RRS Charles Darwin Cruise 141, 01 Jun-11 Jul 2002. Satellite Calibration and Interior Physics of the Indian Ocean: SCIPIO

RRS Charles Darwin Cruise 141, SCIPIO (Satellite Calibration and Interior Physics of the Indian Ocean) provided a multidisciplinary survey of the Mascarene Ridge system in the western Indian Ocean. The principal objectives were to (a) study the flow of water masses through the Ridge system, together with their decadal-timescale variability, (b) assess the energy fluxes and mixing arising from internal waves, (c) collect in situ data for the calibration of sea-surface temperature and ocean colour sensors on the ENVISAT satellite, (d) investigate the biogeochemical properties of the water masses, and (e) measure the heat fluxes and winds, and the airflow disturbance around the ship. The survey comprised three sections parallel with the Ridge near 64°, 60° and 57° E, joined by two other sections at 8° and 20°S. The sections comprised CTD, LADCP, and biogeochemistry (nutrients, phytoplankton, zooplankton, biogenic gases, CFC tracers and light levels) stations to full ocean depth, at typical spacings of about 60-80 nm. At several of these the CTD and LADCP were cycled continuously for a semidiurnal tidal cycle to study the internal waves, and the smaller 12-bottle CTD frame was used throughout (usually with 6 bottles) in order to reduce mixing effects from the trailing wake. Underway measurements were made with the shipboard ADCP, TSG, radiosondes, XBTs, and of surface meteorology, skin surface temperature, and zooplankton. The ship's EM12 swath bathymetry system was operated continuously, and used to study certain key areas in detail. In addition, MMP (a cycling CTD) and bottom-mounted ADCP moorings were successfully laid and recovered near 8°S, 60°E, and a first deployment of the ARGODOT turbulence probe was made near 20°S, 57.5°E

Aspects of the circulation in the Rockall Trough

An investigation is made of the circulation and structure of the water masses in the Rockall Trough in spring, combining the results of a recent synoptic survey (May 1998) with those from a high-resolution ocean circulation model. In the near-surface layer, saline flows are carried northwards by a "Shelf Edge Current" around the eastern slopes, possibly with some branching in the northern Trough. Fresher waters from the west inflow between 52 and 538N and partially mix with these saline flows in the southern Trough, so that waters of intermediate salinity are also swept northwards. In the southern approaches to the Trough, Labrador Sea Water (LSW) also flows strongly in from the west between 52 and 538N, and while much of this turns south, a proportion penetrates north to join a cyclonic gyre in the Trough extending to 56.58N. The northwestern limb of this gyre is fed by, and mixes with, more saline waters which result from overflows across the Wyville–Thomson Ridge. Furthermore, salinity and CFC data suggest episodic inflow of LSW into the central Trough. The circulation of the North East Atlantic Deep Water in the Trough follows a cyclonic pattern similar to, and lying below, that of the LSW. The Wyville–Thomson Ridge overflows in the model extend to higher densities than in the survey, are topographically steered southwestward down the Feni Ridge system, and eventually join a deep cyclonic circulation in the North East Atlantic basin. Overall, the model and the observations are in good agreement, particularly in the central Rockall Trough, and this has allowed conclusions to be drawn which are significantly more robust than those which would result from either the survey or the model alone. In particular, we have been able to infer cyclonic circulation pathways for the intermediate and deeper waters in the Rockall Trough for (we believe) the first time. The study has also contributed to an ongoing community effort to assess the realism of, and improve, our current generation of ocean circulation models

Far-field connectivity of the UK's four largest marine protected areas: Four of a kind?

