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The Australian Coastal Zone and Global Change: Research Needs

Australian Academy of Science, Becker House, Canberra. Friday 16 December 1994


Mr John Marshall: I am from the Australian Geological Survey. In terms of LOICZ-JGOFS interaction and the aims of both groups, on the shelf in particular, one of the things that I am quite interested in is the reduction of calcium carbonate as a sink for carbon. On a global scale, if we compare the deep ocean with the continental shelf, in the deep ocean there is a gross imbalance in the amount of carbonate being dissolved and how much is being produced. Basically, where is the source of that excess? A workshop which was held recently in the States indicated that either they got the figures wrong or there is a lot of material being produced in the shelf that eventually finds itself in the deep sea.

A big problem we have in terms of the rates of production of carbonate on the shelf is that there is a quite a variety of ranges. Yet, basically, we just do not know how much carbonate is being produced on the continental shelf. We can make estimates. For example, in Australia probably the range is something like about 0.1 to one kilogram per metre square per year. If you look at a continental shelf the size of Australia, it translates at the lowest level to probably something like about 18 to 24 million tonnes of carbon per year.

The international community is now gearing up to looking at this carbonate project, particularly the imbalance between the deep water and the shallow water. I think with either JGOFS or LOICZ in terms of the carbon flux, that is probably one thing that we should be looking at.

Professor Bruce Thom: Stephan, would you like to comment on those remarks of John Marshall?

Dr Stephan Kempe: I could not agree more that this is a very interesting and challenging problem. But you have seen that essentially the calcium carbonate production by calculative flow tends to form a little source for CO2 to the atmosphere. The same happens on coral reefs. You have local (Inaudible) of carbonate and you have CO2 being expelled to the atmosphere. What we see in calcium carbonate production is mostly replenished by water being input from lower water bodies.

The question is how much of that is (Inaudible) under the influence as yet. At the moment we talk about nutrients and excess particles happening and a pH increase. Then in conjunction with the calcium carbonate production we get into a set of problems here which is then anthropogenically influenced and probably quite interesting. I do not actually know how this complexity then resolves.

Professor Bruce Thom: I think that also comes back to John's last point about the scaling. Do you want to comment about that at all, John, or do you feel you have made your point there. Patrick?

Dr Patrick Holligan: Certainly this is a very interesting problem from all aspects, partly from what Stephan is saying, but also from other aspects as well. There is interest, for instance, in the export of soluble carbonates like aragonite from shelf systems in the deeper waters. In the Pacific, it is of special interest because dissolution can occur in regions in which anthropogenic CO2 is penetrating the surface layers of the ocean.

On a much broader scale and the reason I raise this is that I would love to know information about this - if you look at the palaeo perspective in that region north of Australia, that broad shelf region which was largely dry during the Ice Age, was presumably covered in some sort of terrestrial vegetation I do not know what it was like. It has now become a carbon-producing system, or to some degree a carbon-producing system.

This type of shift at the global scale is very important in the sense that we have never really looked at this transition from shelf areas storing organic material - we are probably talking at a global level in the order of hundreds of gigatonnes of this material which could have been oxidised as sea level rose - and of course, the capacity of those systems today to store calcium carbonate, because it has the reverse effect on carbon dioxide in the atmosphere. So I would raise that problem at a palaeo perspective as well. It is a very interesting one indeed.

Dr Bradley Opdyke: I am at the Department of Geology at the ANU here. I have spent most of my short career doing carbon flux on shallow water carbonate depositions - the effect of CO2 in the atmosphere and that kind of thing. What John was saying before was that this meeting that was held in the US was addressing the imbalance in the alkalinity of surface and deep water. In older deep water there is a lot more alkalinity. The question is: how does it get this higher alkalinity? There is not a balance between (Inaudible) trap data in terms of productivity in the open ocean and what you see from surface deep. So you cannot get higher alkalinity from surface ocean, open ocean productivity. So this alkalinity has to have its source somewhere else. This is what our chairman was just talking about. Perhaps it is transported from shallow shelves in terms of carbonate, aragonite - something soluble like that.

