Launching the CTD

Supplementary Research voyage details

This page details currently available opportunities for Supplementary applications on Research and Transit voyages in the 2017-18 and 2018-19 voyage schedules.

Below are brief descriptions of the Research voyages relevant to this call for Supplementary applications, which will enable applicants to assess the suitability of their proposal.

IN2018_V04 - A/Prof Michael Ellwood (Hobart to Hobart)

The East Australian Current (EAC) is a major western boundary current that moves southward along the eastern margin of Australia. This current is climatically and biologically important as it exercises control over heat and nutrient distribution. The EAC is nutrient depleted to the north,  but as it travels south it entrains iron from a variety of sources – including riverine, sediment resuspension, eddies, lateral exchange of shelf waters, frontal jets and atmospheric dust inputs. Thereby evaluating the concentration of dissolved iron. When the EAC reaches its southern  extent, it breaks up to form eddy-like structures that become incorporated into the Subtropical Front (STF). The STF forms the boundary between warmer nutrient depleted subtropical water and cool nutrient-rich Southern Ocean water. The waters southwest of Tasmania are nutrient rich, but depleted in dissolved iron, which is a typical characteristic of High Nutrient Low Chlorophyll (HNLC) regions within the Southern Ocean.

In springtime, large phytoplankton blooms can be seen associated with mingling of nutrient-depleted EAC waters with nutrient-rich, but iron depleted Southern Ocean waters in the vicinity of the STF east of Tasmania. Therefore, changes to the EAC caused by climatic shifts will have implications on elemental cycling, production, and local climate. We will assess the relationships between production and nutrient supply in the modern ocean while simultaneously improving our interpretations of past ocean records from the region.

Specifically, the aims of this voyage are to:

  1. Assess the sources of external iron to the southern EAC;
  2. Compare and contrast the biogeochemistry of EAC waters with HNLC waters located southwest of Tasmania;
  3. Determine the role of ‘new’ (externally sourced iron) versus ‘recycled’ iron in regulating springtime productivity across the STF;
  4. Test the sensitivity of neodymium and thorium isotope sedimentary records to local sedimentary processes

Map of proposed voyage track

Michael Ellwood voyage track

IN2018_V05 – Professor Nathan Bindoff (Hobart to Hobart)

The Antarctic Circumpolar Current (ACC) is a system of eastward flowing jets, standing meanders, and transient eddies that plays a disproportionately large role in climate. Its steeply-sloping density surfaces permits a global-scale overturning circulation that has allowed the ocean to absorb 93% of global warming, 65% of which is taken up in the Southern Ocean, and approximately 26% of anthropogenic carbon dioxide emissions. The ACC is forced at the surface by westerly winds and heat and freshwater fluxes. The Southern Ocean westerlies have been strengthening over the last two decades (by ~20%). Yet the strength of the ACC and the tilt of density surfaces across the current have remained constant. This puzzle is a large gap in our understanding of the ACC response to climate signals, and the ACC’s influence back upon the global circulation and continuing uptake of heat and carbon dioxide by the ocean.

Recent numerical studies emphasize the crucial role played by localized standing meanders that occur at only a handful of sites where the ACC encounters rough topography. They indicate that the ‘brakes’ on the ACC are applied strongly and abruptly in these few locations rather than continuously along the circumpolar ACC. Observations are crucially needed to ground-truth present and future theoretical and numerical modeling developments regarding the ACC.

We will obtain a unique 3-dimensional survey of a standing meander in the ACC, and deliver companion high-resolution simulations, to quantify the processes that slow the ACC. Our observations will extend from the meander-scale processes identified in global models, to the internal wave and turbulence scale that the models do not see, to provide a thorough assessment of the meander-eddy-wave-topography interactions that make the ACC insensitive to increasing wind strength.

Map of proposed voyage track

Nathan Bindoff voyage track

IN2018_V06 – Dr Alan Williams (Hobart to Hobart)

Australia has gazetted an ambitious national network of Commonwealth Marine Reserves that includes the iconic Huon and Tasman Fracture reserves off Tasmania where seamounts (‘undersea mountains’) support unique deep-water coral reefs. These reefs rank among the most bio-diverse globally.

Protection of deep-water coral reefs is a high-priority conservation concern nationally and internationally because deep-water corals are very fragile, easily impacted by human activities including bottom trawling, and are believed to recover very slowly. These corals may also be highly vulnerable to climate change because projected changes in water chemistry could limit the ability of corals to build calcareous skeletons.

Despite these concerns, and Australia’s significant investment in marine conservation, several fundamental ecological issues remain to be evaluated. These include defining the spatial extent of deep-sea coral communities inside and outside the Tasmanian reserves, and evaluating the resilience of the communities to bottom trawling. This information is important to understanding the dynamics of deep-sea communities globally, and for developing and implementing conservation management plans.

Our proposed survey aboard RV Investigator will determine the spatial extents of deep-sea coral communities in and adjacent to the Huon and Tasman Fracture reserves, and quantify changes in the communities by comparing samples taken in 2018 to samples taken, using similar methods, in 2007 and 1997. There will be supplementary sampling on the heavily trawled St. Helens Seamount which was surveyed in 2008, and analysis of comparable data from New Zealand. Remarkably, these are the only two sets of replicated surveys encompassing areas of contrasting conservation status and impact history in the world’s oceans.

Our results will be novel and significant by providing world-first recovery and resilience data to the Australian government and other national and international bodies that will help achieve effective monitoring and management actions to enhance the long-term survival probabilities of deep-sea corals.

Map of proposed voyage track 

Alan Williams 2018-19 voyage track

Updated: 21 April 2017