Surface water carbon dioxide in the southwest Indian sector of the Southern Ocean: a highly variable CO2 source/sink region in summer

Measurements of partial pressure of carbon dioxide (pCO₂), total dissolved inorganic carbon (TCO₂), total alkalinity (TA) and chlorophyll a (Chl a) have been made in surface water in the southwestern Indian sector of the Southern Ocean (20–85°E) in the austral summer (INDIVAT V cruise, January-February 1987). Between Antarctica and Africa, pCO₂ distribution was linked to the oceanic frontal zones and Chi a variations. The pCO₂ spatial structure was very close to that explored in summer 1967 in the same region but the pCO₂ differences between the ocean and the atmosphere were smaller in 1987 than 20 years ago. At all latitudes we found strongly contrasting surface pCO₂ characteristics between eastern (around 80°E) and western (around 25°E) regions; C02 sources were mainly in the west and CO₂ sinks in the east. South of 60°S, the contrast could be due to biological activity. Between 60°S and the Antarctic Polar Front, intensification of upwelling might be responsible for the higher _pCO₂ values in the west.     

Facies and tectonic significance of two contrasting Miocene basins in south coastal Turkey

Several Miocene basins are developed on a mosaic of deformed Mesozoic carbonate platforms and ophiolitic units in the Antalya region of south-west Turkey. Two of these, the Manavgat and Köprü basins, show contrasting orientations and stratigraphies. The Manavgat basin is orientated broadly SE-NW and contains a succession of shallow-water reef carbonates overlain by a thick sequence of deeper-water marls. The upper part of the succession consists of sandstones, siltstones and conglomerates, mainly deposited by gravity processes. The stratigraphy of the N-S Köprü basin can be subdivided into a western part, which consists of coarse fan delta-conglomerates with local patch reefs, and an eastern part with thinly bedded sandy turbidites. Tooi marks indicate north to south flow in the north of the basin, but a southeasterly direction in the area of intersection with the Manavgat basin in the south-east. In the light of alternative regional hypotheses, it is thought that early Miocene basin initiation is related to coeval southeastward thrusting of the Mesozoic Lycian Nappes. Flexural loading is inferred to have resulted in block faulting of the foreland and this exploited pre-existing lines of structural weakness, dating from early Mesozoic rifting. mid-Miocene relative sea- level rise may relate to global eustacy, and/or regional tectonic subsidence. Finally, late Miocene renewed coarse clastic input (locally very coarse) and basin infilling reflect tectonic uplift to the north, possibly related to continuing Africa-Eurasia convergence in the region.     

Analyses of fault mechanisms and expansion of southwestern Anatolia since the late Miocene

Neotectonic field studies and detailed analyses of Neogene and Quaternary fault mechanisms in southwestern Anatolia enable us to recognize a succession of compressional and extensional events, and to characterize the direction of corresponding regional stresses. The three most important compressive phases occurred during the Miocene, and a much smaller one near the Plio-Quaternary boundary. The last one or two interrupted a widespread extension of much greater duration and amplitude. The whole tectonic evolution resembles that of the Aegean. The large extension by normal faulting is consistent with a minimum stress along a NNE-SSW average direction. It appears that this direction was N-S during the Pliocene and changed to NE-SW sometime during the Quaternary. This dominant NNE-SSW extension, which began during late Miocene or earliest Pliocene, was related to the development of the southwestern Anatolian graben system.     

Conductivity/salinity/temperature relationship of diluted and concentrated standard seawater

The conductivity ratio of diluted and concentrated standard seawater has been measured very accurately in a salinity range from 0 to42permiland at temperature from -1 to30degC. All the data have been fitted into polynomials which are compared with previous data. The specific conductance of seawater is deduced and a polynomial for the full range of salinity and temperature is proposed. Data presented in this paper have been used, with those of Dauphinee presented in this issue, to elaborate the new "Practical Salinity Scale 1978."     

Development and Intercomparison of Condensed Isoprene Oxidation Mechanisms for Global Atmospheric Modeling

A new condensed isoprene oxidation mechanism forglobal atmospheric modeling (MIM) was derived from ahighly detailed master chemical mechanism (MCM). In abox model intercomparison covering a wide range ofboundary layer conditions the MIM was compared withthe MCM and with five other condensed mechanisms, someof which have already been used in global modelingstudies of nonmethane hydrocarbon chemistry. Theresults of MCM and MIM were generally in goodagreement, but the other tested mechanisms exhibitedsubstantial differences relative to the MCM as well asrelative to each other. Different formation yields,reactivities and degradation pathways of organicnitrates formed in the course of isoprene oxidationwere identified as a major reason for the deviations.The relevance of the box model results for chemistrytransport models is discussed, and the need for avalidated reference mechanism and for an improvedrepresentation of isoprene chemistry in global modelsis pointed out.     

