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.

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: In March 1998 we measured iron in the upper water column and conducted iron- and nutrient-enrichment bottle-incubation experiments in the open-ocean Subantarctic region southwest of Tasmania, Australia. In the Subtropical Convergence Zone (~42 degrees S, 142 degrees E), silicic acid concentrations were low (less than 1.5 micro-M) in the upper water column, whereas pronounced vertical gradients in dissolved iron concentration (0.12-0.84 nM) were observed, presumably reflecting the interleaving of Subtropical and Subantarctic waters, and mineral aerosol input. Results of a bottle-incubation experiment performed at this location indicate that phytoplankton growth rates were limited by iron deficiency within the iron-poor layer of the euphotic zone. In the Subantarctic water mass (-46.8 degrees S, 142 degrees E), low concentrations of dissolved iron (0.05-0.11 nM) and silicic acid (less than 1 micro-M) were measured throughout the upper water column, and our experimental results indicate that algal growth was limited by iron deficiency. These observations suggest that availability of dissolved iron is a primary factor limiting phytoplankton growth over much of the Subantarctic Southern Ocean in the late summer and autumn. The importance of resource limitation in controlling bacterial growth in the high-nutrient, low-chlorophyll (HNLC) region of the Southern Ocean was experimentally determined during February and March 1998. Organic- and inorganic-nutrient enrichment experiments were performed between 42 degrees S and 55 degrees S along 141 degrees E. Bacterial abundance, mean cell volume, and [3H]thymidine and [3H]leucine incorporation were measured during 4- to 5-day incubations. Bacterial biomass, production, and rates of growth all responded to organic enrichments in three of the four experiments. These results indicate that bacterial growth was constrained primarily by the availability of dissolved organic matter. Bacterial growth in the subtropical front, subantarctic zone, and subantarctic front responded most favourably to additions of dissolved free amino acids or glucose plus ammonium. Bacterial growth in these regions may be limited by input of both organic matter and reduced nitrogen. Unlike similar experimental results in other HNLC regions (subarctic and equatorial Pacific), growth stimulation of bacteria in the Southern Ocean resulted in significant biomass accumulation, apparently by stimulating bacterial growth in excess of removal processes. Bacterial growth was relatively unchanged by additions of iron alone; however, additions of glucose plus iron resulted in substantial increases in rates of bacterial growth and biomass accumulation. These results imply that bacterial growth efficiency and nitrogen utilisation may be partly constrained by iron availability in the HNLC Southern Ocean. The download file also contains three excel spreadsheets of iron data from the project. The file Sedwick_A9706_Fe_data contains water-column dissolved Fe and total-dissolvable Fe data from cruise A9706, which is presented in Sedwick et al. (1999) and Sedwick et al. (2008). The files Sedwick_A9706_ProcessStn1_Exp_data and Sedwick_A9706_ProcessStn2_Exp_data present data from shipboard experiments conducted during cruise A9706 at Process Stations 1 and 2, respectively, as reported in Sedwick et al. (1999).

This dataset contains chlorophyll a data collected by the Aurora Australis on Voyage 6, 1997-1998 - the SAZ (Subantarctic Zone) cruise. Samples were collected in March of 1998. These data were collected as part of ASAC project 40 (The role of antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms).

This dataset is derived from sediment trap records collected by Thomas Trull as part of the multidisciplinary SAZ Project initiated in 1997 by the Antarctic Cooperative Research Centre (ACE CRC) (Trull et al 2001b). The current submission provides data not included in Wilks et al. (submitted) 'Biogeochemical flux and phytoplankton assemblage variability: A unique year-long sediment trap record in the Australian Sector of the Subantarctic Zone.' This dataset contains three parts: Supplementary Table 1 describes sediment trap deployment information and current speed measured during deployment. Supplementary tables 2a and 2b are raw diatom counts of every species encountered at the site, at every sampling cup. Table 2a contains the 500 m trap depth record, while table 2b is for the 2000 m trap depth record. Supplementary table 3 contains environmental data (chlorophyll-a, photosynthetically active radiation, and sea surface temperature) for each cup record.

