A synopsis of the SIPHA Town Meeting – 7th July 2006
Outlined below is a summary of views expressed and resulting discussion which took place at the SIPHA Town meeting held in Durham on the 7th July 2006. In this document we outline the conclusions drawn as to the scientific focus of a proposal for a new integrated and interdisciplinary directed programme, the target location for study and the approach to be taken to the budgeting and management of the resulting programme. As such, this document is being circulated to all parties who have expressed an interest in such a programme to illicit further suggestions for scientific scope and specific themes and topics to underpin the full proposal, together with suggestions for approach to adopt to drafting of the full proposal and, in addition, provide a means by which areas of the academic community, under-represented at the Town Meeting for whatever reason, can provide input.
Please send by the 13th November at the latest any comments, views and suggestions to:
Professor Jon Davidson Dr Colin Macpherson Dr Christine Peirce
On behalf of the Subduction Working Group
Introduction - Why are subduction zones important?
A visitor from another planet seeking to understand through focused study how the Earth works, would most likely be directed to a subduction zone. It is here that the most dynamic interactions among the atmosphere, biosphere, hydrosphere and lithosphere are found. Driven by the sinking of lithospheric plates back into the interior of the Earth, there is a continual - but not constant - cycling of material among these reservoirs.
Stresses associated with plate motion cause deformation and seismicity while melts and fluids, generated by changing pressures and temperatures within the sinking plate, cause magmatism and hydrothermal activity. The consequences for society are reflected in both short term hazards – e.g. earthquakes, volcanism, tsunamis, mass wasting etc - and allied longer term effects, such as changing sea level due to stress variations, climate change related to volcanic aerosol loading, and changes in ocean productivity relating to seafloor activity. The dynamic environment of subduction zones creates favourable habitats for organisms – including humans. Rapid recycling of materials produces fertile soils while the diverse topography causes local microclimates and differentiates a myriad of habitats. The concentration of populations around subduction zones, however, means that the inherent hazards are translated into real and significant risks. Indonesia, for instance, is the world’s 4th most populous nation, and it’s most volcanically active. The same volcanoes which produce fertile soils to support a population of 200 million also pose severe hazards to that population. The plate dynamics which generate the volcanoes are also responsible for devastating earthquakes and tsunamis, as recent events have illustrated.
It is here at subduction zones that magmas and crustal fluids produce economic deposits, while the combination of prolific sedimentation and oceanic trenches produces accretionary wedges. It is here that the production of fluids and gases support unique communities of organisms, while vigorous weathering, carbonate subduction and clathrate production are critical controls on the carbon cycle. It is here that the basic long-term additions to the continental crust are manufactured, while the recycling of complementary processed lithospheric material is a major factor in developing mantle heterogeneity.
The natural science community has long recognised the key role played by subduction zone systems in controlling the fluxes among atmosphere-biosphere-hydrosphere and lithosphere, while simultaneously appreciating the complex nature of these interactions. Ironically, we probably understand the largely submarine divergent margin systems (mid-ocean ridges) better than convergent plate margins. This no doubt reflects the extraordinary dependency among and cyclicity between different elements in the system (Figure 1) – volcanoes can clearly affect climate, which can affect sea level, which can affect the state of stress in the lithosphere, which can affect volcanic activity, and so on. We make small shuffling steps (both forward and backward) in our understanding of subduction zones. A quantum leap can only come with an interdisciplinary approach that takes into account the connections among the widely disparate elements of the system and considers their societal and environmental impact.