Marine Protected Areas (MPAs) are established to conserve important ecosystems and protect marine species threatened in the wider ocean. However, even MPAs in remote areas are not wholly isolated from anthropogenic impacts. “Upstream” activities, possibly thousands of kilometers away, can influence MPAs through ocean currents that determine their connectivity. Persistent pollutants, such as plastics, can be transported from neighboring shelf regions to MPAs, or an ecosystem may be affected if larval dispersal is reduced from a seemingly remote upstream area. Thus, improved understanding of exactly where upstream is, and on what timescale it is connected, is important for protecting and monitoring MPAs. Here, we use a high-resolution (1/12°) ocean general circulation model and Lagrangian particle tracking to diagnose the connectivity of four of the UK's largest MPAs: Pitcairn; South Georgia and Sandwich Islands; Ascension; and the British Indian Ocean Territory (BIOT). We introduce the idea of a circulation “connectivity footprint”, by which MPAs are connected to upstream areas. Annual connectivity footprints were calculated for the four MPAs, taking into account seasonal and inter-annual variability. These footprints showed that, on annual timescales, Pitcairn was not connected with land, whereas there was increasing connectivity for waters reaching South Georgia, Ascension, and, especially, BIOT. BIOT also had a high degree of both seasonal and inter-annual variability, which drastically changed its footprint, year-to-year. We advocate that such connectivity footprints are an inherent property of all MPAs, and need to be considered when MPAs are first proposed or their viability as refuges evaluated

Role of carbon dioxide and ion transport in the formation of sub-embryonic fluid by the blastoderm of the Japanese quail

1. The explanted blastoderm of the Japanese quail was used to explore the role of ions and carbon dioxide in determining the rate of sub-embryonic fluid (SEF) production between 54 and 72 h of incubation. 2. Amiloride, an inhibitor of Na+/H+ exchange, at concentrations of 10-3 to 10-6 M substantially decreased the rate of SEF production when added to the albumen culture medium. N-ethylmaleimide, an inhibitor of V type H+ ATPase, also decreased this rate but only to a small extent at the highest dose applied, 10-3 M. Both inhibitors had no effect on SEF production when added to the SEF. 3. The inhibitors of cellular bicarbonate and chloride exchange, 4-acetamido-4-'isothiocyano-2, 2-'disulphonic acid (SITS) and 4,4'diisothiocyanostilbene-2,2-'disulphonic acid (DIDS), had no effect upon SEF production. 4. Ouabain, an inhibitor of Na+/K+ ATPase, decreased SEF production substantially at all concentrations added to the SEF (10-3 to 10-6 M). Three sulphonamide inhibitors of carbonic anhydrase, acetazolamide, ethoxzolamide and benzolamide, decreased SEF production when added to the SEF at concentrations of 10-3 to 10-6 M. Benzolamide was by far the most potent. Neither ouabain nor the sulphonamides altered SEF production when added to the albumen culture medium. 5. Using a cobalt precipitation method, carbonic anhydrase activity was localised to the endodermal cells of the area vasculosa. The carbonic anhydrase activity was primarily associated with the lateral plasma membranes, which together with the potent inhibitory effect of benzolamide, suggests the carbonic anhydrase of these cells is the membrane-associated form, CA IV. 6. The changes in SEF composition produced by inhibitors were consistent with the production of SEF by local osmotic gradients. 7. It is concluded that a Na+/K+ ATPase is located on the basolateral membranes of the endodermal cells of the area vasculosa , and that a sodium ion/hydrogen ion exchanger is located on their apical surfaces. Protons for this exchanger would be provided by the hydration of CO2 catalysed by the membrane-associated carbonic anhydrase. Furthermore, it is proposed that the prime function of the endodermal cells of the area vasculosa is the production of SEF

Few cycle pulse propagation

We present a comprehensive framework for treating the nonlinear interaction of few-cycle pulses using an envelope description that goes beyond the traditional SVEA method. This is applied to a range of simulations that demonstrate how the effect of a $\chi^{(2)}$ nonlinearity differs between the many-cycle and few-cycle cases. Our approach, which includes diffraction, dispersion, multiple fields, and a wide range of nonlinearities, builds upon the work of Brabec and Krausz[1] and Porras[2]. No approximations are made until the final stage when a particular problem is considered. The original version (v1) of this arXiv paper is close to the published Phys.Rev.A. version, and much smaller in size.Comment: 9 pages, 14 figure

On the origin and pathway of the saline inflow to the Nordic Seas: insights from models

