Research and impacts
2019-2025

Microbes brightening clouds

The Southern Ocean, occupying around one-fifth of the surface area of the global ocean, plays a pivotal role in regulating Earth’s climate. Our work is highlighting the significant impact of microscopic life in surface waters on atmospheric processes – in particular, the contribution of sulfur gases made by phytoplankton and bacteria to creating aerosol particles that seed clouds.

Dimethyl sulfide (DMS) and methanethiol (MeSH) are two biologically-produced oceanic gases that are key predecessors to climate-cooling aerosols. DMS is the predominant sulfur gas and well known for its role in aerosol and cloud formation. However, the influence of MeSH remains less understood, even though our research collaborations show that MeSH comprises a significant proportion of volatile sulfur from measurements over the Southern Ocean.

To date, there are very few published measurements of MeSH over the Southern Ocean, in both seawater and atmosphere. Now with six months of sampling at Kennaook/Cape Grim in Tasmania and from the 60-day MISO voyage across the Southern Ocean and along the Antarctic coast, we have strong evidence that MeSH is a non-negligible and potentially crucial contributor to the sulfur budget and cloud formation over the Southern Ocean.

With information like this, we can fill in the gaps of climate models to better represent how much solar radiation is reflected by clouds and how much reaches the Southern Ocean.

Mapping Southern Ocean dynamics

Nilas.org is a publicly-available interactive Southern Ocean mapping platform to support research and operational activities within the Antarctic sea-ice zone. It was developed by AAPP/Australian Antarctic Division researchers Sean Chua, Anton Steketee and Petra Heil. The platform provides a user-friendly interface that visualises multiple layers of physical and biogeochemical variables. These variables are primarily derived from remotely sensed products and are updated as new source data become available.

Nilas.org's distinct contribution lies in its ability to provide an integrated view of the Southern Ocean's dynamic environment, thereby enabling a more comprehensive understanding of complex climate processes. By consolidating disparate datasets—such as sea ice, chlorophyll, and sea-surface temperature—into a single, interactive interface, the tool allows researchers to identify correlations and patterns that might otherwise be overlooked when data sources are fragmented. This directly supports the AAPP's core mission of improving understanding of Antarctica's pivotal role in the global climate system.

The most important ice
you've never heard of

Our sea-ice scientists led the first-ever broad review of Antarctic ‘landfast’ ice — the critically important but often overlooked stationary sea ice fastened to the coast. Their research also shows a dramatic crash in the extent of landfast ice in 2022. Much of the ice lost had been present for the previous 20 years.

Despite the critical importance of Antarctic landfast ice for a wide variety of coastal processes, our knowledge of it is limited either spatially (e.g. covering a small study region), temporally (e.g. a snapshot, or covering only some part of the annual cycle), or both.

Landfast ice (fast ice) forms when sea ice mechanically affixes to stable points around the Antarctic continent. Points of stability can either be the Antarctic coastline itself, or icebergs which run aground on the relatively shallow continental shelf (at depths of up to around 400 m).

There are likely around 10,000 such grounded icebergs, but they have never been mapped. Without knowledge of their distribution on the continental shelf, we are essentially unable to model fast ice in our Earth system models, or forecast how it might change under climate change scenarios into the 21st century.

Given the reliance of emperor penguins on fast ice for breeding success, combined with the crash in summertime fast-ice extent observed over the past three years (see above), it is important for AAPP to address this major knowledge gap.

First National Climate Risk Assessment

A technical report about climate change impacts in the Antarctic and Southern Ocean regions, largely by AAPP authors, was a key input to Australia’s first National Climate Risk Assessment. It revealed that a rapidly changing Antarctica will drive some of the major impacts on Australia in the next 25 years.

“Understanding what is happening in Antarctica and the Southern Ocean in response to climate change is a key to understanding future climate change impacts in Australia and globally”, the report states.

Coordinating author, Adjunct Professor Tas van Ommen at the AAPP, said the report underlines the integral role played by Antarctica and the Southern Ocean as a driver of the global climate system as well as a responder to the forces of climate change.

