OCEANOGRAPHY / SEA-ICE
Chair: Hanne Nielsen
Adam J Campbell, University of Otago, New Zealand
Abstract: The recent variability in thickness and velocity of the Ross Ice Shelf can be attributed to some mixture of external forcings, internal variability. Change in mass balance, both above and below the ice shelf, are sources of external. With changes in the position to of the Antarctica Circumpolar Current, subglacial melting is likely an external forcing to have significantly changed recently. However, the Ross Ice Shelf is experiences internal variability in form of long-lived transient adjustments to boundary conditions. Changes in icestream input to the ice shelf and iceberg calving can both produce transient thickness and velocity adjustments that persist for decades to centuries.
Here I demonstrate the scale of thickness and velocity transients that are induced by changes in boundary conditions. I test several test case scenarios: the grounding and ungrounding of Steershead ice rise, ice stream variability and tabular iceberg calving. The pattern and magnitude of these transient signals are compared to modern observations.
BIOLOGICAL - MARINE / FRESHWATER / TERRESTRIAL
Jan Jansen, University of Tasmania, Institute for Marine and Antarctic Studies, Australia
Abstract: More than 90% of the world’s oceans occur beneath 200m depth at which light attenuates to such an extent that no photosynthesis occurs. The diversity of life on the seafloor beneath this depth must derive energy from alternative sources such as food raining from the surface, a link often referred to as benthic-pelagic coupling. However, the nature and strength of benthic-pelagic coupling, and its influence on the structure and diversity of seafloor communities remains unclear, especially in Antarctica where ecological data are sparse. Here I present results from a novel approach combining physical models with a statistical framework that show benthic-pelagic coupling in East Antarctica depends on physical processes and varies considerably depending on the types of benthic organisms considered.
We used a particle tracking model, informed by remotely sensed surface productivity and combined with a regional oceanographic model to quantify the flux of food to the seafloor in the George V shelf area in East Antarctica. We optimised the particle tracking model-parameters by the statistical fit of the resulting particle distribution to data from sediment cores revealing spatial patterns food-abundance change little during the fast (200m/day) sinking to the seafloor. Fluctuating seabed currents however, are crucial in the redistribution of particles on the seafloor. Analysing data from towed still cameras we found the abundance and diversity of benthic filter feeders, but not other benthic groups to correlate strongly with the estimate of horizontal flux of food particles above the seafloor, enabling spatial predictions of seafloor biodiversity over vast regions of Antarctica.
Lavenia Ratnarajah, Institute for Marine and Antarctic Studies, Antarctic Climate and Ecosystems Cooperative Research Centre, Australia
Abstract: Iron limits primary productivity in large areas of the Southern Ocean. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but evidence on their contribution is scarce. We analysed the concentration of iron in baleen whale faeces and muscle. Iron concentrations in whale faecal matter were almost 10 million times higher than typical Southern Ocean High Nutrient Low Chlorophyll seawater concentrations. Iron to carbon ratios was also higher in whale faeces compared to muscle indicating that whales are concentrating carbon and defecating iron.
We developed an exploratory model to examine potential contribution of blue, fin and humpback whales to the Southern Ocean iron cycle to explore the effect of the recovery of great whales to historical levels. Our results suggest that pre-exploitation populations of blue whales and, to a lesser extent fin and humpback whales, could have contributed to the more effective recycling of iron in surface waters, resulting in enhanced phytoplankton production. This enhanced primary productivity is estimated to be: 8.3 x 10-5 to 15 g C m-2 yr-1 (blue whales), 7 x 10-5 to 9 g C m-2 yr-1 (fin whales), and 10-5 to 1.7 g C m-2 yr-1 (humpback whales). To put these into perspective, current estimates of primary production in the Southern Ocean from remotely sensed ocean colour are in the order of 57 g C m-2 yr-1 (south of 50°). The high degree of uncertainty around the magnitude of these increases in primary productivity is mainly due to our limited quantitative understanding of key biogeochemical processes including iron content in krill, krill consumption rates by whales, persistence of iron in the photic zone, bioavailability of retained iron, and carbon-to-iron ratio of phytoplankton. We are actively working on addressing these unknowns.
Delphi Ward1,2,3, Jessica Melbourne-Thomas2,3, Simon Wotherspoon1,3, Craig Johnson1, Mark Hindell1,2
1 Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia
2 Antarctic Climate & Ecosystem Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
3 Australian Antarctic Division, Department of the Environment, 203 Channel Highway, Kingston, Tasmania 7050, Australia
Abstract: In recent decades, a number of marine ecosystems have undergone enormous changes without warning. The structure and dynamics of these ecosystems changed to such a degree that there was a significant reduction in the biomass of fish available for many important fisheries. This sudden flip from one stable state to another (called a regime shift) is of particular concern because they can be very difficult to reverse, difficult to detect and even more difficult to predict, particularly in data-poor ecosystems such as the Southern Ocean. Failure to recognise such changes and continuing to manage the new ecosystem regime according the dynamics of the previous regime could result in stabilisation of the new, less desirable regime and potentially further deterioration of the ecosystem state. It is therefore essential that we are able to reliably detect whether an ecosystem has undergone a regime shift. Current methods for detecting ecological regime shifts require multiple, high-resolution time series data, or high-resolution, 2D species occurrence data. This data requirement is prohibitive for many ecosystems, especially remote systems such as Southern Ocean ecosystems. To address this gap, we have developed a method for detecting regime shifts from transect data (a more readily available data type for many ecosystems), with the aim of applying it to the Southern Ocean Continuous Plankton Recorder dataset. Our method is an adaptation of existing methods for determining the Characteristic Length Scale of an ecosystem. Changes in this length scale indicate whether the structure of the system has changed. In this talk we first describe this method, and then present insights gained through the application of the method to model systems, and to a coral reef test dataset.
