Abstract:

The thermal conditions in which coral reefs live are governed by ocean and atmospheric processes that occur over a vast range of scales, ranging from large-scale processes at the scale of ocean basins (order thousands to tens of thousands of km), to regional scale ocean dynamics (order 100 km), to smaller-scale (order km or less) processes occurring at the scale of individual reefs. In this talk I will discuss the role that tides in particular play in regulating temperature variability and thermal extremes within reef environments, focusing on recent research activities in northwestern Australia as a case study of these dynamics.

At the scale of individual reefs, I will discuss how temperature variability within tide-dominated reef habitats (such as those found throughout northern Australia) often differ substantially from the surrounding ocean and how thermal extremes can be accurately predicted (now and in the future) by assessing the mechanisms that control reef heat budgets. Using data from field studies in Kimberley region of northwestern Australia, I will show how a simple heat budget model can be used to investigate how tidal and solar heating cycles interact with reef morphologies to control diurnal temperature extremes within shallow tidally-forced reefs. This model is then extended to show how reefs globally with tidal amplitudes comparable to their depth relative to mean sea level tend to experience the largest temperature extremes. As a consequence, this analysis reveals how even a modest sea level rise can substantially reduce temperature extremes within tide-dominated habitats, more generally.

Finally, on larger (regional scales) I will discuss our current research into the ocean drivers of coral bleaching across northwestern Australia during 2016, and the notable role that tidal mixing in particular played in controlling temperature variability and thermal stress across the region.

Bio: Ryan is an Australian Research Council Future Fellow, a Professor at the University of Western Australia, and a Chief Investigator of the ARC Centre of Excellence for Coral Reef Studies. He has a unique background in coastal oceanography and environmental engineering that enables him to tackle complex (and often multidisciplinary) research problems in coral reef systems. Major areas of research focus include: understanding how ocean dynamics drive physical and other environmental variability within coral reefs; how these dynamics influence a range of complex biophysical processes, and finally how these processes can be numerically predicted and accurately forecast into the future.