217 research outputs found
Measurements and models of fine-structure, internal gravity waves and wave breaking in the deep ocean
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September, 1976Measurements of horizontal and vertical current by propeller cluster
current meters and temperature by thermistors mounted on a rigid array
8 m high and 20 m long moored in the oceanic main thermocline near
Bermuda are interpreted in terms of thermocline-trapped internal wave
modes in the presence of temperature and density fine-structure.
Two turning-point uniformly valid asymptotic solutions to the internal
wave equation are developed to describe the wave functions. Mode
decay beyond the turning point in depth or frequency produces a sharp
cutoff in vertical current spectra above the local buoyancy frequency
N(z). An internal wave wavenumber-frequency spectral model Î(α,Ï) =
E(Ï/No)-2 (α./α0)-2 describes vertical current spectra and potential energy
to horizontal kinetic energy ratios. The red wavenumer shape suppresses
peaks in both these quantities at frequencies near N(z). The data are
consistent with time-averaged horizontal isotropy of the wave field. A
dip in the vertical current spectra at 0.5 cph not predicted by the model
appears related to the bottom slope.
Temperature fine-structure is modeled as a passive vertical field
advected by internal waves. Quasi-permanent fine-scale features of the
stratification and vertically small-scale internal waves are indistinguishable
in this study. The model of McKean (1974) is generalized to
include fine-structure fields specified by their vertical wavenumber
spectra as well as different Poisson-distributed layer models. Together
with the trapped internal wave model, moored temperature spectra, temperature
vertical difference spectra, and coherence over vertical separations
are described using a fine-structure vertical wavenumber spectrum
PT(k) =ATk-5/2 which agrees with other spectra made using vertical profiling
instruments in the range 0.1 to 1.0 cpm.
Horizontal current fine-structure is also modeled as a passive field
advected vertically by long internal waves. The model describes moored
horizontal current spectra (least successfully at frequencies near N(z))
and finite-difference vertical shear spectra.
Contours of temperature in depth versus time indicate possible mixing
events. These events appear concurrently with high shear and
Richardson numbers O. 25†R †1.0. Over 7 m a cutoff in Ri at 0.25 is
observed, indicating saturation of the internal wave spectrum. Spectra
of finite-difference approximations to shear and buoyancy frequency are
dominated by fine-structure contributions over nearly the whole internal
wave range, suggesting that breaking is enhanced by fine-structure.
Breaking appears equally likely at all frequencies in the internal wave
range.This research was supported by Office of Naval Research contract N00014-67-0204-0047 and continuation contract NOOOl4-75-C-0291
Geostrophic equatorial deep jets
Deep zonal jets in the western Pacific are geostrophic in character at latitudes of a fraction of a degree. This evidence corroborates the interpretation that deep jets very close to the equator take the form of Kelvin waves. Vertical displacements inferred from GEOSECS density profiles in the Pacific and Atlantic suggest deep jets are a general feature of equatorial oceans
Observations of seasonal subduction at the Iceland-Faroe Front
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 4026â4040, doi:10.1002/2015JC011501.The polar front in the North Atlantic is bound to the ridge between Iceland and the Faroe Islands, where about one-half of the northward transport of warm Atlantic Water into the Nordic Seas occurs, as well as about one sixth of the equatorward dense overflow. We find a low salinity water mass at the surface of the Iceland-Faroe Front (IFF), which in wintertime subducts along outcropping isopycnals and is found in much modified form on the Atlantic side of the Iceland-Faroe Ridge (IFR) crest. The features found on the Atlantic side of the crest at depth have temperature and salinity characteristics which are clearly traceable to the surface outcrop of the IFF. The presence of coherent low salinity layers on the Atlantic side of the IFR crest has not been previously reported. Warm waters above the IFR primarily feed the Faroe Current, and injection of a low salinity water mass may play an early role in the water mass transformation taking place in the Nordic Seas. The seasonality of the intrusive features suggests a link between winter convection, mixed layer instability and deep frontal subduction. These low salinity anomalies (as well as a low oxygen water mass from the Iceland Basin) can be used as tracers of the intermediate circulation over the IFR.National Science Foundation OCE Division . Grant Numbers: OCE-1029344 , OCE-05505842016-12-1
Salinity and temperature balances at the SPURS central mooring during fall and winter