“The National Climate Risk Assessment highlights that 1.5 million Australians could be at risk from sea-level rise by 2050.”

“Our report makes clear that the most significant hazard coming from the Antarctic Ice Sheet in a warming world is sea-level rise around Australia and globally.”

“Many of the deepest uncertainties in projecting how Antarctic ice will respond to global heating and add to future sea-level rise in the long term come from East Antarctica, which covers the 42% of the continent within Australian Antarctic Territory.”

“One of the most valuable parts of our work has also been to identify the gaps in knowledge and modelling that will make a fuller risk assessment possible in the future.”

“While satellite measurements of sea ice and robotic measurements under ice shelves are critical, having boots on the ice for in-situ observations remains crucially important”, Prof van Ommen said.

Profiling the ocean

Over decades, Antarctica has been losing ice mass as warmer waters erode it from below. In turn, meltwater from the ice changes the density of the ocean and the way the ocean moves and transports heat, nutrients and carbon. We want to know how changes in ocean circulation and temperature will affect East Antarctic ice shelves by understanding the processes that are transporting heat polewards across the Southern Ocean.

The main way we trace different ‘water masses’ in the ocean is with CTD sampling (standing for Conductivity-Temperature-Depth). During the two-month Denman Marine Voyage in 2025, for example, our oceanography team completed more than a hundred CTD deployments — and due to the low sea ice, closer to the Denman Glacier than expected.

In addition to ship-board sampling, we use different kinds of robotic Argo floats to profile the Southern Ocean year-round. During the MISO voyage, we deployed 12 Deep Argo floats capable of measuring the full ocean depth, from sea surface to sea floor. These will revolutionise our understanding of the abyss and the cold, dense water masses that fill it. We also released 10 BGC Argo floats to measure the upper 2000 metres of the ocean with biogeochemical sensors.

In 2025, three mooring stations were anchored around the Denman Glacier and Shackleton ice shelf, which will monitor a cross-section of the ocean over the next few years and complement the mooring deployed through the ice shelf. This will enable us to coordinate measurements of melt rates under the ice shelf and oceanic properties at same time.

With the SWOT satellite detecting slight changes in the height of the ocean, we are developing a new understanding of the fine-scale processes in the Southern Ocean. By pairing the satellite data from the surface with measurements from the water column, we can develop a three-dimensional picture of the ocean’s internal circulation.

Sea-ice decline

AAPP scientists have produced the first synthesis of the global impacts of Antarctic summer sea-ice lows. These extreme events have substantial impacts across physical, ecological, and societal systems, from ocean warming and increased iceberg calving rates, through to habitat loss for higher-order predators, and logistical challenges for national Antarctic programs.

While our knowledge of the southern polar region and its ecosystems is increasing, we don’t yet sufficiently understand the baseline system to predict how it will respond to the dramatic changes we’re already observing. Using satellite data combined with other AAPP oceanographic and atmospheric data, in addition to ship-based and on-ice fieldwork, we are building a better understanding of the ocean-sea ice-atmosphere-biology system.

Extreme lows in sea ice induce many changes in the physical, ecological, and societal systems of Antarctica and the Southern Ocean. a) an average sea ice summer. b) an extreme low sea ice summer. In b), fast ice and pack ice have both retreated, ice floes within the pack ice are smaller, the surface albedo has decreased, and the surface ocean has warmed. There is also an increase in precipitation over the ice shelf. The reduction in sea ice has exposed the ice shelf to ocean waves, inducing fractures near the calving front, and leading to increased iceberg calving. There is a transition from sea ice associated productivity in a) to open ocean productivity in b) with a concomitant reduction in krill and silverfish biomass. In b), the seals are forced to seek shelter on smaller ice floes, while much of the landfast ice used by the penguins in a) has disappeared in b). In b), an opportunistic tourist vessel visits a region that was previously inaccessible due to ice cover. (from PNAS Nexus)