The behaviours of three high-resolution ocean circulation models of the North Atlantic, differing chiefly in their description of the vertical coordinate, are investigated in order to elucidate the routes and mechanisms by which saline water masses of southern origin provide inflows to the Nordic Seas. An existing hypothesis is that Mediterranean Overflow Water (MOW) is carried polewards in an eastern boundary undercurrent, and provides a deep source for these inflows. This study, however, provides an alternative view that the inflows are derived from shallow sources, and are comprised of water masses of western origin, carried by branches of the North Atlantic Current (NAC), and also more saline Eastern North Atlantic Water (ENAW), transported northwards from the Bay of Biscay region via a ‘Shelf Edge Current’ (SEC) flowing around the continental margins. In two of the models, the MOW flows northwards, but reaches only as far as the Porcupine Bank (53°N). In third model, the MOW also invades the Rockall Trough (extending to 60°N). However, none of the models allows the MOW to flow northwards into the Nordic Seas. Instead, they all support the hypothesis of there being shallow pathways, and that the saline inflows to the Nordic Seas result from NAC-derived and ENAW water masses, which meet and partially mix in the Rockall Trough. Volume and salinity transports into the southern Rockall Trough via the SEC are, in the various models, between 25 and 100% of those imported by the NAC, and are also a similarly significant proportion (20–75%) of the transports into the Nordic Seas. Moreover, the highest salinities are carried northwards by the SEC (these being between 0.13 and 0.19 psu more saline at the southern entrance to the Trough than those in the NAC-derived waters). This reveals for the first time the importance of the SEC in carrying saline water masses through the RockallTrough and into the Nordic Seas. Furthermore, the high salinities found on density surfaces appropriate to the MOW in the Nordic Seas are shown to result from the wintertime mixing of the saline near-surface waters advected northwards by the SEC/NAC system. Throughout, we have attempted to demonstrate the extent to which the models agree or disagree with interpretations derived from observations, so that the study also contributes to an ongoing community effort to assess the realism of our current generation of ocean models

Higher bone resorption excretion in South Asian women vs. White Caucasians and increased bone loss with higher seasonal cycling of vitamin D: Results from the D-FINES cohort study

Few data exist on bone turnover in South Asian women and it is not well elucidated as to whether Western dwelling South Asian women have different bone resorption levels to that of women from European ethnic backgrounds. This study assessed bone resorption levels in UK dwelling South Asian and Caucasian women as well as evaluating whether seasonal variation in 25-hydroxyvitamin D [25(OH)D] is associated with bone resorption in either ethnic group. Data for seasonal measures of urinary N-telopeptide of collagen (uNTX) and serum 25(OH)D were analysed from n = 373 women (four groups; South Asian postmenopausal n = 44, South Asian premenopausal n = 50, Caucasian postmenopausal n = 144, Caucasian premenopausal n = 135) (mean (± SD) age 48 (14) years; age range 18–79 years) who participated in the longitudinal D-FINES (Diet, Food Intake, Nutrition and Exposure to the Sun in Southern England) cohort study (2006–2007). A mixed between-within subjects ANOVA (n = 192) showed a between subjects effect of the four groups (P < 0.001) on uNTX concentration, but no significant main effect of season (P = 0.163). Bonferroni adjusted Post hoc tests (P ≤ 0.008) suggested that there was no significant difference between the postmenopausal Asian and premenopausal Asian groups. Season specific age-matched-pairs analyses showed that in winter (P = 0.04) and spring (P = 0.007), premenopausal Asian women had a 16 to 20 nmol BCE/mmol Cr higher uNTX than premenopausal Caucasian women. The (amplitude/mesor) ratio (i.e. seasonal change) for 25(OH)D was predictive of uNTX, with estimate (SD) = 0.213 (0.015) and 95% CI (0.182, 0.245; P < 0.001) in a non-linear mixed model (n = 154). This showed that individuals with a higher seasonal change in 25(OH)D, adjusted for overall 25(OH)D concentration, showed increased levels of uNTX. Although the effect size was smaller than for the amplitude/mesor ratio, the mesor for 25(OH)D concentration was also predictive of uNTX, with estimate (SD) = − 0.035 (0.004), and 95% CI (− 0.043, − 0.028; P < 0.001). This study demonstrates higher levels of uNTX in premenopausal South Asian women than would be expected for their age, being greater than same-age Caucasian women, and similar to postmenopausal Asian women. This highlights potentially higher than expected bone resorption levels in premenopausal South Asian women which, if not offset by concurrent increased bone formation, may have future clinical and public health implications which warrant further investigation. Individuals with a larger seasonal change in 25(OH)D concentration showed an increased bone resorption, an association which was larger than that of the 25(OH)D yearly average, suggesting it may be as important clinically to ensure a stable and steady 25(OH)D concentration, as well as one that is high enough to be optimal for bone health