Antarctic Bottom Water formation and dynamics in a changing climate
Program 1: Circum Antarctic and East Antarctic
My PhD project focuses on Antarctic Bottom Water (AABW) formation and dynamics in a changing climate. This water mass is a major component of the ocean’s meridional overturning circulation, redistributing heat, salt, nutrients, and carbon globally. AABW is mostly produced in coastal polynyas around the Antarctic continent and spreads northward in the abyssal layer, but most global ocean and climate models are not simulating this process correctly and instead form AABW via open-ocean convection. There are also no long-term observations of AABW formation on the Antarctic shelf due to the challenging environment, especially in winter. I am analysing the formation and export of AABW in the ocean–sea-ice model ACCESS-OM2-01 with a global horizontal resolution of 0.1° where the formation of AABW is accurately represented. In my first PhD project, I focus on the interannual variability of AABW formation and export and its sensitivity to atmospheric forcing and sea ice to advance our understanding of the mechanisms controlling the interannual variability of AABW formation.
The Dynamics of the Antarctic Slope Front
Program 1: Circum Antarctic and East Antarctic / Program 3: Sub-regional and Regional Antarctic Margins
Ellie’s Ph.D. project utilises idealised models of the Antarctic Slope Front regimes to represent the key ocean dynamics of the Antarctic margin. The project aims to understand how topography, in the form of canyons and cavities, as well as wind and buoyancy forcings can influence heat transport onto the Antarctic continental shelf., which has implications on basal melt at the Antarctic Margin. Most geographical sections of the ocean around the Antarctic margin can be classified into the Antarctic Slope Front regimes. Hence, the study of the circulation, variability and forcings in these regimes are relevant to many sections of the Antarctic margin and the research of ACEAS.
Southern Ocean phytoplankton calcification
Program 1: Circum Antarctic and East Antarctic
This project will investigate the relevance of calcifying phytoplankton on contemporary and future carbon cycling in the Great Calcite Belt. It will utilise satellite and BioGeoChemical-Argo (BGC-Argo) profiling float data to map regional imprints of calcifying phytoplankton on nutrient and carbon stoichiometry. It will further use laboratory incubations to assess the influence of calcifying phytoplankton on retention (as opposed to deep sequestration) of carbon and alkalinity in the surface with the goal to generate a mechanistic understanding of retention-versus-export processes. The project will also generate flow cytometric and/or microscopic datasets of phytoplankton communities from the sub-Antarctic during ship voyages to ground-truth characterisations of the phytoplankton community derived from BGC-Argo and satellite data. This project ties into Project 1 of ACEAS - determining the CO2 uptake capacity of the sub-Antarctic Southern Ocean with the use of BGC-Argo and satellite observations .
The Ice-Rock Interface Beneath the Great Ice Sheets of East Antarctica Using Seismic Waveforms
Program 1: Circum Antarctic and East Antarctic / Program 3: Sub-regional and Regional Antarctic Margins
My research works toward modifying and developing a computational workflow to model seismic waves propagating through the ice-bedrock interface in the Antarctic environment. By doing so, I aim to better constrain the sensitivity of these structures and features to seismic signals and therefore help predict the expected data return from seismic surveys within the Antarctic interior. My project particularly focuses on the Aurora Basin and Knox Coast region of East Antarctica, where current geophysical observations are sparse and little is known within the deep subglacial basins. My research output will aim to inform upcoming field campaigns within the Denman-Scott area, optimizing the placement of new passive seismic instruments to monitor cryoseismic signals and map the subsurface structures.
Variability and forcing mechanisms of the Weddell Gyre
Program 1: Circum Antarctic and East Antarctic
I am currently finishing my second year as a PhD student at the Climate Change Research Centre, UNSW. My background is in physical oceanography and my current project is focused on the Weddell Gyre, one of the largest features of the circulation in the Southern Ocean. In particular, I am investigating the gyre’s variability in different timescales, from seasonal to decadal, with the aim of understanding the extent and driving mechanisms for this variability. My main tool for this research is ACCESS-OM2 global ocean/sea ice numerical model. I am also contributing to a collaborative project which explores the sensitivity of Antarctic shelf waters and sea ice to wind amplitude. This project involves researchers from the UNSW, ANU and UTas. My PhD research would contribute to the ACEAS research program, since the Weddell Gyre’s variability, its drivers and timescales, have the potential to influence heat transport towards the Antarctic margin, rate and characteristics of dense shelf water production and sea ice concentration amongst others.
