George A. Maul

Cyclonic Eddies in the Eastern Gulf of Mexico

Abstract Cold-domed cyclonic eddies juxtaposed to the cyclonic shear side of the Gulf Loop Current are observed in simultaneously obtained hydrographic, current meter mooring, and satellite infrared data. The cyclones are initially observed in the satellite data as cold perturbations on the northern extreme of the current and grow either into a cold tongue or a quasi-stable meander off the Dry Tortugas Florida. Areal shipboard surveys show closed isopleths of temperature and salinity, and surface geostrophic current speeds relative to 1000 db are in excess of 100 cm s−1. The diameter of the cold domes varied from 80 to 120 km. Separation of large anticyclonic rings is always observed to be preceded by cyclonic eddies in the transition zone between Campeche Bank and the West Florida Shelf, but only on the eastern side. Not every cyclonic eddy off Dry Tortups is associated with the separation of an anticyclonic ring; some are eroded away by the Florida Current, but they have never been observed in 10 years ...

Anticyclonic current rings in the eastern tropical Pacific Ocean

Observations from satellite-tracked drifting buoys, expendable bathythermograph and conductivity-temperature-depth data, and Geosat altimeter data are used to describe anticyclonic eddies that occur in small numbers off the Pacific coast of Central America. These eddies are similar in many respects to the well-known warm-core rings that are observed north of the Gulf Stream off the Atlantic coast of North America, except that they occur in an environment that also is warm, and they contain considerably greater kinetic energy. It is hypothesized that they are formed as a result of conservation of potential vorticity when the North Equatorial Countercurrent (NECC) turns northward upon approaching the eastern boundary during its autumnal maximum. The rings so formed have a strongly nonlinear character which causes them to propagate westward between 9°N and 14°N with a speed in excess of that of long Rossby waves. Due to a relatively small available potential energy content, these rings have a dissipation time scale of about 6 months and perhaps end by collision with and reabsorbtion into the NECC. The rings account for the observed enhancement of surface kinetic energy, and probably for the seaward transport of waters enriched in copper.

The Relationship between Variations in the Gulf of Mexico Loop Current and Straits of Florida Volume Transport

Abstract Twelve years of monthly mean positions of the northern boundary of the Loop Current in the eastern Gulf of Mexico from satellite and in situ data have been compared with coincident 1977–1988 estimates of volume transport in the Straits of Florida in the subseasonal frequency band 15−1 to 5−1 cycles per month. Volume transport estimated from Cuba minus Florida sea level difference in this frequency band accounts for 69% of the variance in volume transport estimated from the Florida-Grand Bahama Island submarine cable. On average, the Loop Current has a dominant period of 11 months whereas the volume transport is dominated by annual spectral energy; little significant coherence squared occurs between them. The maximum northward penetration of the Loop Current occurs on average in winter when the volume transport is a minimum, but this is an artifact of the sampling epoch. This negative relationship is most pronounced for 1979–1981 when transport is characterized as unimodal, but for 1984–1985 and 1...

On the Use of the Earth Resources Technology Satellite ( LANDSAT-1 ) in Optical Oceanography

Abstract Observations of the Gulf Stream System in the Gulf of Mexico were obtained in synchronization with LANDSAT-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed by color (diffuse radiance) or sea state (specular radiance) effects associated with the cyclonic boundary even in the absence of a surface thermal signature. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance. These calculations compare favorably with experimental measurements and show that the ratio of channels method gives ambiguous interpretative results. The results are used to discuss features in images where surface measurements were obtained and are extended to tentative explanation in others.

CARBON AND OXYGEN ISOTOPE TIME SERIES FROM AN 18-YEAR CARIBBEAN REEF CORAL

Colonies of Montastrea annularis live near La Parguera, Puerto Rico, and may be 700 years old. Time series from 1964 to 1982 of δ13C and δ18O from a continuous core of these corals are compared to an adjacent environmental record. At the intraannual level, δ18O correlates well with water temperature. Changes in the amplitude of the δ18O signal between 1967 and 1976 are attributed to sampling frequency but may be also due to environmental changes such as salinity. Average annual δ18O, δ13C and sea surface temperature show similar trends for the period from 1964 to 1982 but especially from 1969 onwards. Changes in average annual values during this time interval are most likely due to water mass changes brought about by interannual variability of the North Atlantic circulation. Since water temperatures at La Parguera are representative of changes occurring in the wider Caribbean, the isotope record from La Parguera corals could be used as a proxy for large-scale environmental changes beyond the historical record through the Little Ice Age.