Author Posting. © The Oceanography Society, 2015. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 28, no. 1 (2015): 56-65, doi:10.5670/oceanog.2015.06.One part of the Salinity Processes in the Upper-ocean Regional Study (SPURS) field campaign focused on understanding the physical processes affecting the evolution of upper-ocean salinity in the region of climatological maximum sea surface salinity in the subtropical North Atlantic (SPURS-1). An upper-ocean salinity budget provides a useful framework for increasing this understanding. The SPURS-1 program included a central heavily instrumented mooring for making accurate measurements of air-sea surface fluxes, as well as other moorings, Argo floats, and gliders that together formed a dense observational array. Data from this array are used to estimate terms in the upper-ocean salinity and heat budgets during the SPURS-1 campaign, with a focus on the first several months (October 2012 to February 2013) when the surface mixed layer was becoming deeper, fresher, and cooler. Specifically, we examine the salinity and temperature balances for an upper-ocean mixed layer, defined as the layer where the density is within 0.4 kg mâ3 of its surface value. The gross features of the evolution of upper-ocean salinity and temperature during this fall/winter season are explained by a combination of evaporation and precipitation at the sea surface, horizontal transport of heat and salt by mixed-layer currents, and vertical entrainment of fresher, cooler fluid into the layer as it deepened. While all of these processes were important in the observed seasonal (fall) freshening at this location in the salinity-maximum region, the variability of salinity on monthly-to-intraseasonal time scales resulted primarily from horizontal advection.J.T. Farrar,
A.J. Plueddemann, J.B. Edson, and the deployment of
the central mooring were supported by NASA grant
NNX11AE84G. L. Rainville, C. Lee, C. Eriksen, and the
Seaglider program were supported by NASA grant
NNX11AE78G. R. Schmitt was supported by NSF grant
OCE-1129646. B. Hodges and D. Fratantoni were supported
by NASA grant NNX11AE82G. The Prawler
moorings were funded by PMEL. The data analysis
was also supported by NASA grant NNX14AH38G
Autonomous multi-platform observations during the Salinity Processes in the Upper-ocean Regional Study
Author Posting. © The Oceanography Society, 2017. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 30, no. 2 (2017): 38â48, doi:10.5670/oceanog.2017.218.The Salinity Processes in the Upper-ocean Regional Study (SPURS) aims to understand the patterns and variability of sea surface salinity. In order to capture the wide range of spatial and temporal scales associated with processes controlling salinity in the upper ocean, research vessels delivered autonomous instruments to remote sites, one in the North Atlantic and one in the Eastern Pacific. Instruments sampled for one complete annual cycle at each of these two sites, which are subject to contrasting atmospheric forcing. The SPURS field programs coordinated sampling from many different platforms, using a mix of Lagrangian and Eulerian approaches. This article discusses the motivations, implementation, and first results of the SPURS-1 and SPURS-2 programs.SPURS is supported by multiple NASA grants, with
important additional contributions from the US
National Science Foundation, NOAA, and the Office
of Naval Research, as well as international agencies. SVP drifters are deployed with support
from NASA and the NOAA funded Global Drifter
Program at the Lagrangian Drifter Laboratory of
the Scripps Institution of Oceanography. SVP-S2
drifters are provided by NOAA-AOML and NASA.
PRAWLER mooring development is supported
by NOAAâs Office of Oceanic and Atmospheric
Research, Ocean Observing and Monitoring Division,
and by NOAA/PMEL
Relationship between C-telopeptide pyridinoline cross-links (ICTP) and putative periodontal pathogens in periodontitis
Crevicular fluid pyridinoline cross-linked carboxyterminal telopeptide of type 1 collagen (ICTP) is predictive for future alveolar bone loss in experimental periodontitis in dogs. The present study sought to relate ICTP to a panel of subgingival species in subjects exhibiting various clinical presentations such as health ( n = 7), gingivitis ( n = 8) and periodontitis (n=21), 28 subgingival plaque and GCF samples were taken from mesiobuccal sites m each of 36 subjects. The presence and levels of 40 subgtngivai taxa were determined in plaque samples using whole genomic DNA probes and checkerboard DNA-DNA hybridization. GCF ICTP levels were quantified using radioimmunoassay (RIA). Clinical assessments made at the same sites included: BOP, gingival redness, plaque, pocket depth, and attachment level. Differences among ICTP levels in the 3 subject groups were sought using the Kruskal-Wallis test. Relationships between ICTP levels and clinical parameters as well as subgingival species were determined by regression analysis. The results demonstrated significant differences among disease categories for GCF ICTP levels for healthy (1.1+0.6 pg/site (mean±SEM)) gingivitis (14.8±6.6 pg/site) and penodontitts subjects (30.3 + 5.7 pg/site) ( p = 0.0017). ICTP levels related modestly to several clinical parameters. Regression analysis indicated that ICTP levels correlated strongly with mean subject levels of several periodontal pathogens including B. forsythus, P. gingivitis, P. intermedia, P. nigrescens and T. dentcola ( p < 0.01). The data indicate that there is a positive relationship between the putative bone resorptive marker ICTP and periodontal pathogens.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74809/1/j.1600-051X.1998.tb02383.x.pd
COMAP Early Science: VIII. A Joint Stacking Analysis with eBOSS Quasars
We present a new upper limit on the cosmic molecular gas density at
obtained using the first year of observations from the CO Mapping
Array Project (COMAP). COMAP data cubes are stacked on the 3D positions of 282
quasars selected from the Extended Baryon Oscillation Spectroscopic Survey
(eBOSS) catalog, yielding a 95% upper limit for flux from CO(1-0) line emission
