Observations of near-surface ocean currents at varying depths using a new multifrequency HF radar

2002 ◽  
Author(s):  
J.F. Vesecky ◽  
C.C. Teague ◽  
R.G. Onstott ◽  
P. Hansen ◽  
N. Schnepf ◽  
...  
Keyword(s):  
Ocean Currents ◽  
Hf Radar ◽  
Near Surface ◽  
Surface Ocean

scholarly journals Linking sardine recruitment in coastal areas to ocean currents using surface drifters and HF radar: a case study in the Gulf of Manfredonia, Adriatic Sea

Ocean Science ◽  
2018 ◽  
Vol 14 (6) ◽  
pp. 1461-1482 ◽  
Author(s):  
Roberta Sciascia ◽  
Maristella Berta ◽  
Daniel F. Carlson ◽  
Annalisa Griffa ◽  
Monica Panfili ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Strong Dependence ◽  
Early Life History ◽  
Ocean Currents ◽  
Hf Radar ◽  
Residence Times ◽  
Sustainable Resource Management ◽  
Surface Ocean ◽  
Surface Drifters

Abstract. Understanding the role of ocean currents in the recruitment of commercially and ecologically important fish is an important step toward developing sustainable resource management guidelines. To this end, we attempt to elucidate the role of surface ocean transport in supplying recruits of European sardine (Sardina pilchardus) to the Gulf of Manfredonia, a known recruitment area in the Adriatic Sea. Sardine early life history stages (ELHSs) were collected during two cruises to provide observational estimates of their age–size relationship and their passive pelagic larval duration (PPLD). We combine these PPLDs with observations of surface ocean currents to test two hypotheses: (1) ELHSs are transported from remote spawning areas (SAs) by ocean currents to the Gulf of Manfredonia; (2) sardines spawn locally and ELHSs are retained by eddies. A historical surface drifter database is used to test hypothesis 1. Hypothesis 2 is tested by estimating residence times in the Gulf of Manfredonia using surface drifters and virtual particles trajectories that were computed from high-resolution observations of surface currents measured by a high-frequency (HF) radar network. Transport to the Gulf of Manfredonia from remote SAs seems more likely than local spawning and retention given a mismatch between observed PPLDs of 30–50 days and relatively short (<10-day) average residence times. The number and strength of connections between the gulf and remote SAs exhibit a strong dependence on PPLD. For PPLDs of 20 days or less, the gulf is connected to SAs on the western Adriatic coast through transport in the Western Adriatic Current (WAC). SAs on the east coast are more important at longer PPLDs. SAs in the northern and central Adriatic exhibit weak connections at all PPLD ranges considered. These results agree with otolith microstructure analysis, suggesting that the arrival of larvae in the gulf is characterized by repeated pulses from remote SAs. This is the first attempt to describe the processes related to Lagrangian connection to, and retention in, the Gulf of Manfredonia that will be complemented in the future using validated numerical ocean models and biophysical models.

scholarly journals Linking sardine recruitment in coastal areas to ocean currents using surface drifters and HF radar. A case study in the Gulf of Manfredonia, Adriatic Sea

2018 ◽  
Author(s):  
Roberta Sciascia ◽  
Maristella Berta ◽  
Daniel F. Carlson ◽  
Annalisa Griffa ◽  
Monica Panfili ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Early Life History ◽  
Ocean Currents ◽  
Hf Radar ◽  
Sustainable Resource Management ◽  
Surface Ocean ◽  
Spawning Areas ◽  
Surface Drifters ◽  
Particles Trajectories

Abstract. Understanding the role of ocean currents in the recruitment of commercially and ecologically important fish is an important step toward developing sustainable resource management guidelines. To this end, we attempt to elucidate the role of surface ocean transport in supplying recruits of European sardine (Sardinus pilchardus) to the Gulf of Manfredonia, a known recruitment area in the Adriatic Sea. Sardine early life history stages (ELHS) were collected during two cruises to provide observational estimates of age-size relationship and of their passive pelagic larval duration (PPLD). We combine these PPLDs with observations of surface ocean currents to test two hypotheses: (1) ELHS are transported from remote spawning areas (SAs) by ocean currents to the Gulf of Manfredonia; (2) sardines spawn locally and ELHS are retained by eddies. A historical surface drifter database is used to test hypotheses 1. Hypothesis 2 is tested by estimating residence times of surface drifters and virtual particles trajectories that were computed from high resolution observations of surface currents measured by a High Frequency (HF) radar network. Transport to the Gulf of Manfredonia from remote SAs seems more likely than local spawning and retention given a mismatch between observed PPLDs of 30–50 days and relatively short (

scholarly journals Wind, Waves, and Fronts: Frictional Effects in a Generalized Ekman Model

2016 ◽  
Vol 46 (2) ◽  
pp. 371-394 ◽  
Author(s):  
Jacob O. Wenegrat ◽  
Michael J. McPhaden
Keyword(s):  
Boundary Layer ◽  
Surface Waves ◽  
Ocean Currents ◽  
Surface Boundary ◽  
Pressure Gradients ◽  
Surface Boundary Layer ◽  
Near Surface ◽  
Thermal Wind ◽  
Surface Ocean ◽  
Wide Range

