The circumpolar Subantarctic Zone (SAZ) is a globally significant region of water mass formation and carbon dioxide uptake from the atmosphere. Here we synthesise the results of nine voyages over 8 years to describe the seasonal variation in mixed layer properties in the SAZ south of Australia for comparison with biogeochemical process studies carried out in late summer (March 1998) as part of the SAZ Project. Winter mixing extends to depths greater than 400 m, resulting in the formation of Subantarctic Mode Water. In summer the mixed layer shoals to 75-100 m, depths which are still sufficiently deep that phytoplankton growth may be light limited. Nitrate and phosphate concentrations are reduced in summer( e.g., nitrate decreases from greater than 15 to less than 5/ micro mol kg- 1) but remain well above limiting levels. Silicate in contrast, is low throughout the year (4/micro mol kg- 1 in winter and less than 2 / micro mol kg- 1 in summer). Water mass properties along a north-south hydrographic section in March 1998 suggest that near-surface waters spread from south to north across the Subantarctic Front (SAF), supplying cool, fresh, nutrient-rich water to the SAZ. As a consequence, the properties of the southern SAZ differ from those farther north: the mixed layer in the south is cooler, fresher, deeper, higher in nutrients, and bounded below by a halocline (rather than by a seasonal thermocline, as in the northern SAZ). The contrast between the northern and southern SAZ persists throughout the year, suggesting the cross-front exchange occurs year-round and likely contributes to the differences in seasonal thermal amplitude and algal biomass accumulation seen in satellite images. Density-compensated horizontal gradients of temperature and salinity are common in the mixed layer of the SAZ and the northern SAF, consistent with the hypothesis that the vigour of lateral mixing in the mixed layer is a strong function of the magnitude of the lateral density gradient. CTD Data are available for access via the provided URL. Data from the following voyages of the Aurora Australis were used: 1991-1992 Voyage 1 1992-1993 Voyage 9 1994-1995 Voyage 4 1994-1995 Voyage 7 1995-1996 Voyage 1 1996-1997 Voyage 1 1997-1998 Voyage 6

Data were collected during the 1997-1998 austral summer on voyages by the Aurora Australis and Southern Surveyor. Taken from the abstract of the referenced paper: Oceanographic processes in the subantarctic region contribute crucially to the physical and biogeochemical aspects of the global climate system. To explore and quantify these contributions, the Antarctic Cooperative Research Centre (CRC) organised the SAZ Project, a multidisciplinary, multiship investigation carried out south of Australia in the austral summer of 1997-1998. Here we present a brief overview of the SAZ Project and some of its major results, as detailed in the 16 papers that follow in this special section. The Southern Ocean plays an important role in the global oceanic overturning circulation and its influence on the carbon dioxide contents of the atmosphere. Deep waters upwelled to the surface are rich in nutrients and carbon dioxide. Air-sea interaction modifies the upwelled deep waters to form bottom, intermediate, and mode waters, which transport freshwater, oxygen, and carbon dioxide into the ocean interior. The overall effect on atmospheric carbon dioxide is a balance between outgassing from upwelled deep waters and uptake via both dissolution in newly formed waters (sometimes referred to as the solubility pump) and the transport of photosynthetically formed organic carbon to depth in settling particles (referred to as the biological pump). Determining the variations in the overturning circulation and the associated carbon fluxes in the past and their response to increased anthropogenic emissions of carbon dioxide in the future is essential to a full understanding of the controls on global climate. At present the upwelled nutrients are incompletely used. Low light in deep wind-mixed surface layers, lack of the micronutrient iron, and other factors restrict phtyoplankton production so that Southern Ocean surface waters represent the largest high-nutrient, low chlorophyll (HNLC) region in the world.