A community-wide approach to understanding subduction zones
1. Subduction Research in the UK
UK scientists have a long and distinguished record in pioneering many aspects of subduction research. Each of the reservoirs - and the phenomena that operate within or between them as illustrated in Figure 1 - have been studied by researchers in British universities and research organisations. In addition to scientific curiosity this interest has been driven by the UK’s longstanding interests in many regions subject to active or (geologically) recent subduction e.g. the Lesser Antilles, SE Asia and SW Pacific. The result is that UK science can justifiably claim to play a leading international role in conducting subduction-related research. However, out-with preliminary mapping projects in these territories there have been very few efforts to study the phenomenon as a holistic system of integrated and inter-related processes. The UK’s scientists have worked within their own institutions, or with well-established collaborators in a restricted number of UK and foreign institutions. Truly multi-disciplinary research synergising the full range of expertise and resources available within the UK has been neither practical nor attractive due to logistical and financial barriers. The UK is not alone in the approach it has taken; understanding whole system dynamics is a scientifically and logistically daunting task that will require a grounding of scientific excellence and a framework of careful planning and management. The benefits of working on this scale though, would allow the UK to derive maximum effectiveness from existing resources and to assume an agenda-setting role in understanding subduction, and its impacts on society.
Figure 1. Schematics of a subduction zone as an integrated system.
2. Focussing the community: history of developing goals for a national programme
i. 2001 - a Consortium Bid
It is clear that understanding subduction zones as integrated phenomena requires a more interconnected approach than is possible through standard, undirected (mainly “blue skies”) funding programmes. Figure 1 illustrates that understanding the complex interaction of sub-systems that comprise any subduction zone would touch on research interests in diverse fields, extending beyond that of traditional Earth Sciences. Harnessing and integrating such breadth of expertise within the confines of a single Standard grant would be impossible. Even with a large number of inter-related Standard and Small grants, the diversity of problems and the range of skills and expertise required to solve them, such a scale of study would not be successful in understanding the system as a whole without managed overview and integration of results between individual studies. With the current lack of systems and infrastructure to facilitate such integration in an effective and timely manner, progress towards understanding the dynamics and processes of subduction systems as a whole and their societal and environmental impact will continue to be slow. Furthermore, true understanding of the findings of such integrated studies also requires a long-term commitment to their study and to the long-term and repeated observation of the multitude of phenomenon in which subduction processes are manifest, since their timescale of variation is similarly broad. Such longer-term observation is also beyond the scope of “blue skies” funding routes which are, by their very nature, time limited.
By the end of the last century it was clear to most researchers that the absence of such integration is a fundamental barrier to understanding how subduction zone dynamics impact neighbouring environments and populations. Many researchers had reached – and indeed are still at - a point where outstanding scientific questions cannot be resolved within their own disciplines. Traditional boundaries need to be broken down, both to resolve existing unknowns and to provide cross-fertilisation that will generate an understanding of whole subduction systems and the many sub-systems found within them.
Taking advantage of the newly-introduced NERC Consortia bids, a Consortium proposal – Subduction UK – was submitted in 2001. The PIs of this proposal originated principally from the Universities of Durham, Bristol, Cardiff and the British Antarctic Survey. The proposal was multidisciplinary, although focussed mainly on solid Earth areas of geochemistry, petrology and volcanology. A significant amount of planning went into refining this bid’s aims and objectives to permit realistic deliverables within the financial constraints of a Consortium programme.
Although the bid was well-received, the Subduction UK bid was ultimately declined. Feedback indicated that the panel would have liked to see a more holistic approach involving a more diverse cross-section of the Earth Sciences community. Such an increase in scope would involve many more researchers, with a concomitant increase in the resources required to deliver pertinent science. It would also require management oversight to ensure integration of results across disciplines. NERC suggested that this could be achieved by redeveloping the proposal into a Thematic (now “Directed”) Programme. Thus encouraged, we began to develop a broad network of contacts and ideas, which underpin the present initiative.
ii. Meeting of interested principles at the Geological Society, 3rd November 2005
A meeting was held at the Geological Society to inform a Concept Note to NERC (Appendix 1). Targeted representatives from across the community (in terms of both research areas and institutions) were invited and discussion of cross-disciplinary scientific issues was accompanied by consideration of current and future NERC strategies, with input from SISB representatives and those involved in providing policy advice to Government. There was no specific agenda. Natural hazards and risks quickly became an inter-connecting theme for all scales of subduction zone process and temporal and structural-scale of observation.