AbstractOcean currents in the surface boundary layer are sensitive to a variety of parameters not included in classic Ekman theory, including the vertical structure of eddy viscosity, finite boundary layer depth, baroclinic pressure gradients, and surface waves. These parameters can modify the horizontal and vertical flow in the near-surface ocean, making them of first-order significance to a wide range of phenomena of broad practical and scientific import. In this work, an approximate Green’s function solution is found for a model of the frictional ocean surface boundary layer, termed the generalized Ekman (or turbulent thermal wind) balance. The solution admits consideration of general, more physically realistic forms of parameters than previously possible, offering improved physical insight into the underlying dynamics. Closed form solutions are given for the wind-driven flow in the presence of Coriolis–Stokes shear, a result of the surface wave field, and thermal wind shear, arising from a baroclinic pressure gradient, revealing the common underlying physical mechanisms through which they modify currents in the ocean boundary layer. These dynamics are further illustrated by a case study of an idealized two-dimensional front. The solutions, and estimates of the global distribution of the relative influence of surface waves and baroclinic pressure gradients on near-surface ocean currents, emphasize the broad importance of considering ocean sources of shear and physically realistic parameters in the Ekman problem.

scholarly journals <i>Brief communication</i> "The 2013 Erebus Glacier tongue calving event"

2013 ◽  
Vol 7 (2) ◽  
pp. 1749-1760
Author(s):  
C. L. Stevens ◽  
P. Sirguey ◽  
G. H. Leonard ◽  
T. G. Haskell
Keyword(s):  
Ocean Circulation ◽  
Ocean Currents ◽  
Mcmurdo Sound ◽  
Glacier Tongue ◽  
Surface Ocean ◽  
Fast Ice

Abstract. The Erebus Glacier Tongue, a~small floating glacier in southern McMurdo Sound, is one of the best-studied ice tongues in Antarctica. Despite this, its calving on the 27 February 2013 (UTC) was around 10 yr earlier than previously predicted. The calving was likely a result of ocean currents and the absence of fast ice. The subsequent trajectory of the newly-created iceberg supports previous descriptions of the surface ocean circulation in southern McMurdo Sound.

scholarly journals Strongly Coupled Assimilation of a Hypothetical Ocean Current Observing Network within a Regional Ocean-Atmosphere Coupled Model: An OSSE Case Study of Typhoon Hato

2021 ◽  
Author(s):  
Luke Phillipson ◽  
Yi Li ◽  
Ralf Toumi
Keyword(s):  
Coupled Model ◽  
Ocean Currents ◽  
Hf Radar ◽  
Ocean Current ◽  
Coastal Current ◽  
Strongly Coupled ◽  
Ocean Atmosphere ◽  
Atmospheric Observations ◽  
Surface Drifters ◽  
The Impact

AbstractThe forecast of tropical cyclone (TC) intensity is a significant challenge. In this study, we showcase the impact of strongly coupled data assimilation with hypothetical ocean currents on analyses and forecasts of Typhoon Hato (2017). Several observation simulation system experiments were undertaken with a regional coupled ocean-atmosphere model. We assimilated combinations of (or individually) a hypothetical coastal current HF radar network, a dense array of drifter floats and minimum sea-level pressure. During the assimilation, instant updates of many important atmospheric variables (winds and pressure) are achieved from the assimilation of ocean current observations using the cross-domain error covariance, significantly improving the track and intensity analysis of Typhoon Hato. As compared to a control experiment (with no assimilation), the error of minimum pressure decreased by up to 13 hPa (4 hPa / 57 % on average). The maximum wind speed error decreased by up to 18 knots (5 knots / 41 % on average). By contrast, weakly coupled implementations cannot match these reductions (10% on average). Although traditional atmospheric observations were not assimilated, such improvements indicate there is considerable potential in assimilating ocean currents from coastal HF radar, and surface drifters within a strongly coupled framework for intense landfalling TCs.

scholarly journals Stable near-surface ocean salinity stratifications due to evaporation observed during STRASSE

2014 ◽  
Vol 119 (5) ◽  
pp. 3219-3233 ◽  
Author(s):  
William E. Asher ◽  
Andrew T. Jessup ◽  
Dan Clark
Keyword(s):  
Near Surface ◽  
Surface Ocean ◽  
Ocean Salinity

What is gradualism? Cryptic speciation in globorotaliid foraminifera

Paleobiology ◽  
1996 ◽  
Vol 22 (3) ◽  
pp. 386-405 ◽  
Author(s):  
Richard D. Norris ◽  
Richard M. Corfield ◽  
Julie Cartlidge
Keyword(s):  
Reproductive Isolation ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Reproductive Ecology ◽  
Shell Growth ◽  
Shell Shape ◽  
Planktic Foraminifera ◽  
Near Surface ◽  
Surface Ocean ◽  
Speciation Event

Analysis of the evolution of the Globorotalia (Fohsella) lineage of planktic foraminifera suggests that reproductive ecology and shell shape have evolved independently in this group. The silhouette of fohsellid shells displays a nearly unbroken anagenetic trend, yet isotopic data show that the fohsellids changed their depth of reproduction during the anagenetic evolution of their skeletons. Remarkably, there are no correlations between anagenesis in skeletal shape and the establishment of reproductive isolation. Apparently, anagenesis masks at least one speciation event that is apparent only in the isotopic evidence for a change in reproductive ecology. Although anagenetic trends have been widely cited as evidence for gradual speciation in planktic foraminifera and other microfossil groups, our data suggest that they should not always be considered to record either the tempo or mode of speciation.Speciation was apparently uncoupled from morphological evolution in fohsellids because these evolutionary phenomena occurred in different phases of ontogeny. Gradual morphological changes were associated with the main phase of shell growth of both the ancestor and descendant species in the near-surface ocean. Reproductive isolation occurred when ancestral and descendant populations became established at different depths near the end of the life cycle. Morphological evolution may also be uncoupled from reproductive isolation in other organisms that experience very different selection pressures over the duration of their ontogenies, such as parasites with many hosts, species with multiple phases of metamorphosis, and organisms that broadcast their gametes.

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