Subtropical Atlantic Climate Studies: Introduction

This report is an introduction to the accompanying collection of reports that present the results of a 2-year period of intensive monitoring of the Florida Current. Both direct observing systems (ship-deployed current profilers and moored current meters) and indirect observing systems (coastal tide gauge stations, bottom pressure gauge arrays, a submarine cable, acoustic arrays, and radar installations) were used to measure temperature and volume transport.

Winter Intrusions of the Loop Current

Sea-surface temperature data obtained from satellite and subsurface temperature data obtained from ships are used to determine the intrusion of the The Loop Current extended considerably farther to the north during the last three winters than has been observed previously.

Sea Level Variation as an Indicator of Florida Current Volume Transport: Comparisons with Direct Measurements

Sea level measurements from tide gauges at Miami, Florida, and Cat Cay, Bahamas, and bottom pressure measurements from a water depth of 50 meters off Jupiter, Florida, and a water depth of 10 meters off Memory Rock, Bahamas, were correlated with 81 concurrent direct volume transport observations in the Straits of Florida. Daily-averaged sea level from either gauge on the Bahamian side of the Straits was poorly correlated with transport. Bottom pressure off Jupiter had a linear coefficient of determination ofr2 = 0.93, and Miami sea level, when adjusted for weather effects, had r2 = 0.74; the standard errors of estimating transports were � 1.2 x 106 and � 1.9 x 106 cubic meters per second, respectively. A linear multivariate regression, which combined bottom pressure, weather, and the submarine cable observations between Jupiter and the Bahamas, had r2 = 0.94 with a standard error of estimating transport of � 1.1 x 106 cubic meters per second. These results suggest that a combination of easily obtained observations is sufficient to adequatelv monitor the daily volume transport fluctuations of the Florida Current.

Zenith angle effects in multichannel infrared sea surface remote sensing

Abstract Several approaches to infrared multichannel sea surface temperature retrievals propose using a universal set of constants. It is shown that the single-channel multiangle technique (i.e., GOES and NOAA) and the multichannel single-angle technique (NOAA-n) are similar concepts with a common derivation from radiative transfer theory. It is also shown that the linear correlation factor between surface temperature minus satellite temperature in one channel versus the difference in satellite temperatures in two channels is not independent of the difference in satellite sensed equivalent blackbody temperature. The 3.7-μm, 11-μm, and 12-μm channels on the NOAA-n AVHRR can be used in combination to compute atmospheric transmissivity and average atmospheric temperature, but a better combination would be substituting three 0.5-μm-wide channels centered on 11.25 μm, 11.75 μm, and 12.25 μm. A triple window multispectral scanner in the 11–12.5 μm region allows determination of diffuse surface reflectance which can bias sea surface temperatures −0.4 K±0.3 K .

Interannual coherence between North Atlantic atmospheric surface pressure and composite southern U.S.A. sea level

Annual mean sea levels along the southern United States have been examined for interannual variability. Fifteen sea level stations from Cape Hatteras to the Rio Grande that best covered the three lunar nodal cycles from 1931–1987 were selected for analysis. Linear trends, ranging from +0.2 cm/yr to +1.4 cm/yr were subtracted from their respective series, leaving remarkably similar residuals. The composite time series of the 15 residuals was compared with time series of surface air pressure over the North Atlantic Ocean during the period 1947–1987. The best correlation is a negative relationship between composite sea level and wintertime air pressure north of 45°N, and a positive relationship from 20°–45°N. The most significant correlations (−0.73 and +0.51) were found for 60°N, 20°W and for 30°N, 25°W respectively. Wintertime meridional air pressure gradient between these two latitudes represents about 50% of the variance in composite annual mean sea level. Both the sea level and air pressure time series had significant spectral peaks at 13.3 and 4.4 years, with about 52% of the covariance coming from these two periods.