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Beschreibung: Observations made near the Celtic Sea shelf edge are used to investigate the interaction between wind generated near-inertial oscillations and the semi-diurnal internal tide. Linear, baroclinic energy fluxes within the near-inertial ( f ) and semi-diurnal (M 2 ) wave bands are calculated from measurements of velocity and density structure at two moorings located 40 km from the internal tidal generation zone. Over the two week deployment period the semi-diurnal tide drove 28-48 W m -1 of energy directly on-shelf. Little spring-neap variability could be detected. Horizontal near-inertial energy fluxes were an order of magnitude weaker, but non-linear interaction between the vertical shear of inertial oscillations and the vertical velocity associated with the semi-diurnal internal tide led to a 25-43% increase in positive on-shelf energy flux. The phase relationship between f and M 2 determines whether this non-linear interaction enhances or dampens the linear tidal component of the flux, and introduces a 2-day counter clockwise beating to the energy transport. Two very clear contrasting regimes of (a) tidally and (b) inertially driven shear and energy flux are captured in the observations.

Print ISSN: 0148-0227

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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A Cenozoic uplift history of Mexico and its surroundings from longitudinal river profiles (2014)

Simon N. Stephenson, Gareth G. Roberts, Mark J. Hoggard, Alexander C. Whittaker

Wiley

In: Geochemistry Geophysics Geosystems (G3)

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Publikationsdatum: 2014-11-18

Beschreibung: Geodynamic models of mantle convection predict that Mexico and western North America share a history of dynamic support. We calculate admittance between gravity and topography, which indicates that the elastic thickness of the plate in Mexico is 11 km and in western North America it is 12 km. Admittance at wavelengths 〉 500 km in these regions suggests that topography is partly supported by sub-crustal processes. These results corroborate estimates of residual topography from isostatic calculations and suggest that the amount of North American topography supported by the mantle may exceed 1 km. The Cenozoic history of magmatism, sedimentary flux, thermochronometric denudation estimates and uplifted marine terraces imply that North American lithosphere was uplifted and eroded during the last 30 Ma. We jointly invert 533 Mexican and North American longitudinal river profiles to reconstruct a continent-scale rock uplift rate history. Uplift rate is permitted to vary in space and time. Erosional parameters are calibrated using incision rate data in southwest Mexico and the Colorado Plateau. Calculated rock uplift rates were 0.15–0.2 mm/yr between 25–10 Ma. Central Mexico experienced the highest uplift rates. Central and southern Mexico continued to uplift at 0.1 mm/yr until recent times. This uplift history is corroborated by independent constraints. We predict clastic flux to the Gulf of Mexico and compare it to independent estimates. We tentatively suggest that the loop between uplift, erosion and deposition can be closed here. Mexico's staged uplift history suggests that its dynamic support has changed during the last 30 Ma. This article is protected by copyright. All rights reserved.

Digitale ISSN: 1525-2027

Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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Changes in extreme temperature and precipitation in the Caribbean region, 1961–2010 (2014)

Tannecia S. Stephenson, Lucie A. Vincent, Theodore Allen, Cedric J. Van Meerbeeck, Natalie McLean, Thomas C. Peterson, Michael A. Taylor, Arlene P. Aaron-Morrison, Thomas Auguste, Didier Bernard, Joffrey R. I. Boekhoudt, Rosalind C. Blenman, George C. Braithwaite, Glenroy Brown, Mary Butler, Catherine J. M. Cumberbatch, Sheryl Etienne-Leblanc, Dale E. Lake, Delver E. Martin, Joan L. McDonald, Maria Ozoria Zaruela, Avalon O. Porter, Mayra Santana Ramirez, Gerard A. Tamar, Bridget A. Roberts, Sukarni Sallons Mitro, Adrian Shaw, Jacqueline M. Spence, Amos Winter, Adrian R. Trotman

Wiley

In: International Journal of Climatology

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Publikationsdatum: 2014-01-14

Beschreibung: ABSTRACT A workshop was held at the University of the West Indies, Jamaica, in May 2012 to build capacity in climate data rescue and to enhance knowledge about climate change in the Caribbean region. Scientists brought their daily observational surface temperature and precipitation data from weather stations for an assessment of quality and homogeneity and for the calculation of climate indices helpful for studying climate change in their region. This study presents the trends in daily and extreme temperature and precipitation indices in the Caribbean region for records spanning the 1961–2010 and 1986–2010 intervals. Overall, the results show a warming of the surface air temperature at land stations. In general, the indices based on minimum temperature show stronger warming trends than indices calculated from maximum temperature. The frequency of warm days, warm nights and extreme high temperatures has increased while fewer cool days, cool nights and extreme low temperatures were found for both periods. Changes in precipitation indices are less consistent and the trends are generally weak. Small positive trends were found in annual total precipitation, daily intensity, maximum number of consecutive dry days and heavy rainfall events particularly during the period 1986–2010. Correlations between indices and the Atlantic multidecadal oscillation (AMO) index suggest that temperature variability and, to a lesser extent, precipitation extremes are related to the AMO signal of the North Atlantic surface sea temperatures: stronger associations are found in August and September for the temperature indices and in June and October for some of the precipitation indices.

Print ISSN: 0899-8418

Digitale ISSN: 1097-0088

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley

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