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

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 paper: We developed and applied a one-dimensional (z) biophysical model to the Subantarctic Zone (SAZ) and the Polar Frontal Zone (PFZ) to simulate seasonal phosphate export production and resupply. The physical component of our model was capable of reproducing the observed seasonal amplitude of sea surface temperature and mixed layer depth. In the biological component of the model we used incident light, mixed layer depth, phosphate availability, and estimates of phytoplankton biomass from the Sea-viewing Wide Field-of-view Sensor to determine production and tuned the model to reproduce the observed seasonal cycle of phosphate. We carried out a series of sensitivity studies, taking into account uncertainties in both physical fields and biological formulations (including potential influence of iron limitation), which led to several robust conclusions (as represented by the ranges below). The major growing season contributed 66-76% of the annual export production in both regions. The simulated annual export production was significantly higher in the PZF (68-83 mmol P m-2) than in the SAZ (52-61 mmol P m-2) despite the PFZ's having lower seasonal nutrient depletion. The higher export production in the PFZ was due to its greater resupply of phosphate to the upper ocean during the September to March period (27-37 mmol P m-2) relative to that in the SAZ (8-15 mmol P m-2). Hence seasonal nutrient depletion was a better estimate of seasonal export production in the SAZ, as demonstrated by its higher ratio of seasonal depletion/export (64-78%) relative to that in the PFZ (34-47%). In the SAZ, vertical mixing was the dominant mechanism for supplying phosphate to the euphotic zone, whereas in the PFZ, vertical mixing supplied only 37% of the phosphate to the euphotic zone, whereas in the PFZ, vertical mixing supplied only 37% of the phosphate to the euphotic zone and horizontal transport supplied the remaining 63%.

Data were collected during the 1997-1998 austral summer on voyages by the Aurora Australis and Southern Surveyor. 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. Ammonia data were collected by Ros Watson (and provided by Tom Trull), and as of 2012, are unpublished.

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 SAZ project organised by the Antarctic CRC has a continuing program of moored sinking particle trap studies in the Aub-Antarctic and Polar Frontal zones southwest of Tasmania along 140 degrees E. The first deployment obtained weekly or higher resolution samples through the austral summer from September 1997 through February 1998 at three locations: the central Sub-Antarctic Zone (47 degrees S, traps at 1000, 2000 and 3800 m depth), the Sub-Antarctic Front (51 degrees S, 1 trap at 3300 m) and above the Southeast Indian Ridge in the Polar Frontal Zone (54 degrees S, 2 traps at 800 and 1500 m). The particles were analysed for total mass, inorganic carbon, total carbon, nitrogen, silicon, and aluminium. Hence values for organic carbon, biogenic silica, and lithogenics were obtained, and the mass fluxes calculated. This report details the sites, moorings, data from the current meters and sediment traps, and results of analyses performed on the collected sediment trap material. Sediment trap moorings were deployed from September 21, 1997 through February 21, 1998 at three locations south of Australia along 140 degrees E: at -47 degrees S in the central Subantarctic Zone (SAZ) with traps at 1060, 2050, and 3850 m depth, at-51 degrees S in the Subantarctic Front with one trap at 3080m, and at -54 degrees S in the Polar Front Zone(PFZ) with traps at 830 and 1580m. Particle fluxes were high at all the sites (18-32gm-2 yr-1 total mass and 0.5-1.4g organic carbon m-2 yr-1 at ~1000m, assuming minimal flux outside the sampled summer period). These values are similar to other Southern Ocean results and to the median estimated for the global ocean by Lampitt and Antia [1997], and emphasise that the Southern Ocean exports considerable carbon to the deep sea despite its "high-nutrient, low chlorophyll" characteristics. The SAZ site was dominated by carbonate (greater than 50% of total mass) and the PFZ site by biogenic silica (greater than 50% of total mass). Both sites exhibited high export in spring and late summer, with an intervening low flux period in December. For the 153 day collection period, particulate organic carbon export was somewhat higher in all the traps in the SAZ (range 0.57-0.84 gC m -L) than in the PFZ (range 0.31-0.53), with an intermediate value observed at the SAF (0.60). The fraction of surface organic carbon export (estimated from seasonal nutrient depletion, Lourey and Trull [2001]) reaching 1000 m was indistinguishable in the SAZ and PFZ, despite different algal communities.

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.

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.