RV Investigator Scientific Highlights

Transcription

1 RV Investigator Scientific Highlights Voyage #: Voyage title: IN2015_V01 IMOS Southern Ocean Time Series automated moorings for climate and carbon cycle studies southwest of Tasmania Mobilisation: Hobart, Friday, 20 March 2015 Depart: 0900, Hobart, Saturday, 21 March 2015 Return: 0900, Hobart, Monday, 30 March 2015 Demobilisation: Hobart, Monday, 30 March 2015 Voyage Manager: Max McGuire Contact details: Chief Scientist: Tom Trull Affiliation: CSIRO O&A Contact details: Co-Principal Investigator: Affiliation: Eric Schulz Bureau of Meteorology Contact details:

2 - 2 - Introduction The Southern Ocean is an important part of the global climate system, soaking up carbon dioxide and heat to moderate the earth s atmosphere. The Southern Ocean Time Series observatory uses a set of three automated mooring to measure these processes under extreme conditions, where they are most intense and least studied. The processes occur on many timescales, from the day-night cycle up to ocean basin decadal oscillations and thus high frequency observations sustained over many years are required. New capability on board RV Investigator in the form of radars, aerosol sampling and towed undulating platforms provides important context and extension of these observations. Contribution to the nation The research improves understanding of the global climate system by focussing on a key region the Southern Ocean. Careful sustained observations over the last decade and into the next increases our knowledge of how the ocean interacts with the atmosphere. Improved understanding is essential to enhance advice to the nation on climate variability affecting us now, develop future scenarios and impact assessments, and to make optimal decisions that will affect the nation s future. The work also directly addresses the issue of how ocean biogeochemistry and productivity respond to ocean dynamics, which is an important input to projecting future biogeochemical and ecosystem states. In addition, enhanced understanding of process occurring in the region related to clouds, ocean mixing, waves and rain will also lead to improved forecasts and warnings issued to the public. As a result of this voyage We have a better understanding of the ocean and atmospheric conditions in the Southern Ocean, spanning clouds, rain and aerosols, air-sea fluxes, ocean chemistry (including carbon) and biology. We have continued to build on the records established up to 17 years ago. We have found the presence of low-level clouds using the radar that are not observed by satellites or present in atmospheric models, and estimated the impact of this omission on the radiation budget, and hence the global climate energy balance to be significant (Fig.1).

3 - 3 - Figure 1: Comparison of RV Investigator cloud radar and solar radiation observations from the SOFS-5 mooring. Note the drop in long wave radiation observed by the mooring when heat trapping ceases in the absence of clouds. We also have observed increases in the cloud condensation nuclei concentrations and the fraction of total particles that were able to act as CCN (CCN/CN ratio) in the presence of the low-level clouds (Fig. 2). Increases in sulfate concentration in afternoon were also observed. While this interpretation is still very preliminary this may be the first data from the Southern Ocean linking cloud and aerosol observations.

4 - 4 - Figure 2. Time series of black carbon (BC), cloud condensation nuclei concentration (CCN), number of particles greater than 10 nm in diameter (CN), ratio of CCN/CN and sulfate concentration (SO4) for 26 March. CCN concentration and CCN/CN ratios increase in the afternoon, coincident with the presence of low level clouds shown in Figure 1. Small peaks in BC at 20:00 may represent contamination from the ship exhaust. (Melita Keywood, CSIRO). We mapped the cross-section of a warm-core eddy using the Triaxus undulated towed body (its temperature distribution is shown in Fig.3). Additional sensors on Triaxus mapped biogeochemical and biological properties, and were supported by the collection of samples from the underway seawater supply to support a range of techniques to characterize the microbial community. Figure 3. The oscillations of Triaxus are shown as black lines, between the ocean surface (top) and bottom of the wind stirred surface mixed layer near 200m depth (bottom). This depth range was mapped every 6 minutes, and shows complete structure where the overlying warm water in the eddy core (at left) mixes with the cold water outside the eddy (at right). Knowledge of how eddies affect vertical structure is rare, yet essential to understanding how eddy dynamics affect stratification (i.e. layering of the surface ocean), which in turn affects air-sea exchange of heat and momentum. (Brett Muir, CSIRO).

