August 4, 2018 | Published by | ,

The Climate Variability and Teleconnections Research Program has formed into three separate clusters – SAM, Tropical Variability and Oceans.

The SAM cluster of around 20 researchers has been meeting fortnightly since March 2018, exploring extratropical atmospheric variability and its impacts on surface climate variability and extremes, the Southern Ocean and Antarctic sea-ice.

Meanwhile, the Tropical Variability cluster has sorted itself into five themes with a leader for each theme. These themes and their leaders are ENSO (Andrea Taschetto), Decadal variability (Christine Chung), Climate Change (Chen Li), Extratropics (Kimberley Jane Reid and Zoe Gillett) and Diverse (Claire Vincent). The Diverse theme takes in Madden Julian Oscillation, monsoons, model errors, tropical cyclones, land etc). The fortnightly meetings of the Tropical Variability cluster have been scheduled to the end of 2018 with specific dates set aside for each of the themes.

The Oceans cluster holds weekly Modular Ocean Model (MOM) meetings and the modelling group is also maintaining close connections with COSIMA – the Consortium for Ocean Sea-Ice Modelling in Australia. COSIMA is funded independently of CLEX, but strong synergistic links exist, and many CLEX personnel attended the 3rd annual COSIMA workshop in Canberra in May.

The Climate Variability and Teleconnections RP is already starting to produce the next generation of exceptional young researchers. Zoe Gillett (now a PhD student at Monash) was awarded the Australian Meteorological and Oceanographic Society (AMOS) Regional Centre Award for Academic Achievement for excellence in undergraduate study.

Most of the postdocs, students and associate investigators are now in place and have been linked to clusters depending on their expertise. You can see the full list of new personnel at the conclusion of this newsletter, below. All the elements are now in place with research and modelling work well underway.

 

Model developments

The Oceans cluster is currently evaluating model versions with COSIMA with the aim to produce a model evaluation paper and fully advertised publication release of ACCESS-OM2 this year.

Tropical Variability’s Chen Li is currently developing perturbed physics ensemble with the low-resolution ACCESS-slab-ocean version for climate change simulation with correcting the mean state surface temperatures by flux corrections. This is ongoing work with no results yet to report.

Meanwhile the SAM Cluster is continuing its efforts to produce a pacemaker version of the ACCESS-KPP model.

 

External engagements

The Oceans team has engaged strongly with the national and international climate science community. Nerilie Abram presented at the Continuing Education series on Climate and Climate Change conference, speaking on Australia’s changing climate from the perspective of the last millennium. Nerilie also presented at POLAR2018 along with Claire Krause and Andy Hogg.

As well as travelling internationally, the Climate Variability team has hosted multiple visitors as we seek to deepen our research collaborations. Stephen Griffies visited from GFDL to attend the COSIMA meeting and collaborate with Andy Hogg, while David Munday from the British Antarctic Survey gave a seminar at ANU and met with CLEX postdocs and Axel Timmerman visited Monash in May.

Ellen Corrick an expert in rapid climate change also visited ANU in later April.

 

RESEARCH

SAM cluster

The early research coming out of the SAM cluster has had a strong policy component. Earlier this year a paper led by Andrew King focused on the Paris Agreement targets to see if the estimates of the difference between impacts at 1.5°C and 2°C levels above pre-industrial conditions was linear. Generally the paper found that there was a consistent linear relationship for most regions with the exceptions of North Pacific, northwest Atlantic, northwest Africa and China. Intriguingly they found the difference in these areas was caused by other forcings not related to changes in greenhouse gas conditions, such as aerosols.

A second international paper that drew considerable media attention looked at past impacts on Earth when the planet was 2°C above pre-industrial conditions. It revealed significant changes in every part of the globe and importantly looked at the persistence of these changes due to the momentum of the climate system. The three past analogs of a 2°C warmer world suggest policymakers will need to prepare for changes in the climate and sea level that could continue for hundreds of years.

 

Tropical Variability cluster

Marine heatwaves have been the flavor of the past four months for the Tropical Variablity Cluster, although two papers on ocean oscillations and their impact on weather and climate have been conditionally accepted and will likely appear in the next newsletter.

