Absolute Calibration of the Jason-1 Altimeter Using UK Tide Gauges

This article describes an “absolute” calibration of Jason-1 (J-1) altimeter sea surface height bias using a method developed for TOPEX/Poseidon (T/P) bias determination reported previously. The method makes use of U.K. tide gauges equipped with Global Positioning System (GPS) receivers to measure sea surface heights at the same time, and in the same geocentric reference frame, as Jason-1 altimetric heights recorded in the nearby ocean. The main time-dependent components of the observed altimeter-minus-gauge height-difference time series are due to the slightly different ocean tides at the gauge and in the ocean. The main harmonic coefficients of the tide differences are calculated from analysis of the copious TOPEX data set and then applied to the determination of T, P, and J-1 bias in turn. Datum connections between the tide gauge and altimetric sea surface heights are made by means of precise, local geoid differences from the EGG97 model. By these means, we have estimated Jason-1 altimeter bias determined from Geophysical Data Record (GDR) data for cycles 1-61 to be 12.9 cm, with an accuracy estimated to be approximately 3 cm on the basis of our earlier work. This J-1 bias value is in close agreement with those determined by other groups, which provides a further confirmation of the validity of our method and of its potential for application in other parts of the world where suitable tide gauge, GPS, and geoid information exist.     

Pollutant-induced cell injury in fish liver: Use of fluorescent molecular probes in live hepatocytes

This study was conducted to test whether live cells from the liver of fish could be used to detect early changes that are indicative of pollutant-induced liver damage. Low-molecular-weight fluorescent molecular probes were inserted into isolated hepatocytes from dab (Limanda limanda) from a contaminated site and a reference site in the North Sea. These included bioprobes for endoplasmic reticulum (ER), cytochrome P-450-associated 7-ethoxyresorufin-O-deethylase (EROD), oxyradicals, reduced glutathione (GSH) and microtubules (MT). Endocytosis of Texas Red-albumin was used as an integrated indicator of hepatocyte performance. Findings showed increases in ER-associated fluorescence, EROD and oxyradical generation, with a marked decrease in endocytosis in hepatocytes from fish caught at the contaminated site. These results indicate that fish from the historically contaminated site were impacted by organic xenobiotics which induced the biotransformation system, radical production and cell injury.     

Environmental prognostics: is the current use of biomarkers appropriate for environmental risk evaluation?

Environmental Prognostics is proposed as an integrated explanatory framework for adverse changes in whole systems, from cells to animals to ecosystems. The aim is to develop such frameworks for the evaluation of "health of the environment" and prediction of consequences resulting from future environmental events based on integrating the reactions of biomarkers for cellular and physiological processes, through conceptual, statistical and computational modelling. These are urgently needed to synthesise complex information on environmental chemistry and injurious effects of pollutants into predicted harmful impact on health of sentinel animals.     

Submarine groundwater discharge of nutrients to the ocean along a coastal lagoon barrier, Southern Brazil

The Patos–Mirim Lagoon system along the southern coast of Brazil is linked to the coastal ocean by a narrow mouth and by groundwater transport through a Holocene barrier. Although other groundwater systems are apparently active in this region, the hydraulic head of the lagoon, the largest in South America, drives groundwater transport to the coast. Water levels in wells placed in the barrier respond to changing water level in the lagoon. The wells also provide a measure of the nutrient concentrations of groundwater flowing toward the ocean. Additionally, temporary well points were used to obtain nutrient samples in groundwater on the beach face of the barrier. These samples revealed a subterranean freshwater–seawater mixing zone over a ca. 240 km shoreline. Previously published results of radium isotopic analyses of groundwater and of surface water from cross-shelf transects were used to estimate a water flux of submarine groundwater discharge (SGD) to nearshore surface waters of 8.5 × 10⁷ m³/day. Using this SGD and the nutrient concentrations in different compartments, nutrient fluxes between groundwater and surface water were estimated. Fluxes were computed using both average and median reservoir (i.e. groundwater and surface water) nutrient concentrations. The SGD total dissolved inorganic nitrogen, phosphate and silicate fluxes (2.42, 0.52, 5.92 × 10⁶ mol day^− 1, respectively) may represent as much as 55% (total N) to 10% (Si) of the nutrient fluxes to the adjacent shelf environment. Assuming nitrogen limitation, SGD may be capable of supporting a production rate of ca. 3000 g C m² year^− 1in the nearshore surf zone in this region.     

Lack of significant change in epiphyte biomass with increasing extent of measurement within seagrass meadows

A significant consideration in defining patterns of ecological interest is determining at what spatial scales these patterns are apparent. We performed a mensurative experiment to determine the effect of how changing the extent of sampling, using a fixed grain (panning up), changed our measurements of seagrass epiphyte biomass at a variety of hierarchical spatial scales, ranging from approximately 0.1 m to 2.5 × 10⁵ m. The experiment was performed twice at two sets of nested locations, also capturing an element of seasonality within the spatial extents. While the two regions and their nested locations differed in terms of epiphyte biomass, and values did change over time, mean epiphyte values were invariant at the local scale. This indicates that at the local scale (≤100 m extent), we expect seagrass epiphyte biomass to be relatively homogenous. Contrary to theoretical predictions, we did not detect predictable changes in mean values of epiphyte biomass as sampling extent increased. The results of this study highlight the importance of recognizing the spatial dependence of patterns in heterogeneous environments.     