Understanding the drivers of interannual to multidecadal ocean heat content changes
Program 1: Circum Antarctic and East Antarctic
I use the ocean-sea ice model ACCESS-OM2 to investigate how tropical climate variability interacts with the West Antarctic shelf circulation. During El Niño events, warm Circumpolar Deep Water is transported onto the continental shelf, and this leads to increased basal melt of grounded ice shelves. I am also planning to run multidecadal simulations with combined El Niño-Southern Oscillation and Southern Annular Mode (SAM) forcing to investigate their impact on West Antarctica. From previous studies, we know that the response of ice shelves in the Amundsen and Bellingshausen Seas is strongest during El Niño and a positive mode of the SAM.
I am particularly interested in engaging with other researchers in ACEAS’ Program 1 who will improve predictions of how ocean warming and sea level will be affected in the future by changes in Antarctica and the Southern Ocean. My project will contribute to determine how atmospheric changes on the interannual to decadal time scale affects the ocean circulation at the Antarctic margin. My PhD project is computational and learning from researchers who focus on observational data and analysis will give me an important and more broad understanding of Antarctic science today and under a future climate.
How the complexity of continental breakup controls ocean circulation
Program 1: Circum Antarctic and East Antarctic / Program 3: Sub-regional and Regional Antarctic Margins
With continents breaking apart or colliding, some seaways between different major ocean basins would open or close to control global ocean circulation. Especially, the opening of polar seaways like Tasmania gateway and the Drake Passage during the past 30-50 million years not only change polar ocean circulations, but also are proposed to potentially link to the onset or expansion of glaciation in the Antarctic. Previous studies have addressed the impacts of gateway opening on ocean circulation from regional to global scales. These model simulations typically compare a completely closed seaway with an open one to investigate the role of the gateway in triggering the onset of ocean currents such as Antarctic Circumpolar Current and Meridional Overturning Circulation. To test the sensitivity of ocean current pattern to gateway parameters such as depth and latitude relative to wind bands. We will conduct sensitivity tests using eddy-permitting models with paleo-bathymetry to ensure a state-of-the-art representation of ocean dynamics. The results of these tests will have the potential to enable us to re-interpret empirical observations of oceanographic flow through the ocean gateway.
Investigating Southern Indian Ocean Climate Variability using High-Resolution Ice Core Water Isotope Records
Program 1: Circum Antarctic and East Antarctic
My project involves producing and interpreting a high-resolution water isotope record from an East Antarctic ice core – the Mount Brown South ice core, which was drilled in 2017/2018. This ice core record will provide us with a ~1000-year-long, an annually-resolved record of climate from Wilhelm II Land, a region of Antarctic which is currently lacking any long-term, high-resolution paleo-climate records. I am primarily interested in the information we can extract from water isotopes at this site, so part of my research involves improving our quantitative understanding of how water isotopes respond to climate conditions (primarily temperature) at this location. This information will then be used to provide a long-term reconstruction of temperature variability at both the ice core site and in the Southern Indian Ocean.
This work has links to Program 1 of ACEAS – the Circum Antarctic and East Antarctic program. There remain broad questions around long-term accumulation and temperature trends in East Antarctic, and a lack of high-resolution paleo-climate records in this location severely limits our abilities to understand these long-term trends. My work will help to constrain local temperature changes, while others involved in the project work to understand long term accumulation variability.
The Origin and Fate of Subantarctic Mode Water and Antarctic Intermediate Water in the Southern Ocean
Program 1: Circum Antarctic and East Antarctic
I am interested in contributing to the ACEAS research program to continue and hopefully extend the projects described above, in particular, to better understand how Subantarctic Mode Water and Antarctic Intermediate Water absorb and store heat into the Southern Ocean. Specifically, I am interested in contributing to research that improves our understanding of how the increased ocean heat uptake is distributed by basin and across water masses, and the related processes at play, such as vertical heat transport via submesoscale / small mesoscale ocean dynamics. These projects will contribute to the ‘Heat and Circulation (2, 3)’ and ‘Detection and Attribution (4)’of Program 1 at ACEAS.
Non-linear controls on ocean circulation and mixing in marginal ice zones
Program 1: Circum Antarctic and East Antarctic
The overturning circulation of the Southern Ocean is a critical aspect of global climate through its dominant role in air-sea heat and carbon exchange. It has been suggested that non-linear processes control the mixing between deep and surface water to generate intermediate water in the Southern Ocean. In this project I will investigate how non-linear mixing processes influence the water mass properties of the marginal ice zone and how they impact the upwelling of deep waters in the Southern Ocean. I will exploit both in-situ observations and both simple theoretical and numerical models. Fundamental understanding gained will be used in conjunction with global climate models to quantify the sensitivity of this system in a changing climate.