The first of the marine heatwave papers to be published in Nature Communications was co-authored by researchers from the ARC Centre of Excellence for Climate Extremes (CLEX) and the Institute of Marine and Antarctic Studies (IMAS). It revealed that globally marine heatwaves have increased over the past century in number, length and intensity as a direct result of warming oceans. From 1925-2016, the study found the frequency of marine heatwaves had increased on average by 34% and the length of each heatwave had increased by 17%. Together this led to a 54% increase in the number of marine heatwave days every year. This paper received considerable media attention.

The second paper was about marine heatwaves much closer to home. It looked at marine heatwaves off the east coast of Tasmania, a location recognised as a global warming hotspot. Average sea surface temperatures here have been rising at four times the global average rate and trends in marine heatwaves are showing significant increases in number. The East Australian Current was found to be the dominant driver of heatwaves in this region, with warm air temperatures and northerly winds coming second. The researchers also identified 12 heatwave types, each with its own regional focus, seasonality, and associated large-scale oceanic and atmospheric circulation patterns. This is important research with direct application for the Tasmanian fishing industry.

 

Oceans cluster

The research coming out of the oceans cluster has been quite varied over the past few months and has been supported by some impressive animations.

World-first modeling research by Taimoor Sohail using the NCI’s supercomputer Raijin suggested the Southern Ocean’s ability to absorb heat and carbon from the atmosphere varies significantly from previous estimates due to the way the surface layers mixed with the deep ocean. This research was also important for Australian fisheries as the nutrient rich water rising from the bottom of the ocean boosts ecological activity that underpins much of the oceanic food chain in the Southern Hemisphere. Taimoor along with colleagues Andy Hogg and Bishakhdata Gayen produced a narrated animation showing this work, which you can see on the CLEX website.

Another piece of research that involved an animation by NCI, a new modeling approach and led to significant media coverage, came from an international collaboration developed after a piece of foreign kelp washed up on an Antarctic beach. Previously, it had been assumed that the winds and currents surrounding Antarctica prevented floating objects from the sub Antarctic islands and further north from reaching these shores. But modeling and oceanographic analysis led by Adele Morrison found that with the addition of Stokes Drift – caused by storm generated waves – plays a major role in how drifting objects move through the Southern Ocean. It now suggests the Antarctic is much more vulnerable to biological colonization and human pollution than previously expected.

Marine heatwaves are increasingly being reported but there has been little understanding of how to define the severity of a heatwave. CLEX researchers and colleagues have now defined a severity index for marine heatwaves. It is structured in a similar way to the category definitions for cyclones/hurricanes with the severity of biological impacts being the key distinguishing factor. There are four categories – Category 1 (moderate), Category 2 (strong), Category 3 (severe) and Category 4 (Extreme). The aim of this research is to improve public communication of marine heatwaves, allow early detection of these events and to create a standard convention for naming and understanding heatwaves that can be used consistently by researchers around the world.

One of the more unexpected papers to come out of the oceans group has been an examination of science outreach and social media by new postdoc Amelie Meyer. The research comes from her work with the Norwegian Polar Institute. This paper looks at how to develop outreach via social media and is worth highlighting because of its list of clear tips for any researchers or research projects that hope to develop a public profile on social media.

 

NEW PERSONNEL

Postdocs: Ryan Holmes (UNSW: Mixing in temperature space); Ariaan Purich (UNSW: Sea ice-ocean interactions); Navid Constantinou (ANU: The dynamics of eddy saturation); Amelie Meyer (UTas: Attribution of changing Southern Ocean eddies); Hakase Hayashida (UTas: Biogeochemistry in Southern Ocean models).

 

Students: Taimoor Sohail (ANU: Convection in the Southern Ocean); Josué Martínez Moreno (ANU: Tracking Southern Ocean eddies); Smruti Jena (ANU: Convectively driven circulation of the North Atlantic); Nic Pittman (UTas, June. Tropical Pacific biogeochemistry); Jessica Hargreaves (ANU: Sea surface temperatures and the expansion of the tropical rain belt); Zoe Gillett (Monash: Wintertime subtropical jet interactions); Dawn Yang (Monash: Influence of ENSO on storm tracks); Josué Martínez Moreno (ANU: The affect of climate change in eddies and jets)