5 - 5 - We used Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) for the first time onboard a ship to provide macromolecular characterisation of size fractionated particle samples collected by filtering the underway seawater supply. Size - - terms of macromolecular chemistry, with FTIR spectra clearly separated in PCA scores plots (Fig. 4). Spectral loadings plots (Fig. 4) defined the separation of the scores plot clusters in terms of bands assigned to calcite (~870 and 710 cm -1 ) and silica (~1070 cm -1 fraction was dominated by calcite attributed to a preponderance of cocolithophorids in this fraction, whereas the 20- calcite attributed to a majority of diatoms in that fraction. The 5- contain a mixture of these taxonomic groups. Figure 4. A Principal Components scores plots showing the clustering of FTIR spectra from different size filtered fractions from underway seawater (red < 5 um; blue 5-20 um; green um). B. Loadings plots explaining the clustering in the scores plot in terms of differing calcite and silica levels attributed to the presence or absence of cocolithophorids or diatoms in the respective size fractions (Philip Heraud, Monash University).

6 -6We mapped the seafloor at the SOTS site using enhanced swath mapping capability (Fig.5). Figure 5: Ocean floor as mapped by Investigator at SOTS site (Peter Jansen and Bernadette Heaney, CSIRO), showing volcanic structures which complicate the placement of the moorings and require close coordination of the mooring team and ship personnel.

7 - 7 - We commenced a program of enhanced wave observations with refined data processing and new instruments providing further insight to wave spectrum evolution (Fig.6). This work is expected to improve understanding of rare large freak waves. Figure 6: Time evolving wave spectrum observed on the Pulse mooring during a strong wind period generating new wind waves which coalesce into low frequency swell (provided by Enrique Rapido-Gomes, Swinburne Institute of Technology).

8 - 8 - CSR/ROSCOP Parameter CodeS METEOROLOGY MARINE BIOLOGY/FISHERIES M01 Upper air observations B01 Primary productivity M02 Incident radiation B02 Phytoplankton pigments (eg chlorophyll, fluorescence) M05 Occasional standard measurements B71 Particulate organic matter (inc POC, PON) M06 Routine standard measurements B06 Dissolved organic matter (inc DOC) M71 Atmospheric chemistry B72 Biochemical measurements (eg lipids, amino acids) M90 Other meteorological measurements B73 Sediment traps B08 Phytoplankton PHYSICAL OCEANOGRAPHY B09 Zooplankton H71 Surface measurements underway (T,S) B03 Seston H13 Bathythermograph B10 Neuston H09 Water bottle stations B11 Nekton H10 CTD stations B13 Eggs & larvae H11 Subsurface measurements underway (T,S) B07 Pelagic bacteria/micro-organisms H72 Thermistor chain B16 Benthic bacteria/micro-organisms H16 Transparency (eg transmissometer) B17 Phytobenthos H17 Optics (eg underwater light levels) B18 Zoobenthos H73 Geochemical tracers (eg freons) B25 Birds D01 Current meters B26 Mammals & reptiles D71 Current profiler (eg ADCP) B14 Pelagic fish D03 Currents measured from ship drift B19 Demersal fish D04 GEK B20 Molluscs D05 Surface drifters/drifting buoys B21 Crustaceans D06 Neutrally buoyant floats B28 Acoustic reflection on marine organisms

9 - 9 - D09 Sea level (incl. Bottom pressure & inverted echosounder) B37 Taggings D72 Instrumented wave measurements B64 Gear research D90 Other physical oceanographic measurements B65 Exploratory fishing B90 Other biological/fisheries measurements CHEMICAL OCEANOGRAPHY H21 Oxygen MARINE GEOLOGY/GEOPHYSICS H74 Carbon dioxide G01 Dredge H33 Other dissolved gases G02 Grab H22 Phosphate G03 Core - rock H23 Total - P G04 Core - soft bottom H24 Nitrate G08 Bottom photography H25 Nitrite G71 In-situ seafloor measurement/sampling H75 Total - N G72 Geophysical measurements made at depth H76 Ammonia G73 Single-beam echosounding H26 Silicate G74 Multi-beam echosounding H27 Alkalinity G24 Long/short range side scan sonar H28 PH G75 Single channel seismic reflection H30 Trace elements G76 Multichannel seismic reflection H31 Radioactivity G26 Seismic refraction H32 Isotopes G27 Gravity measurements H90 Other chemical oceanographic measurements G28 Magnetic measurements G90 Other geological/geophysical measurements

10 MARINE CONTAMINANTS/POLLUTION P01 P02 P03 P04 P05 P12 P13 P90 Suspended matter Trace metals Petroleum residues Chlorinated hydrocarbons Other dissolved substances Bottom deposits Contaminants in organisms Other contaminant measurements