29 research outputs found
nearshore-exchange toolbox
No full text<p>A set of functions to compute cross-shore exchange velocities for various nearshore processes as a function of environmental conditions. Example included to produce Figure 11 in Moulton et al., 2023.</p>
<p><strong>References</strong></p>
<ul>
<li>Moulton, M., S.H. Suanda, J.C. Garwood, N. Kumar, M.R. Fewings, and J.M. Pringle. 2023. Exchange of plankton, pollutants, and particles across the nearshore region. Annual Review of Marine Science, <em>15</em>(1), 1–36, doi:10.1146/annurev-marine-032122-115057.</li>
</ul>
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Diurnal wind-driven processes on the northern Monterey Bay inner shelf
No full textIn the summer of 2007, a biophysical experiment was conducted to identify physical processes that determine the delivery of invertebrate larvae and juvenile rockfish to rocky intertidal and kelp forest communities in northern Monterey Bay, California. The experiment was sponsored by the Partnership for Interdisciplinary
Studies of Coastal Oceans (PISCO) and collected physical measurements including velocity from acoustic Doppler current profilers, surface gravity wave heights measured acoustically, and temperature from thermistor chain arrays both along- and
across- the inner shelf in water depths of 10 – 60 m. The inner shelf is the transition between the nearshore and mid-shelf zones, and is defined where surface and bottom
Ekman boundary layers overlap. Previous work has shown that the inner shelf in this region is rich in physical processes across many space and time scales. The goal here is to identify and quantify the dominant processes at the diurnal (24 hour) period. Diurnal tides contribute less than 10% of the observed currents. Thus the focus is on the oceanic response to a strong (8 - 15 m/s daily maximum) along-shelf sea breeze which forces offshore surface Ekman transport, drives average upwelling velocities of 26 m/day, and cools the water column 2 – 4 degrees/day. At 15 m (20 m) depth, measured diurnal surface transport
is 36% ± 9% (77% ± 12%) of full theoretical Ekman transport. Examination of a diurnal heat budget shows that vertical advection is the dominant process during afternoon cooling (both horizontal advection and solar insolation are sources of heat
during this period), and is needed to close the heat budget to within 5%. In contrast, during evening/early morning heating 92% of the observed heating is explained by along-shelf advection of a temperature gradient within the upwelling shadow, much
greater than the heating attributed to either solar insolation (2%) or onshore motions (2%). Thus, the diurnal heat budget is closed to within a few percent and explained by
two-dimensional processes: vertical advection by wind-driven upwelling during cooling and along-shelf advection during heating.Keywords: Inner shelf, Monterey Bay, coastal, wind-driven, physical oceanograph
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Tidal-band and high-frequency internal variability on the central Oregon inner shelf
No full textAnalogous to ocean surface waves, waves in the ocean interior also experience steepening, breaking, and dissipation as they approach the coastline. Much less is known about this internal beach. In this work, extensive moored Acoustic Doppler Current Profiler and temperature/salinity data together with optical remote sensing are combined to describe and understand tidal-band and high-frequency internal wave propagation over the Oregon mid and inner shelf. Semidiurnal baroclinic velocity is dominated by the first mode at all locations, with larger velocities on the mid shelf and northern part of a large submarine bank. Mid-shelf sites have baroclinic ellipticity that is near the theoretical value for single, progressive internal tidal waves compared to more linearly polarized currents over the inner shelf. Temporal variability does not correspond to the spring-neap cycle and is overall uncorrelated between mooring locations due to variable along-shelf topography and stratification. An idealized model of two amplitude-modulated internal waves propagating from different directions reproduces some of the observed variability in inner-shelf semidiurnal ellipse