Oceanographic processes in the subantarctic region contribute crucially to the physical and biogeochemical aspects of the global climate system. To explore and quantify these contributions, the Antarctic Cooperative Research Centre (CRC) organised the SAZ Project, a multidisciplinary, multiship investigation carried out south of Australia in the austral summer of 1997-1998. Taken from the abstracts of the referenced papers: The development of a semi-automated batch HG-AFS method for the shipboard determination of As(III), As(V),MMA and DMA is described. Procedures in the analytical sequence including addition of NaBH4 to samples, cooling and heating the U-trap used for pre-concentration and separation of the arsines, and logging the AFS output are automated. Overall control of the automated tasks into a logical analytical sequence is achieved using a commercially available data acquisition and control package, workbenchmac(TM). Further modifications required for the method to be adapted to shipboard use, including the use of a hydrogen generator, are also detailed. This method shows a number of advantages over a previously reported manual HG-AFS method including, shorter sample throughput time, increased precision and most significantly, ease of use under shipboard conditions. The semi-automated method was operated on the RSV Aurora Australis during a Southern Ocean voyage in March 1998. Arsenic measurements from a surface transect between 42 and 55 degrees S along 141 degrees 30 minutes E, are presented. Application of the method to more routine laboratory use is also discussed. Distribution of the arsenic species total inorganic arsenic [As(V+III)], arsenite [As(III)], monomethyl arsenic(MMA), andd dimethyl arsenic (DMA) was studied in the Subantarctic Zone (SAZ) of the Southern Ocean, south of Australia, during the austral autumn (March 1998). As (V) was the dominant arsenic species in both vertical profiles and surface waters along the meridional transect 42-55 degrees S, 141 degrees 30' E. It was also the only species observed at depths greater than 600 m. Concentrations of the reduced arsenic species (As(III), MMA, and DMA) were low in these waters compared with other oceanic sites with similar concentrations of chlorophyl a. As(III) concentrations could not be reliably quantified at any sites (less than 0.04 nM). The greatest conversion of As(V) to "biological" species was found at the surface in the Subtropical Convergence Zone(2.5%) and decreased heading southward to 1% in the Polar Front (PF). While the decline in methyl arsenic concentrations was broadly associated with water temperature and measures of biological production, slightly different trends were found in the SAZ and PF. North of the Subantarctic Front (SAF), methyl arsenic concentrations were well correlated with water temperature, while south of the front, no such relation existed. In addition, the ratio DMA/MMA increased south of the SAF, associated with a change in the microalgal community composition. Low water temperature, phosphate replete conditions, and low biological productivity in the Southern Ocean all contribute to the concentrations of biologically produced arsenic species in this region being among the lowest reported for oceanic waters.

Oceanographic measurements were collected aboard Aurora Australis cruise au1121, voyage "Marine Science" (i.e. voyage 2.1) 2010/2011, from 4th January to 6th February 2011. The cruise commenced with a full north to south occupation of the CLIVAR/WOCE meridional repeat section SR3, followed by work around the Antarctic continental margin in the region of the Adelie Depression and the former Mertz Glacier ice tongue. A total of 149 CTD vertical profile stations were taken on the cruise, most to within 15 metres of the bottom. Over 2000 Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients (phosphate, nitrate+nitrite and silicate), oxygen-18, dissolved inorganic carbon (i.e. TCO2), alkalinity, pH, helium, tritium, and biological parameters, using a 24 bottle rosette sampler. Upper water column current profile data were collected by a ship mounted ADCP. Meteorological and water property data were collected by the array of ship's underway sensors. An array of 3 bottom mounted ADCP moorings were deployed near the Adelie Depression, for recovery in the 2012/13 season. Underway data were also collected on this voyage, and are linked to this metadata record at the provided URL. A detailed readme is available as part of the download. Finally, ADCP (Acoustic Doppler Current Profiler) data are also linked, and are in Matlab format.

Oceanographic measurements conducted on voyage 6 of the Aurora Australis of the 2000-2001 season. These data comprise CTD (Conductivity, Temperature and Depth) and ADCP (Acoustic Doppler Current Profiler) data. These data were collected by Mark Rosenberg. This metadata record was completed by AADC staff when the data were discovered bundled with acoustics data during a data cleaning exercise. Basic information about voyage 6: The voyage will complete a range of Marine Science activities off the Mawson Coast, and off the Amery Ice Shelf before calling at Davis to retrieve summer personnel and helicopters prior to returning to Hobart. Science equipment calibration will be undertaken at Mawson. (Marine Science activities were interrupted when the Aurora Australis was required to provide assistance in the Polar Bird's attempt to reach Casey, complete the station resupply and return to open water.) Leader: Dr Graham Hosie Deputy Leader: Mr Andrew McEldowney See the readme files in the downloads for more information.

Pressure data from RBR loggers on the SAZ project - Sub-Antarctic zone mooring study of interannual variability in particulate carbon export. These data have been collected on cruises from 1997 to 2009. A readme file is included which provides further information. See the parent record for further information.

Current meter data from the SAZ project - Sub-Antarctic zone mooring study of interannual variability in particulate carbon export. These data have been collected on cruises from 1997 to 2009. Each folder in the download file contains the data as well as a readme providing further information about data capture and quality for that year. See the parent record for further information.

