Modeled surface dynamic height in 1964-1984 : an effort to assess how well the low frequencies in the Equatorial Atlantic were sampled in 1982-1984

A wind-forced linear model has been used to produce 21 years (1964--1984) of monthly time series of surface dynamic height in the Equatorial Atlantic. Theclimatological seasonal cycle is substracted, and the statistical characteristics of the residuals are analyzed. An empirical orthogonal function analysis reveals that the most significant pattern has deviations of one sign in the Western Equatorial Atlantic. The anomalies in the last 2 years, 1983 and 1984, are particularly large. The time component of the first empirical orthogonal function peaks in july 1983, changes sign at the end of 1983, and has an extremun of the opposite sign in April 1984. At that time, the zonal slope of dynamic height had reversed with respect to normal along the equator. (D'aprèsrésumé d'auteur

Vertical structure of the seasonal cycle in the Central Equatorial Atlantic ocean : XBT sections from 1980 to 1988

A set of temperature profiles from expendable bathythermographs collected from 1980 to april 1988 along two ship routes transecting the Equatorial Atlantic from 11°N to 11°S is analyzed to infer the vertical structure of the annual variability of the temperature and the currents in the upper ocean. During the average seasonal cycle, the vertical isotherm displacements occur earlier below 300 meters than near the surface at most locations within 4 degrees of the equator. At the equator the amplitude of the displacements does not decrease with depth in the upper 500 meters. This still holds down to 700 meters, but there are less data at these depths. The lead of the deeper isotherm displacements with respect to those in the upper thermocline implies that there is a contribution to the pressure forces from these layers that is not in phase with the contribution of the upper thermocline. This also suggests that the energy source of the seasonal variability is close to the surface. Dynamic height and geostrophic current relative to 400 db are also estimated. A seasonal cycle is found on the subsurface currents, which vary by up to a factor two during the cycle. (Résumé d'auteur

Diurnal Warming Observations with ASIP in the subtropical Northern Atlantic

European Geosciences Union General Assembly 2015 (EGU2015), 12-17 April 2015, Vienna, Austria.-- 1 pageQuantification of air-sea exchange fluxes of energy, moisture, momentum and gases require in situ-measurements of the near-surface layer of the ocean. In the framework of the Salinity Processes in the Upper Ocean Regional Study (SPURS) project, we participated in two cruises to the North Atlantic Salinity Maximum (NASM) region. Observations in the upper ocean are obtained with the Air Sea Interaction Profiler (ASIP), which is an upwardly-rising microstructure instrument designed to study processes in the mixing layer of the ocean. ASIP operates autonomously for up to two days, obtaining undisturbed profiles within the water column from depth to the immediate surface. During the SPURS experiment, ASIP was deployed on several occasions, resulting in a total of over 1000 profiles of the ocean surface boundary layer. ASIP is equipped with microstructure sensors for temperature (FP07), conductivity (SBE07), shear, accurate C-T sensors, a PAR and an oxygen sensor. The high resolution temperature profiles obtained, combined with information on local meteorological variables, allow for an accurate study of the temporal and vertical variability of diurnal warming of the upper ocean boundary layer. Characteristics of the measured diurnal warming at the ocean surface and at specific depth levels are compared to physics-based models of near-surface warming. Mixing rates in the upper ocean are determined from the turbulent dissipation rate, calculated from profiles of the turbulent shear. This information is used to quantify variability between the modeled and observed diurnal warming signalPeer Reviewe

Objective analysis of simulated Equatorial Atlantic ocean data on seasonal time scales

In this study we objectively analyze simulated Equatorial Atlantic ocean data on seasonal time scales using a technique based on optimal interpolation. The purpose is twofold : (1) to estimate the accuracy of the FOCAL/SEQUAL (Programme Français Océan-Climat en Atlantique Equatorial/Seasonal Equatorial Atlantic Response Program) array for mapping large-scale seasonal variations in the depth of the 20° isotherm, and (2) to examine the potential of 20 FOCAL drifting buoys drogued with thermistor chains for enhancing that mapping accuracy. This latter point leads to the development of heuristic model for drifter motion in order to identify the most favorable time and location for buoy deployments. Results are discussed for a number of assumptions about oceanic variability required by both the optimal interpolation procedure and the drifting buoy model. (D'après résumé d'auteur

Surface salinity of the North Atlantic : can we reconstruct its fluctuations over the last one hundred years ?