Density of standard seawater solutions at atmospheric pressure

Abstract

This paper gives the results of the density of diluted and concentrated standard seawater which has been measured in a salinity range from 0 to 42 and a temperature from 0 to 30°C. Equations for density of standard seawater (S = 35) vs the temperature and for density of standard seawater solutions vs the temperature and salinity have been fitted.     

Using SARAL/AltiKa to Improve Ka-band Altimeter Measurements for Coastal Zones,Hydrology and Ice: The PEACHI Prototype

Following the successful launch of the SARAL space mission in February 2013, the reliability of the innovative AltiKa altimeter has been demonstrated for deep ocean applications, where Ka-band performances are excellent. With the objective to ensure the complementarity but also the continuity with the altimeter Level-2 products provided in the open ocean, the Prototype for Expertise on AltiKa for Coastal, Hydrology and Ice (PEACHI) project has been set up as an initiative of the French space agency, CNES, to provide a data set of research-grade Level-2 parameters that might be interesting for SARAL secondary objectives on the study of coastal dynamics, inland waters, polar oceans, or continental and sea ices. Thus, the PEACHI prototype has been developed to process and accurately tune dedicated algorithms for the assessment of Ka-band parameters, from the instrument processing to geophysical corrections. As a result, the PEACHI prototype routinely provides end users with new or improved altimeter corrections for scientific applications dedicated to mesoscale monitoring but also synergistic science.     

AltiKa Altimeter: Instrument Description and In Flight Performance

On 25 February 2013, the SARAL satellite was launched from the Indian Sriharikota launch site. The key feature of the altimetric payload has been the selection of Ka-band. Using Ka-band avoids the need for a second frequency to correct for the ionosphere delay and eases the sharing of the antenna by the altimeter and the radiometer. The use of the Ka-band also allows the improvement of the range measurement accuracy in a ratio close to 2 due to the use of a wider bandwidth and to a better pulse to pulse echo decorrelation. Eventually, Ka-band antenna aperture is reduced, which limits the pollution within useful ground footprint. A summary of the results obtained during the in-flight assessment phase is given. All the tracking modes have also been gone through. Eventually, a new high data rate mode, called “HD mode” is implemented on AltiKa and has been used. The performance assessment is excellent: the range measurement accuracy is close to 1 cm for 1s averaging and the Significant Wave Height (SWH) noise is less than 5 cm (for a 2m SWH at 1?). The tracking success is close to 100% over oceans and 96% over all surfaces.     

The concentration of the KCl solution whose conductivity is that of standard seawater (35 ‰) at 15°C

The concentration of the potassium chloride solution (KCI) which has the same conductivity as15degC at P79 standard seawater corrected to35.0000permilhas been evaluated. The variation of the conductivity ratio of KCI solutions to standard seawater (35permil) has been measured between 14.8 and15.2degC for KCI solutions whose concentration varies from 32 to 33 g.kg^-1.     

High rates of geomorphological processes in a tropical area: the Remparts River case study (Réunion Island, Indian Ocean)

Reunion Island is characterized by rapid landscape evolution resulting from its cyclonic tropical climate. However, local active surface processes are not well understood. The relationships between climatic events, large scale landslides and torrential transport of sediment by the rivers remain unclear. The Remparts River is an appropriate area for studying such geomorphological processes, as it deeply incises the active Piton de la Fournaise volcano. In this study, different approaches are used to analyze the morphological evolution of the river from the sediment production areas to the outlet over the last 40 years. Recurrent events of huge mass wasting occur at Mahavel Cliff, upstream of one of the river tributaries, the most recent producing around 50×10⁶ m³ of sediment in 1965. Combined analyses of the sequence of cyclonic events, major mass wasting events and aerial photography interpretation over the last 40 years led to the proposal of a functional model of river system responses to these events. The river system can be divided into three compartments, each affected by three classes of geomorphological events. The sedimentary response (erosion and/or aggradation) of each compartment to a triggering event, such as cyclonic rainfall and/or seasonal rise of water discharge, is controlled both by the magnitude of the climatic event and by the state of the compartment resulting from previous evolution. A set of five aerial photographs and a satellite image showing the evolution of the studied area during the last 40 years are examined in detail in the light of the functional model. Observations confirm a rapid and complex evolution of the river bed (erosion and aggradation), and provide information about the dynamics of the sediment transfer from the production areas to the ocean. Analysis of two distinct topographic datasets bracketing the last major cyclone Dina in 2002 allows the estimation of the river sediment budget resulting from this event. The net volume of aggraded sediments in the river bed is estimated at around 8×10⁶ m³.With no major collapse event recorded at Mahavel Cliff, sediment transfer due to the flood associated with the 3-day cyclone Dina event is responsible for this significant increase in river bed sediment volume. This quantification shows that several million cubic meters of sediment may take only a few years to spread over more than 5 km downstream. The river bed has now reached its highest elevation since the 1965 landslide, with potential consequences for natural hazards in the area of the outlet at the city of Saint-Joseph.