence of different water masses originating in different areas, all of which will presumably be affected by changes in wind, evaporation, etc., as the atmosphere warms. To analyze from first principles what the effect will be on NADW formation is a task which requires an ocean modeling capability not yet available. As a substitute, past climates can be investigated to see if there is any evidence for alterations in NADW formation. In addition, the possible impact of such changes on climate can be explored. An estimate of NADW sensitivity (at least in the past) and of the climate consequences can be studied. The North Atlantic surface water temperatures can be reconstructed to indicate a substantial cooling between 11,000 and 10,000 years B.P. Were NADW formation to have ceased, it would have resulted in cooler surface waters; whether the reconstructed temperatures were due to this or some other effect cannot be determined at this time. Nevertheless, it was decided that it would be useful to see what the effect these colder temperatures would have had on the climate.

Rind, D.↗
NASA NTRS1984

Deep Water Formation

Some simple arguments on plumes of dense water and filling boxes were given. What determines the time for a large-scale environment to be modified by the injection of dense water at its edge is the mass flux, not the buoyancy flux. However, it is the denser buoyancy flux, when there are several competing plumes (e.g., the Mediterranean outflow versus the Denmark Strait outflow) that determines which plume will provide the bottom water for that ocean basin. It was noted that the obvious laboratory experiment (rotate a pie-shaped annulus, and heat/cool it on the surface) had never been performed. Thus, to some extent our belief that deep convection is somehow automatic at high latitudes to close off some ill-defined meridional circulation has never been tested. A summary of deep convection was given. The two fundamental formation mechanisms were shown. Of the two, it is open-ocean convection which forms the water which supplies the Denmark Strait overflow -- in all likelihood, as formation in the Greenland Sea remains stubbornly unobserved. But it is the slope convection which finally creates North Atlantic deep water, following the Denmark Strait overspill.

Killworth, P. D.↗
NASA NTRS1995

Simulated interannual variability of the Greenland Sea deep water formation and its connection to surface forcing

A fully prognostic Arctic ice-ocean model is used to study the interannual variability of deepwater formation in the Greenland Sea Gyre based on the simulations for the Arctic ice-ocean system for the period 1955 and 1960 - 1985. The model uses monthly climatology for thermodynamic forcing components (such as air temperature and cloudiness), together with constant annual net precipitation and river runoff. The daily wind forcing is derived from analyzed sea level air pressures from the National Center for Atmospheric Research (NCAR). In summary, the model shows that the occurence of deep convection in the Greenland Sea Gyre is controlled by the extensive Fram Strait ice export and/or local wind conditions in the Greenland Sea. In the latter case the weakening of the local wind curl allows the Polar Front to move eastward. The movement of the Polar Front causes adverse ice conditions, often together with much larger than normal ice export from the Arctic, such as in 1968, which can block convection in the gyre. The density difference between upper and lower layers is investigated as an indication of water mass formation through convection, occurring as strong diffusion in the model. The model-simulated density difference between the average top 100 m and deep levels reveals that the period 1960 - 1985 had only a few distinct years with weak stratification, and, especially, the model predicts no deep convection since the nid-1970s. The common factor for the years of the weakest decrease of the model-predicted heat content of the upper 2000 m which can, to a high degree, be explained by local heat loss.

Haekkinen, Sirpa↗
NASA NTRS1995

North Atlantic Deep Water Formation

Various studies concerning differing aspects of the North Atlantic are presented. The three major topics under which the works are classified include: (1) oceanography; (2) paleoclimate; and (3) ocean, ice and climate modeling.

T Bennett↗
NASA NTRS1984

North Atlantic Deep Water Formation: Information from Ice Cores

The main results of measurements of the CO2 concentration of air occluded in natural ice during periods of climatic change are presented, as well as other measured ice core parameters. Elements of an interpretation of the data in terms of mechanisms of changing environmental systems are briefly discussed.