of 0.210 Jy km/s. Depending on the assumptions made, this value can be
interpreted as either an average CO line luminosity of eBOSS
quasars of K km pc s, or an average
molecular gas density in regions of the universe containing
a quasar of M cMpc. The
upper limit falls among CO line luminosities obtained from
individually-targeted quasars in the COMAP redshift range, and the
value is comparable to upper limits obtained from other
Line Intensity Mapping (LIM) surveys and their joint analyses. Further, we
forecast the values obtainable with the COMAP/eBOSS stack after the full 5-year
COMAP Pathfinder survey. We predict that a detection is probable with this
method, depending on the CO properties of the quasar sample. Based on these
achieved sensitivities, we believe that this technique of stacking LIM data on
the positions of traditional galaxy or quasar catalogs is extremely promising,
both as a technique for investigating large galaxy catalogs efficiently at high
redshift and as a technique for bolstering the sensitivity of LIM experiments,
even with a fraction of their total expected survey data.Comment: 15 pages, 8 figures. To be submitted to Ap
COMAP Early Science: VIII. A Joint Stacking Analysis with eBOSS Quasars
We present a new upper limit on the cosmic molecular gas density at z = 2.4 â 3.4 obtained using the first year of observations from the CO Mapping Array Project (COMAP). COMAP data cubes are stacked on the 3D positions of 243 quasars selected from the Extended Baryon Oscillation SpectroscopicSurvey (eBOSS) catalog, yielding a 95% upper limit for flux from CO(1-0) line emission of 0.129 Jykm/s. Depending on the balance of the emission between the quasar host and its environment, this value can be interpreted as an average CO line luminosity LâČCO of eBOSS quasars of †1.26 Ă 1011 K km pc2sâ1, or an average molecular gas density ÏH2 in regions of the universe containing a quasar of †1.52 Ă 108 Mâ cMpcâ3. The LâČ CO upper limit falls among CO line luminosities obtained fromindividually-targeted quasars in the COMAP redshift range, and the ÏH2 value is comparable to upper limits obtained from other Line Intensity Mapping (LIM) surveys and their joint analyses. Further, we forecast the values obtainable with the COMAP/eBOSS stack after the full 5-year COMAP Pathfinder survey. We predict that a detection is probable with this method, depending on the CO properties of the quasar sample. Based on the achieved sensitivity, we believe that this technique of stacking LIM data on the positions of traditional galaxy or quasar catalogs is extremely promising, both asa technique for investigating large galaxy catalogs efficiently at high redshift and as a technique for bolstering the sensitivity of LIM experiments, even with a fraction of their total expected survey data
UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from
1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The
data set comprises 2190 observations and is the largest homogeneously observed
and reduced sample of SN Ia to date, nearly doubling the number of
well-observed, nearby SN Ia with published multicolor CCD light curves. The
large sample of U-band photometry is a unique addition, with important
connections to SN Ia observed at high redshift. The decline rate of SN Ia
U-band light curves correlates well with the decline rate in other bands, as
does the U-B color at maximum light. However, the U-band peak magnitudes show
an increased dispersion relative to other bands even after accounting for
extinction and decline rate, amounting to an additional ~40% intrinsic scatter
compared to B-band.Comment: 84 authors, 71 pages, 51 tables, 10 figures. Accepted for publication
in the Astronomical Journal. Version with high-res figures and electronic
data at http://astron.berkeley.edu/~saurabh/cfa2snIa
COMAP Early Science: V. Constraints and Forecasts at
We present the current state of models for the carbon monoxide (CO)
line-intensity signal targeted by the CO Mapping Array Project (COMAP)
Pathfinder in the context of its early science results. Our fiducial model,
relating dark matter halo properties to CO luminosities, informs parameter
priors with empirical models of the galaxy-halo connection and previous CO(1-0)
observations. The Pathfinder early science data spanning wavenumbers
-Mpc represent the first direct 3D constraint on the
clustering component of the CO(1-0) power spectrum. Our 95% upper limit on the
redshift-space clustering amplitude K greatly
improves on the indirect upper limit of K reported from the CO
Power Spectrum Survey (COPSS) measurement at Mpc. The COMAP
limit excludes a subset of models from previous literature, and constrains
interpretation of the COPSS results, demonstrating the complementary nature of
COMAP and interferometric CO surveys. Using line bias expectations from our
priors, we also constrain the squared mean line intensity-bias product,
K, and the cosmic molecular gas
density, Mpc (95% upper
limits). Based on early instrument performance and our current CO signal
estimates, we forecast that the five-year Pathfinder campaign will detect the
CO power spectrum with overall signal-to-noise of 9-17. Between then and now,
we also expect to detect the CO-galaxy cross-spectrum using overlapping galaxy
survey data, enabling enhanced inferences of cosmic star-formation and
galaxy-evolution history.Comment: Paper 5 of 7 in series. 17 pages + appendix and bibliography (30
pages total); 15 figures, 6 tables; accepted for publication in ApJ; v3
reflects the accepted version with minor changes and additions to tex
- âŠ