Surface samples have been collected in the North Atlantic in the past one hundred years for determining the ocean salinity and its temperature. A large share of the data we have used were collected by merchant vessels of weather ships of European countries and to a large extent are listed in reports, in particular in the "Bulletin Hydrographique". We investigate whether these data are relevant for determining low frequency fluctuations of the sea surface salinity. We find many crossing in the 1920s for which salinity is anomalously high compared with the climatology or with other crossings collected on the same ship line. These anomalies are indicative of a contamination of the sample. By examining hydrographic data, reports and recent experience in collectionand storage in sea water, we can attribute these large errors to unclean buckets where salt crystals dissolve into the sample and to breathing of the samples during the storage. Each of these stages contributes in estimating a too large salinity and adds to the scatter of the measurements. (D'après résumé d'auteur

SOOP Network Enhancement Report

Report on the network enhancement project, this will document (a) extension of network coverage to South Atlantic; (b) evaluation of improved EOV carbonate system; and (c) re-assessment of instrumentatio

Stable isotopes in surface waters of the Atlantic Ocean: Indicators of ocean-atmosphere water fluxes and oceanic mixing processes

Publisher's version (útgefin grein)The surface ocean hydrological cycle is explored based on ∼300 new δ18O and δD measurements from surface waters of the Atlantic Ocean and the Mediterranean Sea over the period 2010–2016. Our approach combines these surface observations with salinity (S) and stable isotope measurements of atmospheric water vapor. The distinct regional S‐δ distributions are used to identify different surface water masses and their horizontal advection. Moreover, based on assumptions on the δ‐S characteristics of seawater sources and the isotope composition of the evaporative (δe) and meteoric water (δMW) fluxes, the δ‐S distribution is used to indicate the relative importance of evaporation (E) and meteoric water inputs (MW). Here δe is estimated from the Craig and Gordon's equation using 120 days of measurements of the ambient air above the Atlantic Ocean collected during three cruises. To provide quantitative estimates of the E:MW ratio, we use the box model from Craig and Gordon (1965). This identifies the subtropical gyre as a region where E:MW ∼2 and the tropical ocean as a region were MW:E ∼2. Finally, we show that the δ18O‐δD distribution is better represented by a linear fit than the δ‐S relationship, even in basins governed by different hydrological processes. We interpret the δ18O‐δD distribution considering the kinetic fractionation processes associated with evaporation. In the tropical region where MW exceeds E, the δ18O‐δD distribution identifies the MW inputs from their kinetic signature, whereas in regions where E exceeds MW, the δ18O‐δD distribution traces the humidity at the sea surface.The Picarro equipment was purchased with support from different French institutions, in particular by IPSL, LOCEAN, LMD, and LATMOS. Work during Strasse on R/V Thalassa and Pirata FR24 on R/V Suroit was supported by three LEFE/IMAGO INSU grants (Strasse, Strasse/SPURS, and PIRATA), with additional support for equipment from IPSL and from OSU Ecce Terra. The authors gratefully acknowledge the association “Les Amis du Jeudi et du Dimanche” for the measurements aboard the RARA AVIS. The authors thank the TOSCA‐SMOS program whose founding was used for installing the SBE45 onboard the RaRa Avis Vessel. The Suratlant Project, as well as the data collection from the Toucan, Colibri and Cap San Lorenzo, are supported by SO SSS in France. Data collection onboard Ovide‐2010 (doi:10.3334/CDIAC/OTG.CLIVAR_OVIDE_2010) and Ovide‐2012 (doi:10.3334/CDIAC/OTG.CLIVAR_OVIDE_2012) cruises was supported by LEFE‐INSU. We also acknowledge Philipe Poupon and Cedric Courson for the sampling aboard the sailing boat Fleur Austral, Tara Expéditions for the sampling aboard the sailing boat Tara, CSIC for the sampling aboard the Sarmiento de Gamboa during the Midas Cruise and MOOSE program (ALLENVI‐INSU) for the sampling onboard R/V L'ATALANTE during the MOOSE‐GE2016 cruise (doi:10.17600/16000700). The authors thank the National Power Company of Iceland Landsvirkjun for their contribution to this research. The data are shared with the free Global Seawater Oxygen‐18 database [Schmidt et al., 1999].Peer reviewe