Picture: Looking up to the ocean surface. Credit: Marek Okon (Unsplash).
At such a difficult time, it seems appropriate to open this report in a positive way by celebrating the many successes of the past few months.
We were delighted to see two members of our program feature in this year’s AMOS awards presentation with Ariaan Purich receiving the AMOS Uwe Radok Medal for her thesis, Understanding the drivers of recent Southern Ocean sea ice and surface temperature trends, and Nerilie Abram receiving the AMOS Priestley Medal. Nerilie had quite a run of wins, receiving a Vice Chancellor’s Award from ANU and also being promoted to full professor.
A big congratulations to Matthew England who was awarded the Royal Society of NSW’s 2019 James Cook Medal. This is one of the Royal Society’s most prestigious awards. It was established in 1947 and is awarded periodically for outstanding contributions to science and human welfare in and for the Southern Hemisphere. He was recognised for his sustained track record of outstanding research that has led to improved predictions of rainfall and climate variability, discoveries of the oceanic drivers of severe drought and flooding rains, and quantification of the impacts of climate change and the fate of ocean pollution. Find out all about it here.
Congratulations also go to Jan Zika who was awarded the Anton Hales Medal by the Australian Academy of Science. You can click here to find out all about the research, the impact that Jan’s work has had, and why the award is well deserved. The video also features Jan playing with Lego blocks, because, as we all know, that is exactly how complex science should always be explained.
Meanwhile, Agus Santoso was recognised internationally, stopping off at the American Meteorological Society meeting in Boston (when travel was still possible) to pick up an Editor’s Award 2020 for reviews in the Journal of Climate. Agus also presented two talks at the meeting.
Our research has also featured prominently in the media recently. As 2019 came to a close, a paper published in Environmental Research Letters led by Rishav Goyal revealed that the Montreal Protocol, signed in 1987 to stop chlorofluorocarbons (CFCs) destroying the ozone layer, now appears to be the first international treaty to successfully slow the rate of global warming. The research team found that thanks to the Protocol, today’s global temperatures are considerably lower. And by mid-century, the Earth will be – on average – at least 1°C cooler than it would have been without the agreement. Mitigation is even greater in regions such as the Arctic, where the avoided warming was found to be as much as 3°C – 4°C. As well as impressive science, it was research that had a message for our policymakers as well.
Another high-profile piece of research led by Nerilie Abram resulted in the world’s longest reconstruction of positive Indian Ocean Dipole events, with a record that extended back to 1240. The research published in Nature revealed that these historically rare events have become much more frequent and intense during the 20th Century, and this situation is expected to worsen if greenhouse gas emissions continue to rise. The study also found that in 1675 a positive IOD event occurred that was up to 42 per cent stronger than the strongest event observed during the instrumental record. Its impacts could be seen in historical documents from Asia produced during this period. Importantly, there is a tight coupling between IOD variability and that of ENSO variability in the Pacific, suggesting recent changes to both – likely a result of climate change – could have significant impacts on Australian conditions.
Research on changes to the Indian Ocean has become increasingly urgent as we begin to realise its important role on Australian climate. Recent modelling work by Annette Stellema and members of the Variability team has found that climate change will lead to all circulation features of the South Indian Ocean, including the Leeuwin Current and Undercurrent, North and South East Madagascar Currents, transport through the Mozambique Channel and Agulhas Current to weaken significantly in the last half of the 21st century should greenhouse gas emissions remain unchecked. This is likely to have important consequences for regional weather and marine resources.
As modelling work of this type gives us insight into future changes that will affect Australia’s climate, it is key to ensure that the results are robust as possible. Work on ENSO processes in the Pacific Ocean by CLEX researcher Dietmar Dommenget and colleagues aims to improve how this important phenomenon is accurately represented. In simulating El Niños our models tend to underestimate the positive (amplifying) zonal surface wind feedback, and the negative (damping) surface-heat flux feedback. These are two of the most important atmospheric processes controlling the evolution of El Nino. A new study by CLEX researchers and colleagues shows that CMIP5 models as a group underestimate the feedbacks by on average 54% when simulating the sea surface temperatures by themselves. However, if they are forced by observed sea-surface temperatures they only underestimate these atmospheric feedbacks on average by 23%. This is caused by the Walker circulation in most climate models being located too far to the west. By highlighting these biases this study can help climate modellers improve climate model simulations of natural climate variability and climate change.
Our research has also explored what were thought to be well-understood climate phenomena and found that perhaps our understanding may not be as clear-cut as previously assumed. One of the most intriguing results of the past few months was an exploration of the Southern Annular Mode (SAM) a pressure shift between Antarctica and Australia. The SAM is considered to be a measure of the position of storm tracks and the jet stream as they move north and south over the Southern Ocean. Depending on its phases it was accepted that the SAM can bring rainfall and storms to Southern Australia or shift them closer to Antarctica.
However, research by Clemens Spensberger, Michael Reeder and colleagues has questioned this assumption, showing the SAM cannot be interpreted as a descriptor of mid-latitude variability and that it has little imprint on the weather of the storm track. Instead, our researchers argue that SAM is really a measure of how strongly the Antarctic couples with the midlatitudes. The results call for caution in relating mid-latitude weather to SAM.
As well as highlighting model biases, the program’s research has also introduced solutions. Recently, PhD student Nic Pittman examined satellite‐based chlorophyll observations, which provide the most comprehensive large‐scale estimate of phytoplankton abundance in the upper ocean. He evaluated the performance of satellite chlorophyll observations in the tropical Pacific Ocean and consequently suggested algorithm improvements. These reduced errors in chlorophyll estimates will provide essential insights into critical processes like primary productivity and biologically driven CO2 transport.
Finally, our researchers played a role in being part of a discipline-wide debate around Southern Ocean fronts as part of a major review. The resulting paper explained how “fronts”, sharp boundaries between water masses, are defined, and what their effects might be on the biology of the Southern Ocean. The authors argued that there was no single “correct” definition, only the correct definition for the problem, and data, at hand. To facilitate future research, they included a “user guide” to help practitioners choose the right definition for their problem. This review will help focus a considerable amount of future research in this region and plays a fundamental role in important research on the Southern Ocean and its influences on climate.
Another international collaboration has seen Agus Santoso working with colleagues from NCAR contribute to Asymmetry and diversity in the pattern, amplitude and duration of El Niño and La Niña as part of the Climate Data Guide. You can find the data, explainer, and figures here.
Continuing on the research front we have also seen the evolution of the PhDs who represent the future of our discipline. Bethany Ellis, handed in her thesis, Holocene climate and ocean variability in the Sunda Strait region of the eastern Indian Ocean as did Fabio Boeira Dias at the University of Tasmania for his work, Mechanisms of ocean heat uptake, transport, and storage in ACCESS-OM2. And as Fabio prepared to move on to a postdoctoral position in Finland, we welcomed three new students. ANU honours students, James Sweetman and Elizabeth Thomas, who will be supervised by Associate Investigator Callum Shakespeare and Nerilie Abram, and Flora Norton who has joined CLEX as a University of Melbourne Masters student. Flora will be looking at Measuring the world’s cleanest air – validating the measurements above the Southern Ocean, with Robyn Schofield.
Finally, we would like to end this report the way it started, with some more good news. We are pleased to say that a team from Monash that includes Shayne McGregor, Dietmar Dommenget, Alex Sen Gupta and Scott Power, were awarded a Discovery Project Grant from the Australian Research Council to focus on improving the credibility of regional sea-level rise projections. It concludes what has certainly been a time of great achievement even as we move into another that promises significant challenges.