parameters. Moored observations were combined with sea-surface imagery to describe the propagation of 11 bore-like internal waves across the inner shelf. The surface expression of these waves is identified by regions of increased pixel intensity during wind speeds between 2 - 5 m/s⁻¹. Optical measurements show that internal waves are refracted by bathymetry, and measured wave speed (~0.15 m/s) is higher than predicted by linear theory (< 0.1 m/s⁻¹). The number and strength of these high-frequency (15 minute period), highly nonlinear features are linked to regional-scale upwelling/downwelling as well as the phase of the mid-shelf internal tide. In general, both surface and bottom-trapped bores are observed on the inner shelf and their polarity can be predicted by the weakly nonlinear parameter of the Korteweg-de Vries wave propagation equation. These bores have different consequences for the amount of horizontal transport they accomplish and where in the water column this transport occurs. The transformation of the internal tide impacts the form of the nonlinear high-frequency oscillations observed on the inner shelf. The most efficient onshore transport of sub-thermocline water is observed during a shallow mid-shelf pycnocline with large mid-shelf semidiurnal displacement that results in only elevation waves onshore
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Semidiurnal Baroclinic Tides on the Central Oregon Inner Shelf
No full textSemidiurnal velocity and density oscillations are examined over the mid- and inner continental shelf near Heceta Bank on the Oregon coast. Measurements from two long-term observation networks with sites on and off the submarine bank reveal that both baroclinic velocities and displacements are dominated by the first mode, with larger velocities on the midshelf and northern parts of the bank. Midshelf sites have current ellipses that are near the theoretical value for single, progressive internal tidal waves compared to more linearly polarized currents over the inner shelf. Baroclinic current variability is not correlated to the spring-neap cycle and is uncorrelated between mooring locations. An idealized model of two internal waves propagating from different directions reproduces some of the observed variability in semidiurnal ellipse parameters. At times, the phasing between moorings along a cross-shelf transect are consistent with onshelf wave propagation, a characteristic also present in the output of a three-dimensional regional circulation model. Regional wind-driven upwelling/downwelling influences stratification at all shelf moorings. At locations north of the bank, stronger baroclinic velocities were found during periods of higher background stratification.Keywords: Circulation, Upwelling, Baroclinic flows, Geographic location, downwelling, entity, Internal waves, slope, Continental shelf, Dynamic
Design of a quantum well based on a ZnCdSe/ZnTe type II heterostructure confined type I within ZnSe barriers
No full textStatistics of internal tide bores and internal solitary waves observed on the inner continental shelf off Point Sal, California
No full textManuscript received 6 March 2017, in final form 31 July 2017The article of record as published may be located at http://journals.ametsoc.org/doi/full/10.1175/JPO-D-17-0045.1Moored observations of temperature and current were collected on the inner continental shelf off Point Sal,
California, between 9 June and 8 August 2015. The measurements consist of 10 moorings in total: 4 moorings
each on the 50- and 30-m isobaths covering a 10-km along-shelf distance and an across-shelf section of
moorings on the 50-, 40-, 30-, and 20-m isobaths covering a 5-km distance. Energetic, highly variable, and
strongly dissipating transient wave events termed internal tide bores and internal solitary waves (ISWs)
dominate the records. Simple models of the bore and ISW space–time behavior are implemented as a temperature
match filter to detect events and estimate wave packet parameters as a function of time and mooring
position. Wave-derived quantities include 1) group speed and direction; 2) time of arrival, time duration,
vertical displacement amplitude, and waves per day; and 3) energy density, energy flux, and propagation loss.
