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|Title:||Atmospheric underway measurements|
|Investigator(s):|| Melita Keywood
CSIRO Oceans & Atmosphere - Aspendale [details]
|Description:||The scientific objective of this work is to investigate the chemical composition,size distribution, optical properties and cloud nucleating properties of marine aerosol over the southern hemisphere with the aim of quantifying regional contributions of aerosols to radiative forcing. There is currently very large uncertainty associated with the direct, semi-direct and indirect effect of aerosols on radiative forcing. A key feature in this regard is the influence on cloud properties of cloud condensation nuclei (CCN), the very small atmospheric aerosol particles necessary for the nucleation of every single cloud droplet. A recent analysis of the 35-year CCN concentration record at Cape challenges the current accepted wisdom of the role of dimethyl sulfide (DMS) on CCN formation over the Southern Ocean. In particular, it appears that DMS oxidation is only significant during the summer months at Cape Grim, and in fact other sources and processes dominate throughout the rest of the year (Gras pers com). That other sources and processes may be significant in CCN production and modulation has also recently been suggested in a review of the CLAW hypothesis. The identity of these sources remains an open question.|
List of surveys that this project was on.
Use [details] link to view survey details (map, reports, metadata etc) including links to download data.
|Simon Williams||RV Investigator research voyage in2016_t01. Titled "Continuity of Australian terranes into Zealandia: towards a geological map of the east Gondwana margin." This is an extract from the Voyage Objectives in the Voyage Plan. We plan 4-6 dredges on the Fairway Ridge and Sandy Island area. The specific locations of potential dredge sites are shown on the voyage plan image and are tied to a confidential seismic reflection profile and/or swath bathymetry data. As we have access to high-resolution swath data from the area from the Geological Survey of New Caledonia, there is no necessity to plan a detailed swath survey for each dredge site. Swath bathymetry and ocean-bottom profiles (continuous collection) We will continuously collect bathymetric data and the North Loyalty Basin will be crossed during the transit voyage, thus requiring no additional time to collect this important swath profile. Gravity (continuous collection) We will continuously collect gravity data. There is no deviation necessary to obtain gravity measurements over the northwestern part of the Fairway Ridge as we will be crossing this area as part of the dredging component of the survey. CTD, hydrocast and bio-optical cast We will take two daily CTD profiles and hydrocast water samples to 500m to characterise the water at time of deployment for pigment, nutrient, dissolved oxygen, dissolved inorganic carbon and total alkalinity concentrations (up to 25 stations over the whole voyage). For this we will require the 36-bottle CTD rosette. Additional sensors to be included on the CTD frame include chlorophyll and CDOM fluorometers, absorption and backscattering meter, beam transmissometer, dissolved oxygen, deep SUNA and SeaFET pH. A Satlantic radiometer will be deployed separately at each station to a depth of 200m. We will be able to provide sensors that are not available through the MNF equipment pool (i.e. Satlantic SeaFET pH, Satlantic radiometer, Wetlabs acs and bb9, Hobilabs Hydroscat-6). Water samples will be filtered or chemically fixed on board according to standard operating procedures. We anticipate each deployment station taking 1.5 hours, with deployments taking place at the same time each morning and afternoon (nominally 0930 and 1400 hours), when not conflicting with dredge operations. Robotic Profiling Floats and bio-optics CSIRO will provide floats equipped with CTD and bio-optical sensors to measure a range of parameters: T, S, dissolved oxygen, chl and CDOM fluorescence, backscattering (4 wavelengths), beam attenuation, upwelling radiance and downwelling irradiance (4 wavelengths). Floats will be deployed at stations within Australian waters along the ship's route of transit (estimate 155E and 160E). Deployment of the floats can be undertaken from the A-frame off the rear deck or by two people using a rope and manhandling the float over the stern. Once deployed, the floats will descend to depth and start their pre-programmed cycle of profiling and data collection, with data transmitted via Iridium satellites. During each deployment we will also take a CTD profile and water samples to 1000m to characterise the water at time of deployment for pigment, nutrient, dissolved oxygen, dissolved inorganic carbon and total alkalinity concentrations. Additional sensors to be included on the CTD include chlorophyll and CDOM fluorometers, backscattering meter and/or beam transmissometer, dissolved oxygen, deep SUNA and possibly SeaFET pH. We will seek to provide sensors that are not available through the MNF equipment pool (e.g. pH). Water samples will be filtered or chemically fixed on board according to standard operating procedures. We anticipate each deployment station taking 2-4 hours. Additional CTD and bio-optical casts will be taken twice per day (morning and afternoon, nominally 9.30am and 2pm) for bio-optical and biogeochemical sampling around the time of satellite overpasses. Full details available in the Voyage Plan.|