Oeschger, H.↗
NASA NTRS2001

Remote-Sensing Reflectance and Inherent Optical Properties for Optically Deep Waters: A Revisit

Remote-sensing reflectance (r(rs)) is defined as the ratio of upwelling radiance to downwelling irradiance. Relationships between remote-sensing reflectance and inherent optical properties serve as the basis for ocean-color modeling, as well as for spectral deduction of oceanic constituents through analytical/semi-analytical models of ocean color. A decade ago, a simple and concise formula based on Monte Carlo simulations was developed by relating rrs to a property u, the ratio of backscattering (b(b)) to the sum of absorption (a) and backscattering (u = b(b)/(a+b(b))). This relationship generally ignored the shape differences in phase functions between molecular scattering and particle scattering. In this study, the relationship is updated with separate parameters for molecular and particle scattering, based on the Radiative Transfer Equation through use of Hydrolight numerical solutions. The new approach fits r(rs) better than an earlier traditional formula, for both clear and turbid waters.

Lee, Zhong-Ping↗
NASA NTRS1992

Tektite-bearing, deep-water clastic unit at the Cretaceous-Tertiary boundary in northeastern Mexico

The hypothesis of Cretaceous-Tertiary (K-T) boundary impact on Yucatan, Mexico, predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves. An outcrop along the Arroyo el Mimbral in northeastern Mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic-marl sequence deposited at more than 400 m water depth. The marls were found to be unsuitable for determining magnetostratigraphy, but foraminiferal biostratigraphy places the clastic unit precisely at the K-T boundary. We interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact. The clastic unit comprises three main subunits. (1) The basal "spherule bed" contains glass in the form of tektites and microtektites, glass spherules replaced by chlorite-smectite and calcite, and quartz grains showing probable shock features. This bed is interpreted as a channelized deposit of proximal ejecta. (2) A set of lenticular, massive, graded "laminated beds" contains intraclasts and abundant plant debris, and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water. (3) At the top, several thin "ripple beds" composed of fine sand are separated by clay drapes; they are interpreted as deposits of oscillating currents, perhaps a seiche. An iridium anomaly (921 +/- 23 pg/g) is observed at the top of the ripple beds. Our observations at the Mimbral locality support the hypothesis of a K-T impact on nearby Yucatan.

NASA Discipline Number 52-40↗
NASA NTRS2006

Implications of Cometary Water: Deep Impact, Stardust and Hayabusa

Three recent in situ spacecraft missions have explored comets or asteroids, producing data in conflict with the standard comet paradigm, the Whipple Dirty Snowball Model (DSM). We have developed an alternative Wet Comet Model (WCM) which proposes that comets undergo an irreversible phase change to a wet comet when they enter within Mars orbit. The WCM may explain some of the observational discrepancies seen by Deep Impact, Stardust and Hayabusa. In particular, it accurately predicted Deep Impact observation of organics, biominerals, and meltwater temperatures. Predictions concerning Stardust s returned cometary dust particles have yet to be falsified, but if comets are largely composed of the silicates seen by Stardust, there may be a cometary explanation for Itokawa s low density rubble-pile observed by Hayabusa.

Sheldon, Robert B.↗
NASA NTRS1992

Operational strategies for contamination control of composite materials

Composite materials, used on many instruments, are a potential contamination source for sensitive sensors, especially for sensors or detectors cooled below -80 C. It is a well known fact that composite materials absorb water during fabrication, integration, test, and launch activities and desorb this water under vacuum conditions. Water absorption can be divided into two types: shallow water and deep water. Shallow water is generally about 500 A thick on a clean material surface and is easily desorbed under vacuum conditions. Deep water is a function of the material and is absorbed into the bulk of the material. Deep water can outgas for weeks, months, or years, depending on the vent path, the amount of absorbed water, and the temperature of the material. Several operational strategies have been successfully employed on the Wide Field Planetary Camera. The operational strategies include ultradry gaseous nitrogen purge, dew point of less than -80 C, and vacuum bake-out with verification of outgassing rates. The nitrogen purge is instituted during the fabrication phase and is continued through launch activities. Great care is taken to avoid extended periods of time that the material is exposed to the ambient environment (50 percent relative humidity). On-orbit operational strategies include heat-up and cool-down scenarios which allow the deep water to be sufficiently outgassed before cooling the sensors or detectors.

Hansen, Patricia A.↗