In total, over 1000 bore events and over 9000 ISW events were detected providing well-sampled statistical
distributions. Statistics of the waves are rather insensitive to position along shelf but change markedly in the
across-shelf direction. Two compelling results are 1) that the probability density functions for bore and ISW
energy flux are nearly exponential, suggesting the importance of interference and 2) that wave propagation loss
is proportional to energy flux, thus giving an exponential decay of energy flux toward shore with an e-folding
scale of 2–2.4 km and average dissipation rates for bores and ISWs of 144 and ¯ ¹, respectively.N0001417WX01136N00014-17-1-2890OCE-1521653N0017317WR00125Office of Naval ResearchNational Science Foundatio
Drivers of seasonal to decadal mixed layer carbon cycle variability in subantarctic water in the Munida Time Series
No full textUsing ancillary datasets and interpolation schemes, 20+ years of the Munida Time Series (MTS) observations were used to evaluate the seasonal to decadal variability in the regional carbon cycle off the southeast coast of New Zealand. The contributions of gas exchange, surface freshwater flux, physical transport processes and biological productivity to mixed layer carbon were diagnostically assessed using a mass-balanced surface ocean model. The seasonal and interannual variability in this region is dominated by horizontal advection of water with higher dissolved inorganic carbon (DIC) concentration primarily transported by the Southland Current, a unique feature in this western boundary current system. The large advection term is primarily balanced by net community production and calcium carbonate production, maintaining a net sink for atmospheric CO2 with a mean flux of 0.84±0.62 mol C m-2 y-1. However, surface layer pCO2 shows significant decadal variability, with the growth rate of 0.53±0.26 matm yr-1 during 1998–2010 increasing to 2.24±0.47 matm yr-1 during 2010–2019, driven by changes in advection and heat content. Changes in circulation have resulted in the regional sink for anthropogenic CO2 being 50% higher and pH 0.011±.003 higher than if there had been no long-term changes in circulation. Detrended cross-correlation analysis was used to evaluate correlations between the Southern Annular Mode, the Southern Oscillation Index and various regional DIC properties and physical oceanographic processes over frequencies corresponding the duration of the MTS. The drivers of variability in the regional carbon cycle and acidification rate indicate sensitivity of the region to climate change and associated impacts on the Southern Ocean and South Pacific
Statistics of Internal Tide Bores and Internal Solitary Waves Observed on the Inner Continental Shelf off Point Sal, California
No full textAbstractMoored observations of temperature and current were collected on the inner continental shelf off Point Sal, California, between 9 June and 8 August 2015. The measurements consist of 10 moorings in total: 4 moorings each on the 50- and 30-m isobaths covering a 10-km along-shelf distance and an across-shelf section of moorings on the 50-, 40-, 30-, and 20-m isobaths covering a 5-km distance. Energetic, highly variable, and strongly dissipating transient wave events termed internal tide bores and internal solitary waves (ISWs) dominate the records. Simple models of the bore and ISW space–time behavior are implemented as a temperature match filter to detect events and estimate wave packet parameters as a function of time and mooring position. Wave-derived quantities include 1) group speed and direction; 2) time of arrival, time duration, vertical displacement amplitude, and waves per day; and 3) energy density, energy flux, and propagation loss. In total, over 1000 bore events and over 9000 ISW events were detected providing well-sampled statistical distributions. Statistics of the waves are rather insensitive to position along shelf but change markedly in the across-shelf direction. Two compelling results are 1) that the probability density functions for bore and ISW energy flux are nearly exponential, suggesting the importance of interference and 2) that wave propagation loss is proportional to energy flux, thus giving an exponential decay of energy flux toward shore with an e-folding scale of 2–2.4 km and average dissipation rates for bores and ISWs of 144 and 1.5 W m−1, respectively.</jats:p
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Shore-Based Video Observations of Nonlinear Internal Waves across the Inner Shelf
No full textShore-based video remote sensing is used to observe and continually monitor nonlinear internal waves
propagating across the inner shelf. Month-long measurements of velocity from bottom-mounted acoustic
Doppler current profilers and temperature from thermistor chains at the 10- and 20-m isobaths are combined
with sea surface imagery from a suite of cameras (Argus) to provide a kinematic description of 11 borelike
internal waves as they propagate across the central Oregon inner shelf. The surface expression of these waves,
commonly seen by eye as alternating rough and smooth bands, are identified by increased pixel intensity in
Argus imagery (average width 39 ± 6 m), caused by the convergence of internal wave-driven surface currents.
These features are tracked through time and space using 2-min time exposure images and then compared to
wave propagation speed and direction from in situ measurements. Internal waves are refracted by bathymetry,
and the measured wave speed (~0.15 m s⁻¹) is higher than predicted by linear theory (< 0.1 m s⁻¹).
Propagating internal waves are also visible in subsampled Argus pixel time series (hourly collections of 17 min
worth of 2-Hz pixel intensity from a subset of locations), thus extending the observational record to times
without an in situ presence. Results from this 5-month record show that the preferred sea state for successful
video observations occurs for wind speeds of 2–5 m s⁻¹. Continued video measurements and analysis of extensive
existing Argus data will allow a statistical estimate of internal wave occurrence at a variety of inner-shelf
locations.Keywords: Internal waves, Remote sensing, Continental shelf/slop