Théo Le Dantec, Université de Toulouse: UPS, INP, EcoLab (Laboratoire Ecologie fonctionnelle et Environnement), France
Abstract: My PhD project aims to better understand the carbon cycle of arctic regions in the context of climate change. We are focusing on the freshwater compartment and the link between terrestrial and aquatic ecosystems. My field work is located near the river mouth of the Yenisey, one of the biggest arctic rivers. To get insights into dissolved organic matter quantity, quality and temporal variations we are sampling river water throughout the year, with a special effort over the spring flood period, which is the time where the major part of the export of carbon occurs. Thanks to various analytical technics ranging from optical properties of organic matter to isotopic and molecular analysis we are tracking the origine of organic matter, its degradation state and potential lability. This information may help to understand the fate of DOM in riverine systems, processes occurring in the watershed, better quantify exports to the arctic ocean, identify sensitive ecosystem and potential feed back to climate change. Participating to the APECS online conference i would like to share about my field experiences in the arctic (Specifically I will be working on the 2016 spring flood sampling by the time of the session) and exchange about analytical approaches to get into DOM complexity with the scientific community.
CULTURAL / HISTORICAL / POLICY / EDUCATION
Miranda Nieboer, University of Tasmania (Humanities) / IMAS, Australia
Abstract: Antarctica is the only continent without indigenous people and has therefore no long-standing tradition of habitation. The interior spaces in the first built structures in Antarctica served primarily as life support systems. Nowadays the interiors of the stations continue to offer humans an opportunity for survival in the Antarctic environment. However, the significance of these interiors reaches beyond their role as pure physical shelter.
Historically the meaning of the word interior has transformed through its application to different spatial scales. The definition of interior has variously designated personal subjectivity, territorial space belonging to a nation and the inside of a building. The interior as idea and as physical space is constructed in both representation and spatial practice. For this reason my research on Antarctic interiors includes case studies on both physical and imaginative interiors.
The Antarctic environment and the multi-scalar definitions of the word ‘interior’ that have ranged from the geopolitical to the individual are the starting points for my study. My research objective is to develop an understanding of how the spatial concept of interior within the Antarctic context is constructed on different scales. I combine interpretive studies of Antarctic (non) fiction narratives and art focused on interior(ity) with visual analysis of Antarctic interior territory and interiors.
For each scale, I select three case studies focussing on:
- the horizontality of the ice plain
- the verticality of the ice mass
- imaginative Antarctic interior space
The case studies are:
- Continent: Mapping / Drilling / The Hollow Earth
- Stations: The Dome / Byrd’s Hut / The Thing
- Interiority: Whiteout / Vertigo / The Antarctic Mind
With this partition I aim to develop an understanding of the relationships of Antarctic interiors within a particular scale and through the different scales.
Hanne Nielsen, University of Tasmania, Australia
Abstract: In 1933 Admiral Richard E. Byrd’s second expedition set sail for Antarctica, ready to make “dairy history.” He took with him three Golden Guernsey cows, “the first cows ever to venture into the frozen wastes of the South Pole Region,” a surge milking machine, ten tons of Larro Dairy Feed, and the curiosity of the American public. The three cows, known as “Klondike Gay Nira”, “Deerfoot Guernsey Maid,” and “Foremost Southern Girl,” were about to become front and centre of a tale of endorsements, nutrition, and animal celebrity, broadcast back home from the ends of the earth.
The story of Byrd’s South Pole Dairy does far more than reveal a lesser-known side-track in Antarctic history. Instead, it highlights the issues sponsorship, media, publicity, and colonisation, illustrating the ways Antarctica has been used as a tool in a commercial context. Thanks to advertising and media endorsements, the cows were used to raise the profile of both the products used on the Byrd expedition, and of the expedition itself. Meanwhile, the presence of such domesticated animals on an icy no-man’s land reinforced Byrd’s desire to stake a claim in Antarctica for his homeland. These Antarctic cows may have appeared as little more than a footnote in Antarctic history, but their story is revealing of the commercial and nationalist context of Byrd’s second Antarctic expedition. The Golden Guernseys are not just cows, but rather the entry point into a stable of icy stories about our past.
 Admiral Byrd takes Larro to the South Pole. 2
 Admiral Byrd takes Larro to the South Pole. 2
 Polar Guernseys Withstand First Test. 2. 4 November 1933.
Chair: Hanne Nielsen