Another thing I would like to address is the fact that in places such as the North West Shelf of Australia not only does organic carbon flip-flop but it is also a carbonate carbon flip-flop in terms of weathering of a large shelf area and becoming a CO2 sink. Then, once the sea level rises, becoming a CO2 source.

Professor Bruce Thom: Thank you for that comment. We are getting close to lunchtime, so maybe one more comment.

Dr Robert Burne: Thank you, Bruce. I would like to make three brief points. Bruce pointed out in his introduction the difficulty of integrating scientific observations into the bureaucratic process. But, from a position within government science within the Australian Geological Survey Organisation, I note that both within our organisation and within other organisations in the Commonwealth Government area CSIRO and so on there is an increasing tendency for politicians and bureaucrats to seek advice on matters from these organisations and, indeed, to encourage strategic research programs that will provide that advice. So I think the situation there is improving. Also the fact that consortia are beginning to form between the various organisations to provide that advice.

Moving on to focus 2 of LOICZ, I am not in favour with the term 'biogeomorphology', though it is very clear what is intended by that, so we do not want to get lost in semantics. The problems of typology and classification are also things that I would like to touch on. Faced with the challenge of having to produce a coastal categorisation for Australia, we have adopted a point of view of seeing coastal geoscience in a sense as being a surrogate to mapping ecosystems - recognising that geoscience provides part of the basis of an ecosystem, an ecosystem being the community plus the environment. The physical element of that environment is reflected in the geoscience and also the dead products of the biology get incorporated into that.

If we use geoscience as a component of the ecosystem and use it as either a surrogate for ecosystem or mapping a component of the ecosystem, you have a conceptual basis to spring off into using this type of mapping towards the aims of the second focus.

Gerry was kind enough to mention the display we have up here. We are adopting an approach which is recommended by LOICZ in trying to establish a typology and, essentially, to use advanced algorithms for processing Landsat data to map the coastal zone of Australia. One of the initiatives in the coastal policy that Gerry mentioned is to provide a coastal atlas for Australia which will be a digital updateable thing. So hopefully our initiatives are moving along the tracks mapped out by LOICZ. We would be more than willing to share our experience and gain from any experience of others by comparing approaches.

Professor Bruce Thom: Thanks, Bob. Just to comment briefly on your first point, I am well aware of various attempts to obtain the support and information and assistance of CSIRO and AGSO and others, but the difficulty that I see, particularly from a state and local government perspective is the increasing difficulties that they have in the funding base that they have to place priorities on getting that support. The New South Wales Government looks like it will terminate its agreement with CSIRO to continue the funding there for New South Wales greenhouse scenario information. Certainly, local governments are increasingly under pressure to continue their interest in these areas. So that is where a lot of the difficulties lie. They are the ones who are making the decisions in many cases.

Stephan, did you wish to comment further on this?

Dr Stephan Kempe: Where does the alkalinity in the ocean come from? That is a really interesting question. Here is an example of the alkalinity field of the North Sea. You see in the corner you have high alkalinities. At first we thought it was a river input but, if you extrapolate that to zero salinity, you get too high an alkalinity signal. So I think this is the emanation of the alkalinity produced by sulphate reduction and the bottom sea sediment which are exactly in this corner. That may also apply to any mangrove sediment system where alkalinity is leaking out and thereby replenishing your system.

Then we have what I call an 'alkalinity pump system' which currently only operates to a large scale in the Black Sea, a little bit in the Santa Barbara basin and some other anaerobic basins, where you have sulphate reduction which produces additional alkalinity which in part, due to the iron which extracts some of the HGS, can leak out of this basin, thereby producing alkalinity and pumping it back to the ocean system which has previously been taken out by calcium carbonate formation and therefore, maybe on longer time scales, closing this loop. At this point we do not quite understand the process.

Professor Bruce Thom: Thank you very much. I think we will close this session at this point. If we could be in a position to return to session 3 at half past one after lunch. John Chappell will then take over the chairing role.