The differential rotation of the corona as indicated by coronal holes

The rotation of the corona can be determined either directly by using Doppler methods or indirectly by using tracers, i.e., structures within the corona. In this study the rotational characteristics of the corona are determined using coronal holes as tracers, for the period 1978–1991. The coronal data used here are from an atlas of coronal holes mapped in Hei 10830 data. A comparison is made between our results and previous determinations of the coronal rotation rate, e.g., by Sime (1986), using white-light K-coronameter observations, by Timothy, Krieger, and Vaiana (1975), using soft X-ray observations, and by Shelke and Pande (1985) and Navarro-Peralta and Sanchez-Ibarra (1994), using Hei 10830 data. For the atlas of coronal holes used in this study the nature of the coronal hole distributions in number and latitude, in yearly averages, has been determined. These distributions show that at solar minimum the polar coronal holes dominate and the few non-polar holes are confined to a narrow band near the equator. At solar maximum, however, mid-latitude coronal holes dominate, with a large spread in latitudes. Given these distributions we consider the differential rotation data only as an average over a solar cycle. This removes spurious effects caused by having only a small number of coronal holes contributing to the results, or by having a narrow latitude band for the observations, thus limiting the results to that narrow latitude band. By considering these coronal holes as tracers of the differential rotation we show that the mid-latitude corona rotates more rigidly than the photosphere, but still exhibits significant differential rotation, with an equatorial rate of 13.30 ± 0.04° day^–1, and at 45° latitude a rate of 12.57 ± 0.13° day^–1. These results are comparable, within errors, to the Sime (1986) results which have an equatorial rate of approximately 13.2 ± 0.2° day^–1 and a rate of approximately 12.9 ± 0.3° day^–1 at 45° latitude.     

Composition and petrogenesis of oxide-, apatite-rich gabbronorites associated with Proterozoic anorthosite massifs: examples from the Adirondack Mountains,New York

Mafic dikes and sheets rich in Fe, Ti-oxides and apatite are commonly associated with Proterozoic massif anorthosites and are referred to as oxide-apatite gabbronorites (OAGN). Within the Adirondacks, field evidence indicates that during middle to late stages of anorthositic evolution, these bodies were emplaced as magmas with unspecified liquid-crystal ratios. Sixty whole rock analyses of Adirondack OAGN and related rocks define continuous oxide trends on Harker variation diagrams (SiO₂=37–54%). Similar trends exist for Sr, Y, Nb, Zr, and REE and together suggest a common origin via fractional crystallization. A representative parental magma (plagioclase-rich crystal mush) has been chosen from this suite, and successive daughter magmas have been produced by removal of minerals with compositions corresponding to those determined in actual rocks. Least squares, mass balance calculations of major element trends indicate that removal of intermediate plagioclase (An_40–50) plus lesser amounts of pyroxene account for the compositional variation of this suite and produce very low sums of the squares of the residuals (R² _s>0.25). The extracted mineral phases correspond volumetrically and compositionally to those of the anorthositic suite, and the model succeeds in accounting for the observed OAGN trends. The major element model is utilized to calculate trace elejent concentrations for successive magmas, and these agree closely with observation. We conclude that, beginning with a plagioclase-rich crystal mush, the extraction of intermediate plagioclase (An_40–50) drives residual magmas to increasingly Fe-, Ti-, and P-rich and SiO₂-poor conditions characteristic of Fenner-type fractionation. The crystallization sequence is plagioclaseplagioclase+orthopyroxeneplagioclase+orthopyroxene (pigeonite)+augite. Fe, Ti-oxides begin to crystallize near the end of the sequence and are followed by apatite and fayalitic olivine which appears in place of pigeonite. Augitic pyroxene becomes the dominant ferromagnesian phase in late stages of fractionation. Resultant OAGN magmas are injected into congealed anorthosite by filter pressing of liquid-rich interstitial fractions. Varying compositions of the dikes reflect filter pressing at different stages during fractionation and thereby provide information on the fractionation history of Proterozoic massif anorthosites.     

Cross-shore separation of adult and juvenile euphausiids in a shelf-break alongshore current

Euphausiids are an important component of the zooplankton in boundary current upwelling regions, including the Pacific Northwest continental margin. Many aspects of euphausiid distribution and ecology in this region are well known. However, some features of their spatial and temporal distribution are less understood:

• How and why euphausiids aggregate near the shelf-break upwelling center.

• How and why there is (within an alongshore band of high abundance of all stages) spatial segregation of adults and larvae.

• Why, despite spatial association with upwelling, euphausiid abundance off Vancouver Island is weakly or negatively correlated at interannual time scales with upwelling intensity.

To address these, we made km-resolution surveys of adult, juvenile, and larval euphausiid horizontal distributions, water properties, and currents across the Vancouver Island shelf break in mid-to-late spring of two successive years. Survey timing was before (1997) and after (1998) the spring transition to upwelling conditions, and near the annual spring reproductive peak. In both years, early developmental stages occupied an alongshore band that was offset from the late juveniles and adults. The direction of the offset differed between the two surveys. Early life history stages (larvae and early juveniles) were shoreward of adults in April 1997 (downwelling-conditions), but seaward of adults in May 1998 (upwelling-conditions). Separation distance (order 5–10 km) was consistent with expected differences in cumulative wind-driven (and vertically-sheared) cross-shore transport of surface-dwelling larvae and early juveniles vs. transport of diel migratory late juveniles and adults. Separation direction was consistent with recent history of winds and Ekman transport—shoreward during poleward winds, and seaward into blue water (and usually into a strong equatorward current) during equatorward winds.