Research

My research ranges from analysis of in situ oceanographic observations to developing projections of global rainfall changes. Below I list a number of recently funded projects I am involved in and which reflect my current research focus. For a more complete picture of my research interests and experience see my publications.

Understanding spread in sea level rise projections

Funded by the Australian Research Council from January 2016 and led by Catia Dominguez at the University of Tasmania.

Sea level rise projections for this 21st century largely disagree in magnitude and spatial changes between climate models, particularly in hotspots. This project aims to investigate changes in water properties and ocean circulation mechanisms leading to inter-model spread in sea level projections. The expected outcomes will contribute towards more rigorous constraints on the likelihood of future warming and sea level rise projections, and are aligned with scientific deliverables required to address key questions in support of Australia’s climate change policy. They are also aligned with international scientific deliverables in support of the World Climate Research Programme Grand Challenge on Regional Sea Level Change and Coastal Impacts.

Fig: (a) Ensemble mean and (b) ensemble standard deviation of climate model projections of change ∆ζ in dynamic sea-level for 2081–2100 with respect to 1986–2005 under a mid-range scenario, expressed as percentages of ensemble-mean global-mean sea-level rise hθ due to thermal expansion for the same scenario. From Gregory et al. 2016 doi:10.5194/gmd-2016-122.

A thermodynamic view of ocean warming

Funded by the Natural Environment Research Council for 5 years from October 2015, this project will:

  • Diagnose the ocean’s vertical heat balance, including the contributions due to different components of ocean circulation, in a range of state-of-the-art ocean climate models using novel water mass based methods.
  • Place observational constraints on the contributions to the vertical heat alance using inverse methods and statistical techniques.
  • Diagnose how the ocean redistributes heat vertically as the surface of the ocean warms in response to anthropogenic forcing and understand how this relates to the mean state of the system.
  • Determine which components of the ocean respond to this forcing ‘passively’ (not changing their circulation) and the potential role of resolved mesoscale variability.
  • Work with 10 ocean modelling groups contributing to international efforts to project future climate, to develop water mass based tools, to help improve ocean models, and to coordinate an ocean warming inter-comparison project amongst those groups.

CLimate scale analysis of Air and Water masses (CLAW)

Three year grant funded by the National Environment Research Council, August 2013

This project is concerned with measuring changes in global rainfall and ensuring that computer models of the climate can predict how rainfall will change in the future.

As carbon dioxide and other greenhouse gases are continually added to the atmosphere, it is understood that the temperature of the surface of the earth will rise. Warmer air can hold more moisture, so as the Earth warms the rate at which the atmosphere extracts water from the surface of the earth and dumps it back as rain will also increase. Knowing precisely how much global rates of rainfall will change into the future is important to many people including farmers wanting to know which crops to plant and nations wanting to build domestic water and hydroelectric infrastructure.

Measuring the total rainfall around the world is no mean feat. On land, measurements are made directly (by catching the rain) or by reliable 'indirect' methods based on river flow and how wet the soil is. However, two-thirds of the globe is covered by ocean. It is hard to catch rain in the middle of the ocean without actually being there to do it. Although many 'indirect' methods exist for measuring rainfall over the ocean there is great uncertainty about how much rainfall has changed over the ocean in the last 50 years or so.

Thankfully there is a solution. The ocean itself acts as a giant rain catcher. Water that falls as rain is fresh water, like the water we drink. Most of the ocean however, is very salty. So the more rain that falls, the fresher the ocean water gets and the more evaporation that occurs the saltier the ocean water gets. Oceanographers can measure just how salty the water in the ocean is and have been doing so regularly for more than 50 years now. The question remains however, how do you turn measurements of the salinity of the ocean into measurement of how much rain has fallen?

By looking all around the globe and counting up how much more salty water there is and how much fresh water there is, researchers can estimate how much water has been evaporated in one place and fallen as rain in another. The researchers involved in this project will do this using all the observations of salinity in the ocean taken over the last 50 years. They will estimate just how much rainfall has changed. They will compare this with computer models which are commonly used to predict what will happen in the future to see how accurate they are and how they can be improved.