ANU – Mathematics for Planet Earth

Worth waiting for: ARC grant success for Jan Zika and Matthew England

November 28, 2018November 28, 2018 by Shane, posted in Climate, Latest news, Oceans

Dr Jan Zika (UNSW Mathematics & Statistics) and Prof Matthew England (UNSW Climate Change Research Centre) were awarded $1M in funding in today’s much-awaited announcement by the Australian Research Council. Their Discovery Projects will examine the role of ocean heat content in sea level change and rapid warming near in Antarctica.

Jan’s Discovery Project, “Ocean heat content change and its impact on sea level”, aims to improve projections of possible sea level changes. Poor understanding of the way in which heat is absorbed at the sea surface and distributed by ocean circulation is a leading source of uncertainty in projections of global surface temperature and regional sea level rise by the end of this century. The project, which is a collaboration with Professor John Church (UNSW), Professor Jonathan Gregory (University of Reading, UK), and Dr Xuebin Zhang (CSIRO), aims to transform our ability to predict how ocean temperature and sea level will change in the future.

Matt’s Discovery Project, “Risks of rapid ocean warming at the Antarctic continental margin”, aims to comprehensively understand the interconnected processes by which oceanic heat is circulated towards Antarctica. The risk of rapid ocean warming at the Antarctic margin is profound, with change already detected via deep ocean warming, land-ice melt, and ice shelf collapse. Matt’s project will use high-resolution global and regional ocean/sea-ice models better constrain future rates of ice melt around Antarctica by providing vital knowledge of the ocean processes, dynamics, and feedbacks relating to warm water intrusion onto the Antarctic continental shelf. The project is a collaboration with Dr Andrew Hogg (ANU), Dr Adele Morrison (ANU), Dr Paul Spence (UNSW) and Dr Stephen Griffies (Princeton University, USA).

Full details of today’s ARC grants announcement can be found here.

Dedalus workshop at ANU

August 21, 2018August 20, 2018 by Shane, posted in Latest news, Workshop

Join us in Canberra this Fri Aug 24 for a special workshop on Dedalus, an open-source spectral PDE solver for Python.

Dedalus is a flexible framework for spectrally solving differential equations. Although it was developed for use in fluid dynamics research, Dedalus can be applied to any initial-value, boundary-value, and eigenvalue problems involving nearly arbitrary equations sets. You build a spectrally-representable domain, symbolically specify equations and boundary conditions, select a numerical solver, and go.

The workshop will be held at ANU’s Research School for Earth Science, and will begin with a seminar by Dedalus developer Dr Geoffrey Vallis (U. Sydney), followed by a hands-on workshop.

For more details please contact Taimoor Sohail.

When: Friday 24th August 2018, 1-3pm

Where: Hales Room, Jaeger 7, ANU Research School for Earth Science.

About the main image: Simulation of 2D flow over a wing-shaped obstacle with moderate Reynolds number (Re ~ 100). The flow is visualised by advecting a passive tracer concentration field; released from a perpetual localised source on the left-side of the domain. The wing is implemented with a volume-penalised immersed boundary method. Credit: Eric Hestor (U. Sydney).

To watch a movie of this and other examples, visit the Dedalus Project Vimeo page.

M4PE Seminar: August 27th, Bishakdhatta Gayen (ANU)

August 20, 2018August 20, 2018 by Shane, posted in Climate, Latest news, M4PE Seminar, Oceans, Uncategorized

ARC Future Fellow Dr Bishak Gayen (ANU) will discuss his research in the M4PE seminar at UNSW Sydney on Monday 27 August 2018.

Title: Spanning 10 billion scales from millimetre turbulence to global circulation

Speaker: Bishakhdatta Gayen (Australian National University)

Date & Time: 4pm, Monday 27 August 2018. (Seminar will be followed by refreshments.)

Location: Red Centre room RC-3085, School of Mathematics and Statistics, UNSW Sydney

Abstract: The general ocean circulation, of crucial importance to the global climate, involves fluid motion on scales ranging from turbulence, internal waves, eddies and fronts, planetary Rossby waves and basin-scale gyre recirculation. Equilibrium is maintained between continuous large-scale forcing and energy dissipation. Understanding the physics of various dissipation mechanisms is important for improving the dynamical description of large-scale circulation. Large-scale ocean models do not accurately model turbulent convection, breaking waves, and turbulence, providing motivation to develop a better understanding of these mechanisms. In this presentation, my primary focus will be on understanding the role of turbulence and convection in ocean circulation.

In order to examine the effect of convection in ocean circulation, we have developed a model of circulation with flow driven by surface buoyancy in a closed basin using Direct Numerical Simulations. The circulation cell involves a horizontal boundary flow, turbulent plume motion and week interior return flow. We show that under planetary rotation, even in the absence of wind stress, the flow becomes three-dimensional with small-scale deep convection and broad basin-scale gyres. For the first time, DNS is used to model this circulation and quantify the heat transfer and flow energetics, demonstrating several dynamical regimes. I will also discuss the role of turbulent convection in melting of basal ice shelves and circulation around the Antarctic basin.

About the speaker: Dr Bishakhdatta Gayen is a Research Fellow at the Research School of Earth Sciences at Australian National University. His current research interests are nonlinear internal waves in the ocean, turbulent convection, modeling of Antarctic ice melting and Southern ocean dynamics. Bishak is a 2018 ARC Future Fellow, and has previously been awarded a 2013 ARC DECRA Fellowship. He has also received the RJL Hawke post-doctoral fellowship from the Australian Antarctic Science Program to study subsurface melting of ice shelves around Antarctica with implications for future sea-level rise.

About the main image: A snapshot from simulation of circulation in a closed ocean basin forced by imposed constant temperature having a variation with latitude, showing the kinetic energy on a horizontal plane near the upper boundary, temperature contours on a vertical section near the western boundary and vertical velocity on a vertical section near the northern boundary. Time averaged near-surface transport streamfunction is shown above.