Modelling oceans and icebergs: Journal Club with Professor Visakan Kadirkamanathan

Once a week, the Grantham Scholars meet up for Journal Club. At these informal sessions, the Scholars discuss a particular research paper on a topic that may relate to their own research, or sustainability generally. In the first in a regular series of Journal Club blog posts, Grantham Scholar Angesh Anupam reflects on last Friday’s session, led by one of his Grantham Supervisors, Professor Visakan Kadirkamanathan.

This week’s paper

A century of variation in the dependence of Greenland iceberg calving on ice sheet surface mass balance and regional climate change’ by G.R. Bigg, H.L. Wei, D.J. Wilton, Y. Zho, S.A. Billings, E. Hanna and V. Kadirkamanathan.

angesh-anupamThe Journal Club series organised by the Grantham Centre for Sustainable Futures is really a wonderful opportunity for all the Grantham Scholars to get a broad scholarship and appreciation of the interdisciplinary nature of research work. On Friday 14 November 2014, this event was hosted by the University’s Department of Automatic Control and Systems Engineering and all the Scholars attended it with full enthusiasm.

The paper selected for this occasion was from the journal ‘Proceedings of the Royal Society A’ and the title of this paper was ‘A century of variation in the dependence of Greenland iceberg calving on ice sheet surface mass balance and regional climate change’. This paper was authored by G.R. Bigg, H.L. Wei, D.J. Wilton, Y. Zho, S.A. Billings, E. Hanna and (my lead supervisor) V. Kadirkamanathan.

As the title suggests, this literature deals with Greenland icebergs. A very long record of Greenland iceberg data became available through the International Ice Patrol’s record of icebergs (I48N). This record shows how much I48N varies from year-to-year, and the level of variation has increased significantly over recent decades. This paper uses a technique to identify the mathematical model which should be applied to studies of I48N (specifically, nonlinear system identification technique) and combines models that describe both oceans and icebergs through coupled ocean-iceberg modelling.

Before this work, there was a strong debate about what the dominant causes of the variation in I48N were, and on many occasions, open ocean icebergs melting due to temperature change were perceived to be the biggest cause. This study shows that I48N variability is predominantly caused by fluctuation in discharge from the Greenland ice sheet (GrIS) breaking apart at the edges (or ‘calving’) rather than open ocean icebergs melting, but that their contribution to I48N variability has still varied over the years.

As stated above, this work uses the concept of data driven modelling in the form of nonlinear system identification and this approach can be applied to many areas of food security and sustainability research. In fact, my own project, ‘Computational simulation of plant-soil-water processes for design of agricultural production’, is a very good example where this methodology will be used in modelling the different processes. Hence, there can be several direct or indirect ways in which the approach mentioned in the paper can be effectively used to address the problem of food security.

The main motivation behind choosing this paper was to demonstrate this particular type of modelling approach which can be very useful in many research projects, especially where it is difficult to capture the internal dynamics of the system being studied merely through the involved science within the system. Sometimes, there are many available models which work with a very fine precision in the particular areas they are used to study. The modelling approach discussed in this paper can be used as a glue to link some of the these available models that fall within the remit of the research question.

Before commencing the discussion, most of the Grantham Scholars were a bit perplexed about the choice of this paper, but at the same time they were quite eager to grasp the bigger picture conveyed by this literature. Monica Ortiz will directly be using modelling to understand how climate (in terms of temperature and precipitation) will affect crops. She realised that the paper and discussion were useful to give perspective on the powerful benefits of modelling, even on such large scales. Hannah Sewell made a very nice contribution to the discussion in response to James Thackery – she is intending, through her research, to identify the genes and gene variants which are a part of a much larger network of genes that all interact. These interactions can be modelled mathematically giving greater insight into how these interactions produce the end result – in her case, how the many genes interact to give the stomatal patterning seen in crops in response to carbon dioxide levels. Modelling how much each gene and gene variation affects the density of this stomatal patterning could give researchers more control over it. All other participants also agreed with the potential usefulness of modelling and especially the approach described in the paper.

The overall discussion was very fruitful and all the participants appreciated the importance of data driven modelling and the system identification technique in general. We are looking forward to the next Journal Club meeting on Thursday 20 November to explore another topic in the same fashion.