We report on the late winter oceanography observed beneath Antarctic sea ice offshore from the Sabrina and BANZARE coast of Wilkes Land, East Antarctica (115- 125 E) in September-October 2007 during the Sea Ice Physics and Ecosystem eXperiment (SIPEX) research voyage. A pilot program using specifically designed 'through-ice' Conductivity-Temperature-Depth (CTD) and acoustic Doppler current profiling (ADCP) systems was conducted to opportunistically measure water mass properties and ocean currents during major ice stations. This project involved two independent sub-ice observation platforms: A winch-driven Conductivity-Temperature-Depth system for measuring basic water mass properties and an acoustic Doppler current profiling (ADCP)/GPS system for measuring ocean currents and ice drift. Hereafter these are referred to as the CTD and ADCP systems respectively. The CTD system comprised of an Falmouth Scientific Institute (FSI) CTD instrument, a tripod and over 1000m of polyethylene rope on a winch/drum attached to a metal sled.

Oceanographic measurements were conducted on and around the Antarctic shelf in the vicinity of the Mertz Glacier during the southern summer of 2007/2008, on Aurora Australis voyage au0803, V3 2007/2008. Data were collected as part of the CASO (oceanography) and CEAMARC (fishing) programs. The CASO program included occupation of the southern portion of the SR3 transect, plus additional transects down the slope. A total of (130) CTD vertical profile stations were taken, most to within 15 m of the bottom. Over (1400) Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients, CFCs, dissolved inorganic carbon, alkalinity, oxygen-18, germanium, and biological parameters, using a 24 bottle rosette sampler. Full depth current profiles were collected by a lowered acoustic Doppler profiler (LADCP) attached to the rosette package, while near surface current data were collected by a ship mounted ADCP. Additional CTD profiles were taken at 2 subantarctic sites on the transit south. An array of 4 current meter and thermosalinograph moorings were deployed across a basin outflowing from the Mertz Polynya region.

Taken from the accompanying report: Oceanographic measurements were collected aboard the Aurora Australis on cruise au0806 (voyage 6 2007/2008, 22nd March 2008 to 17th April 2008). This cruise completed the CASO oceanographic program begun on the CEAMARC cruise (au0803, voyage 3 2007/2008), with a full occupation of the SR3 transect between Antarctica and Tasmania. CASO program objectives were: 1. to measure changes in water mass properties and inventories throughout the full ocean depth between Australia and Antarctica along 140oE (the CLIVAR/WOCE repeat section SR3), as part of a multi-national International Polar Year program to obtain a circumpolar snapshot of the Southern Ocean in austral summer 2007-8; 2. to estimate the transport of mass, heat and other properties south of Australia, and to compare results to previous occupations of the SR3 line and other sections in the Australian sector; 3. to deploy moorings near the Adelie Depression (142-145oE) as part of a joint Australia-France-Italy program to monitor changes in the properties and flow of Adelie Land Bottom Water; 4. to identify mechanisms responsible for variability in ocean climate south of Australia. The CASO program (with a full occupation of the SR3 transect) was originally scheduled for a single cruise. The shipping schedule was re-arranged following an unexpected period in drydock, due to a problem with the ship's thrusters, and as a result the CASO program was split over the two cruises. Several of the southern stations occupied on the first cruise au0803 were repeated on the second cruise au0806, to minimise the impact on the data set of the time gap between the cruises. A total of 131 CTD vertical profile stations were taken on au0803, and 73 CTD station were taken on au0806, most to within 20 metres of the bottom. During the 2 cruises, over 2900 Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients (phosphate, nitrate+nitrite and silicate), 18O, CFC's, dissolved inorganic carbon, alkalinity, 14C, dissolved organic carbon, density (i.e. analysis of the effect of water composition on water density), germanium/silica/boron isotopes, trace metals, neodymium, chlorophyll-a, cell counts, pigments, genetic analyses, and other biological parameters, using a 24 bottle rosette sampler. Full depth current profiles were collected by an LADCP attached to the CTD package, while upper water column current profile data were collected by a ship mounted ADCP. Data were also collected by the array of ship's underway sensors. This report describes the processing/calibration of the CTD data, and details the data quality. An offset correction is derived for the underway sea surface temperature and salinity data, by comparison with near surface CTD data. CTD station positions are shown in Figures 1 and 2, while CTD station information is summarised in Table 1. Mooring and drifter deployments/recoveries are summarised in Table 14. Mooring data from the Adelie Depression deployments are discussed in the mooring data reports Rosenberg (unpublished report, 2009) and Meijers (unpublished report, 2009). Further cruise itinerary/summary details can be found in the voyage leader reports (Australian Antarctic Division unpublished reports: Riddle, V3 2007/08 VL report; Rintoul, V6 2007/08 VL report). Hydrochemistry and CFC cruise reports are in Appendix 1 and Appendix 2. Details about the data are available in a readme file and a full report in the download file.