This work is part of project 1, specifically trying to address the role of heat and circulation in the circum and East Antarctic.
Glacier change detection using seismology and machine learning
Program 1: Circum Antarctic and East Antarctic / Program 3: Sub-regional and Regional Antarctic Margins
Water at the ice-bedrock interface is a key control on glacier basal motion and subsequently ice sheet mass balance. However, key hydrological processes affecting this interface can be transient or hidden from view, so difficult to detect through satellite or direct observation. The primary goal of my research is to further develop passive seismic techniques for the continuous monitoring of active glaciers. A focus of the research will subsequently be on those hydrological processes that can both generate seismic signals, and influence ice sheet stability.
To achieve these goals and make passive seismology a viable method for characterising glacial hydrology, a variety of modern and innovative techniques from seismology, computational fluid dynamics, and machine learning will be utilised. This also leaves the potential for developed methodology to be extended to more general problems in environmental seismology. We first aim to model the flow of subglacial water using computational fluid models, such as smoothed particle hydrodynamics, and then use classical seismological methods to model the resultant surface expression. We then aim to use insights from these modelling methods to classify observational data according to the causal mechanism, with unsupervised machine learning playing a key role in this analysis.
This research primarily aligns with the goals of ACEAS Program 1 (Circum Antarctic and East Antarctic), in which Professor Reading is co-lead. It is particularly concerned with the focus areas of Sea Level and Detection and Attribution. The work also has links with Program 3 (Sub-regional and Regional Antarctic Margins). As a part of this work, I am linked with the ‘Sub-ice continent’ working group.
Radiolarian contributions to the Southern Ocean silica cycle and a modern appraisal of palaeo-proxy use in the fossil record
Program 2: Regional East Antarctic and its Provinces
The aims of my PhD project are to expand our knowledge regarding modern Southern Ocean radiolarian assemblages and to use the radiolarian record found in deep sea ocean sediment cores as the primary proxy to reconstruct palaeoceanographic parameters in the Sabrina Coast region, East Antarctica.
I have compiled a surface sediment radiolarian dataset for the Southern Ocean and am using this data to quantify radiolarian diversity and richness and exploring how we can utilise this in future palaeoceanographic work, and categorising modern radiolarian assemblages into biogeographic provinces and trying to determine the taxonomic differences, and environmental factors, responsible for province partitions.
This knowledge will then be applied to the radiolarian record found in sediment cores retrieved from the Sabrina Coast shelf and slope environments to investigate the viability of producing radiolarian-based palaeotemperature estimates from cores so near the Antarctic continent and to reconstruct water mass movement on the Sabrina Coast slope and shelf throughout the Holocene.
Improve the resolution of Antarctic ice sheet mass balance
Program 1: Circum Antarctic and East Antarctic / Program 3: Sub-regional and Regional Antarctic Margins
My research aim is to improve the resolution of ice sheet mass balance estimates in the Antarctic. The project focuses on the gravity method, which estimates mass variation using the measurement from the Gravity Recovery and Climate Experiment missions (GRAEE and GRACE-FO). The GRACE and GRACE-FO missions allow direct measurements of monthly gravity variation induced by changes in ice sheet mass. However, the spatial resolution of this method is not good enough to show the real regional mass change, especially for regions that experience high mass variation or near the coast. To overcome this limitation, I will try to utilise ice height measurement from satellite altimetry, which has a higher spatial resolution, in the gravity method. This project will focus on regions with high mass change, such as East Antarctic. I will also investigate the regional mass variation of the Totten Glacier and Denman region.
These high-resolution mass balance estimates align with programs 1 and 3 of ACEAS, as they allow a better understanding, detection and attribution to improve sea level projection.
Deep Earth Controls on Glacial Isostatic Adjustment in East Antarctica: Probing Remote Worlds using Seismic Signals
Program 1: Circum Antarctic and East Antarctic
Currently, East Antarctica contains a sparse distribution of isolated seismic recording stations, and much of East Antarctica has not been thoroughly explored using seismic signals. This makes it a challenge to constrain the material properties of the deep Earth beneath East Antarctica. Accurate models of glacial isostatic adjustment require knowledge of the structure and properties of the crust and upper mantle. My research aims to develop a new methodology for the use of seismic signals from isolated stations in order to constrain the material properties of the deep Earth beneath East Antarctica, focusing on stochastic inversion techniques. The outputs from this research will help to constrain predictions from models of glacial isostatic adjustment and ultimately improve future sea level projections.