On the basis of the resulting Concept Note and the perceived interest in a community-wide “subduction” programme, NERC funded a Town Meeting, the results of which form the basis of this report and will form the basis of the embryonic proposal for a new Directed Programme.
iii. Town Meeting; University of Durham, 7th July 2006
The agenda for this meeting is included as Appendix 2. The community was invited via email solicitations, direct advertising and, despite scheduling at the end of term/beginning of summer field season, the meeting was very well attended (~70 researchers representing >20 institutions, with representation from NERC and UKIODP). Email input was also received from many others unable to attend due, primarily, fieldwork-related commitments. Over a 100 individuals expressed an interest in participating in the discussion and any subsequent developments.
The meeting comprised a series of keynote talks outlining international scientific problems in the morning, followed by thematic breakout discussions in the afternoon to focus ideas. These discussions were cross-reported in a final discussion section, from which it was clear that there is:
a) agreement that a cross-disciplinary integrated approach is called for;
b) great enthusiasm for pursuing such an approach via establishment of a Directed Programme;
c) a real niche for such a programme which would be complementary to ongoing international efforts (e.g. MARGINS – see below);
d) an overriding scientific theme or principle which draws together all of the cross disciplinary perspectives on subduction zones, namely the causes and consequences of episodicity in processes and phenomenon; and
e) a niche for developing a programme in which integration of research in science and social science can make a significant and tangible difference to the way natural hazard mitigation is treated in the future.
3. Complementary foci
The largest international programme currently supporting research into subduction zones is the MARGINS initiative of the United States’ National Science Foundation[1], which was conceived in 1988 and implemented over the next 10 years. The stated objective of MARGINS is “to understand the complex interplay of processes that govern the evolution of continental margins”. Within the programme are 3 (of 4) themes which relate to subduction zone processes:
i. S2S (source to sink); a largely sedimentary/stratigraphic research initiative focussing on sedimentary systems, specifically:
· What processes control the rate of sediment and solute production in a dispersal system?
· How does transport through the system alter the magnitude, grain size, and delivery rate to sediment sinks?
· How is variability of sediment production, transport, and accumulation in a dispersal system preserved by the stratigraphic record?
ii. SEIZE (seismogenic zone); a relatively focussed, largely geophysical programme addressing the following questions:
· What is the nature of strong, locked parts of seismogenic zones?
· What are the temporal relationships among stress, strain, and fluid composition throughout the earthquake cycle?
· What controls the up- and down-dip limits of the seismogenic zone?
· What is the nature of tsunamigenic earthquake zone?
· What is the role of large thrust earthquakes in mass flux of material in the subduction system?
iii. SubFac (subduction factory); focuses on material/ elemental fluxes, and is thus largely geochemical in approach:
· How do forcing functions such as convergence rate and upper plate thickness regulate production of magma and fluid from the Subduction Factory?
· How does the volatile cycle (H2O and CO2) impact chemical, physical and biological processes from trench to deep mantle?
· What is the mass balance of chemical species and material across the Subduction Factory, and how does this balance affect continental growth and evolution?
Professors Mark Reagan and Cesar Ranero represented the international community at our town meeting, in particular the MARGINS and European initiatives, on which basis they delivered their keynote talks. The approach adopted by MARGINS was explained and why our Directed Programme would be a major step forward in our potential to understand subduction zones and that it would be entirely complimentary with US and other global initiatives. Three significant differences need to be emphasised.
1. The MARGINS programme is an umbrella funding initiative, essentially ring-fencing money to focus on the specific issues listed above. These are tackled as a series of “blue skies” projects. While there are thematic meetings, there is no strategic direction and integration. Although there is a peer review panel to evaluate funding applications, there is no requirement to deliver data and observations to a central pool, or for researchers funded by the programme to report their findings and discuss them with other participants in the programme.