Weddell Sea
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This research addressed a feasibility study for a remote monitoring system based on acoustic tomography to be used in antarctic regions. The analysis of data collected during PNRA oceanographic campaigns provided the environmental scenarios and the oceanographic processes to be successfully monitored by means of acoustic tomography and the appropriate information and data to initialize the tomographic processor. The case studies regarded High Salinity Shelf Water formation process in Terra Nova Bay polynya. The simplified but realistic environmental scenario considered a 1000 m deep area with a flat bottom. The dense water formation area was defined by a strong vertical salinity gradient in the surface, while in the areas outside, temperature and salinity were considered constant in depth leading to an almost linear increasing sound speed profile. At this stage of study, the possible presence of ice layer covering the area is not expected to have any significant effect on the propagation prediction, so it was not considered. Simulations were carried out with a beam model (Bellhop) which is well suited for active sonar modelling and ocean acoustic tomography in a range dependent environment. Each simulation involves the use of an acoustic source and a receiving station (tomographic pair) consisting of a vertical array of hydrophones. By measuring the travel time relative to different scenarios, the analysis aimed at understanding if the detection of the oceanographic phenomenon is feasible. In particular, the study aimed at determining the best compromise between acoustic frequencies, sensors number and geometrical configuration, in order to achieve the desired spatial-temporal resolution useful to detect the presence of dense water masses. An acoustic system configuration consisting of an acoustic source transmitting a pulse with a carrier frequency of 10 kHz, and of a receiving array made of 6 hydrophones resulted to be appropriate, while the minimum size of detectable Dense Water Mass is 0.5 km. In particular, the conducted sensitivity study evidences that the measure of travel time of acoustic rays can be successfully exploited to detect the presence of a dense water mass in a polynya area Acoustic tomography thus provides “images” of wide areas in the inner ocean for long periods and with an high temporal resolution; in addition it permits to reconstruct the sound speed field even in the upper layers where direct measurements cannot be performed as instruments are at risk of damage. It can then be consider a powerful mean of observation that well integrates conventional in situ measurements. Preliminar investigation on the applicability of this methodology in Terranova Bay polynya demonstrated that it is able to resolve the vertical structure of water column with a good precision.
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The UV spectral measurement at ground it’s a diffuse method to determine the stratospheric ozone content. The main objective of the project was the assembling of the UV filter radiometer (named F-RAD) for the measurements of the Sun global irradiance at the Mario Zucchelli Station (MZS), Terranova Bay, Antarctica. The main parts of the instruments are: the entrance radiation optical system, the filters selecting the wavelength of interest and the control system, hardware and software, governing all the measurement steps. The main requirements were: time resolution of one minute and spectral resolution less than 1 nm. The researchers of the project have been participated at two Antarctica campaign, the XXI campaign, 2005, and the XXV campaign, 2009. - XXI Campaign: the radiometer was tested in the Antarctica environment in order to check the reliability of the different components and the optical stability of the filters. - XXV Campaign: the radiometer F-RAD was definitively placed on the roof of one of the MZS building and connected with the Local Area Network of the base. the UV data were daily downloaded in Italy. The spectral UV data acquired with high time resolution, each wavelength was measured 1430 time per day and high spectral resolution, the filters have a FWHM of 0.5- 0.8 nm. F-RAD was placed in Antarctica in November 2009 and works properly, the different parameters are checked daily.
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Exploratory study for the development of technologies required for biological, geological and physical-chemical entry and sampling in subglacial lakes under high contamination-free conditions. The proposed activity is part of an international initiative, promoted and sponsored by SCAR and COMNAP in which Italy is also represented. The scientific objective is the development of miniaturized technologies for the execution of chemical-physical-biological measurements and of remoting technologies for the transport of instrumentation to the operational site, possibly enabling "in situ" sampling and material recovery operations.
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Collection of 451 temperature profiles with XBT and 35 profiles of temperature and salinity with XCTD probes in the Drake Strait, the Weddell Sea and between the northern tip of the Antarctica Paeninsula and the Orcadas Islands, to study of the variability of the Mixed Layer and the estimate of the heat content on the first 700 m of the water column, and the large scale representation of the surace and subsurface structure of the ACC. Three oceanographic cruises were performed on board of the Argentinean ice breaker “Almirante Irizar” in the three austral winters 2004-2005, 2005-2006 e 2006-2007. Data are acquired from the 7th of february and the sond were launched with a resolution of 20' of latitude to 70° ad 15' for higher latitudes, to better define the thermal southern front.
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The main goal of our proposal is to characterize the surface radiative budget as well as cloudiness which features at the Argentine Bases Marambio and Belgrano II during the YOPP-SH Special Observing Period (SOP) as well as the YOPP Consolidation Phase. Specific objectives to secure our main goal during the SOP will be: 1 - develop a compact Radiation Measurement UNIT (RMU) robust enough to allow continuous measurements in harsh environment through which to make shortwave, longwave observations as well as to record status of the sky. 2 - secure UV measurements at both stations. 3 - develop specific tools to analyse on a daily basis (weakly for clouds) collected data and extract parameters of interest. For radiation these will include QA/QC SW and LW downwelling and upwelling fluxes, diffuse and direct components of solar radiation, UV spectral flux and doses. For clouds these will include, on a continuous base, cloud fraction derived both from radiometric measurement and sky camera observations, cloud type and cloud effect on SW radiation. In addition cloud base (or cloud ceiling) will be obtained by routine observations performed at the two stations. From UV measurements columnar ozone content will be also derived. Moving forward to YOPP consolidation phase, we plan to: 1 - extend dataset and its analysis, start to collect information on seasonal and inter-annual variability, determine Cloud radiative Forcing (CRF) 2 - perform extensive comparison between automatic and visual cloudiness observation methods. They being very useful to better understand quality and value of historical datasets at the two stationsù 3 - make comparison with cloudiness regime of Ross Sea and Antarctic Plateau. Make similar comparison for UV fluxes in the Peninsula and at Concordia.