The composition and evolution of diatoms around Antarctica inferred from marine sedimentary ancient DNA
Program 3: Sub-regional and Regional Antarctic Margins
My project focuses on the reconstruction of diatom communities using sedaDNA from Antarctica. Through my study I hope to generate significant new knowledge about the response of Antarctica’s most important marine primary producers to past environmental change, leading to improved predictions about their future adaptation to the ongoing climate change, ultimately guiding ecosystem models and conservation efforts for Antarctica.
Hence, I believe my Ph.D. research aligns well with the activities planned by the Paleo-Reconstructions Working Group within Program 3 (Sub-regional and Regional Antarctic Margin) of ACEAS
Antarctic Krill sedaDNA: Probing ancient Antarctic krill populations
Program 3: Sub-regional and Regional Antarctic Margins
Antarctic krill are a keystone species in the Antarctic marine ecosystem which is being threatened by climate change and commercial fisheries. My research aims to explore the population dynamics of Antarctic krill in the past through the use of sedimentary ancient DNA. This includes their abundance and distribution within the Antarctic marine ecosystem. The ability to study and begin understanding the population dynamics of Antarctic krill to past environmental changes is critical to improving predictions of how they will change in the future and assessing potential impacts on their sustainability. Krill leave no fossil record for microscopic investigation resulting in no paleo-studies which target them as of yet, but I hope to make this a realistic goal with the use of sedimentary ancient DNA.
This project primarily aligns with the Program 3 (Sub-regional and Regional Antarctic Margin) and the activities planned by the Paleo-Reconstructions Working Group.
Tracking human and natural changes in the ocean salinity in the southern hemisphere: evidence for Earth's accelerating water cycle
Program 1: Circum Antarctic and East Antarctic
Ocean salinity is a key state variable of the oceans and reflects the imprint of precipitation and evaporation over the global oceans. Global changes of salinity in the global oceans are significant and widespread and the Southern Ocean has distinctly changes to other regions. The evidence is that these changes are driven by changing melt from Antarctica and from changing rainfall patterns (and evaporation) over the global oceans. These changes in the are likely to be a response to human influence in the climate system. In this project, I will mainly focus on: a) “Understand changes to the atmospheric circulation (including heat and moisture fluxes) across timescales associated with anthropogenic forcing, regional and remote variability. “ and b) “Determine how circulation changes/climate modes and other local processes affect ocean circulation at the Antarctic margin.”
Modelling basal melt in Antarctic ice shelf cavities
Program 1: Circum Antarctic and East Antarctic
My project aims to use both idealised and more realistic ocean models to explore the physics of Antarctic ice shelf-ocean interactions and the ocean circulation in and near ice shelf cavities, which are important for predicting future sea level and climate. I am particularly interested in the implementation of these ice-ocean interactions in the newest generation of ocean and climate models. My project aligns well with the focus of ACEAS Program 1 (Circum Antarctic and East Antarctic) in its aim to quantify heat transport and Antarctic melt rates, as well as ACEAS Program 3 (Sub-regional and Regional Antarctic Margins), in its small-scale process focus which includes ice shelf cavities.
A coupled Earth systems approach ti modelling ice sheet change and its implications
Program 1: Circum Antarctic and East Antarctic
Estimating the ice sheet mass loss over the Antarctic Ice Sheet is a key Earth system interaction governed by global warming. However, ice sheet mass balance estimates are fraught with uncertainty. The primary objective of my project is to address the risks in predicting changes in the total ice sheet mass balance and then examining methodologies to reduce the sources of uncertainty. My thesis will indirectly focus on Antarctica’s impact to global sea level through studies such as understanding the risks associated with estimating the ice sheet mass balance using methods such as satellite altimetry, and how these sources of uncertainty can be reduced in the future.
Broadly speaking, I will investigate the complex interactions between the ice-atmosphere-ocean, including forcings and feedbacks. I will apply computational, geophysical, and interdisciplinary approaches to advance the understanding of these interdependent Earth systems with an emphasis on modelling ice sheets and outlet glaciers. There will be a component to better constrain results from satellite altimeter data with ground-based observations and incorporating insights from the evolution of the firn. I will (i) explore potential avenues for coupling different technologies to bridge the information gap in the spatial and temporal coverage over the AIS, and (ii) address the uncertainty introduced by variations in the firn.
Understanding the circulation dynamics and water mass trends in abyssal Southern Ocean
Program 1: Circum Antarctic and East Antarctic
My first PhD project focuses on the Antarctic Bottom Water pathways and their driving mechanisms in the Australian-Antarctic Basin of the Southern Ocean. Antarctic Bottom Water originates in several areas over the Antarctic shelf and forms a lower limb of the meridional overturning circulation controlling the Earth’s climate. After its formation on the shelf, it overflows the shelfbreak and, due to high density and under the effect of gravity, sinks into the abyssal ocean where it spreads northward and eventually covers more than 50% of the ocean floor.
Despite the importance of the Antarctic Bottom Water for the global climate, there are no long-term observations because of Antarctica's remoteness and harsh conditions. I study Antarctic Bottom Water originated in Eastern Antarctica in the ACCESS-OM2 model with 0.1-degree horizontal resolution aiming to find accurate pathways through which the water enters the abyss and to understand the physical mechanisms controlling them.
Long-term changes of phytoplankton in the Southern Ocean
Program 1: Circum Antarctic and East Antarctic / Program 2: Regional East Antarctic and its Provinces
This project will explore the variation of decadal responses and the dynamics of the Southern Ocean phytoplankton using multi-decadal records of satellite observations and large-scale climate drivers (like El Nino/La Nina). This study will play a crucial role in understanding the long-term changes in the ecosystem of the Southern Ocean. 25-year records of satellite-derived physical parameters (sea-surface temperature, wind speed and sea-surface height) and biological parameters (phytoplankton chlorophyll concentration) will be used to conduct this experiment. In addition to these parameters, outputs of ocean models will also be analysed to assess the temporal signals and relationships using statistical and/or machine learning techniques. The outcomes of this project are expected to be helpful in evaluating the impact of various scenarios of change in the physical environment on future changes in phytoplankton.
The activity is part of programs 1 (Circum Antarctic and East Antarctic) and 2 (Regional East Antarctic and its Provinces) of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS).
Ocean circulation and connectivity around the Antarctic margin
Program 1: Circum Antarctic and East Antarctic
My PhD project focuses on large scale circulation and connectivity around the Antarctic margin. Different regions of the Antarctic shelf are connected via two westward flowing currents. However, the timescales over which these currents connect different regions, and the strength and pathways of this connectivity, remain poorly constrained owing to the challenges associated with observing this largely ice-covered region.
To address this, and improve our understanding of circumpolar connectivity around Antarctica, I use Lagrangian particle tracking in a high-resolution ocean-sea ice model. The findings of this project help to understand the locations and timescales over which anomalies, such as meltwater from the Antarctic Ice Sheet, can be redistributed downstream, feeding into ACEAS Program 1. My second PhD project explores the vulnerability of the Antarctic coastline to non-native marine biota that arrive via rafting ocean objects. Antarctica is generally considered a pristine environment, with much of the marine ecosystem showing high levels of endemism, making it particularly vulnerable to the introduction of non-native species. The extreme environmental conditions in Antarctica, which have traditionally been considered a barrier to the successful establishment of these non-native species, are becoming increasingly more suitable for a variety of non-native biota, warranting an investigation into which regions are, and will be, most vulnerable in the future. Understanding when and where these impacts will first be felt is important for informing monitoring and management practices around the continent. This project ties into ACEAS Programs 1 and 2.
Understanding the mechanism of Southern Ocean deep chlorophyll maxima
Program 1: Circum Antarctic and East Antarctic / Program 2: Regional East Antarctic and its Provinces
Deep chlorophyll maxima (DCMs) are a phenomenon that widely consists in the ocean that the chlorophyll has maximum concentration below the sea surface. A biomass maximum is existing with DCMs simultaneously, affecting the Southern Ocean food-webs and carbon cycle. DCMs are mostly studied in tropical and subtropical ocean, which is mainly influenced by the surface nutrient limitation. The formation of DCMs in the Southern Ocean is different with that in tropical regions. Southern Ocean is such an HNLC area, which is caused by the low iron abundance on the surface water, which could cause DCMs. Additionally, light, temperature and grazing are regarded as the proposed factors impacting the Southern Ocean DCMs. In this project, I will use biogeochemical model to simulate the seasonal variation of chlorophyll distribution in Southern Ocean to determine how DCMs form. Also, I will do some sensitivity tests to show which factor(s) drive the formation of Southern Ocean DCMs and how the Southern Ocean DCMs influence the marine biological production and the global carbon cycle. This project aligns with ACEAS Program 1 and 2, help understanding the drivers of DCMs and the contribution to Southern Ocean productivity and biogeochemical cycles.
