Shin Tani: Understanding the oceans is much more than an academic exercise


Shin tani
08 June 2016

"We know more about the topography of Mars than we do about the earth’s seafloor," Shin Tani says, and oceans "have a much bigger direct impact on our everyday lives than the surface of Mars." But today, we have the ability to map the world’s seafloor in more detail than ever, and this is crucial for tsunami forecasting, fishing resources, sediment transport, environmental change, mineral extraction and many more areas.

To mark the World Oceans Day (8 June), Wide Angle gives the floor to Vice Admiral (ret) Shin Tani, co-organiser of the Forum for Future Ocean Floor Mapping, in Monaco, from 15 to 17 June 2016.

We know more about the topography of Mars than we do about the earth’s seafloor, partly because resources have been more readily allocated to exploring the surface of other planets and also because mapping beneath water is a complex business, especially at great depths.

Water absorbs, reflects and refracts light to such an extent that it is difficult to “see” through it with visual media for more than a few tens of metres. Huge swathes of the oceans, especially those far removed from coastal and national areas, are still inadequately mapped. Environments such as those beneath the polar ice shelves and pack ice-covered oceans are as unfamiliar to us today as the deep ocean was for pioneering ocean floor mappers over 100 years ago.

But, today, with the advent of satellite mapping and other advances to remote sensing, we have access to an increasingly broad suite of technologies that makes it possible to map the world’s seafloor in more detail than ever – but it needs time, investment and coordination.

In particular, the onus falls on the scientific community to explain to the public and funding bodies just why bathymetry – the study of ocean floor depth and topography – merits more attention.

Photo: Schematic illustration of Swedish icebreaker Oden mapping using multibeam sonar and sub‐bottom profiler. (Illustration Martin Jakobsson)
© Martin Jakobsson

Reasons to focus more resources on ocean mapping are not too hard to find. The oceans are regions that are at least as fascinating and challenging for humans as other environments on this or any other planet and, judging by past experience, hold plenty of surprises for us. They also have a much bigger direct impact on our everyday lives than the surface of Mars.

Bathymetry is of vital importance for navigation and coastal management, of course, but also for a growing number other uses. It is fundamental for studies of deep water circulation, tides, tsunami forecasting, upwelling of cold water from lower depths, fishing resources, wave action, sediment transport, environmental change, slope stability, palaeoceanography, site selection for platforms, cables, pipelines and offshore wind turbines, waste disposal, mineral extraction and many more areas.

Perhaps the easiest case to make from a commercial perspective is that the better our knowledge of the ocean floor, the more effectively we will be able to manage marine environments to ensure we carry out fishing in a sustainable and productive manner. Bathymetry is crucial to our understanding of the bottom habitats of sea life. Better knowledge of the oceans also helps to make the operations of extractive industries companies more efficient and safer. 

But, of course, the utility of ocean floor mapping goes far beyond purely commercial concerns. To take the example of the study of tsunamis, if scientists know more about the contours of the seafloor and ocean depths, then predicting how the vast bodies of water disrupted by sub-sea earthquakes will behave should become more accurate. The modelling of tsunami propagation requires both deep ocean bathymetry and high resolution mapping near shore to provide a complete picture of how water will be moved from deep to shallow water and how it will impact the coast.

Better ocean floor mapping will not improve our ability to predict when tsunamis happen, as they are triggered by seismological events, but it should give us more information on their direction of travel and likely severity once they have formed.   

Photo: Shallow water bathymetry of the Venice.
© Marzia Rovere

Improving understanding of environmental change

Ocean floor mapping is also a vital tool in efforts to track and predict longer-term environmental changes, which will have a major impact on our lives. We know climate change is occurring, the oceans have become warmer and that ocean currents have changed. How these events are interlinked is subject to debate, but we do know they are happening and we need to address their impacts.  

A good example of how improved knowledge of bathymetry can help us here is work being carried out in the fjords of Greenland and in Antarctica, where most of the world’s ice is located. We have measured, and begun to see, the effect of the inflow of warmer ocean water towards the outlet glaciers of the Greenland and Antarctic ice sheets. The results are thinning glaciers, large calving events (where part of the ice sheet becomes detached), massive ice break ups and glacial retreats. This process can be seen in action at locations such as Jakobshavn in west Greenland and Pine Island Bay in west Antarctica.

These events lead to increased acceleration of the ice streams draining the glaciers and ice sheets, which in turn contributes to sea level rise. The scale and rate of that sea level rise is hard to predict, which is why we need to look at as many factors as possible, including the rate of ice melt, to make forecasting more accurate.

So where does the bathymetry come in? We need to know the sill depths of the fjords and the access points where warmer sub-surface water can get in and flow towards the glacier, or, in the case of an ice shelf, underneath it. But these areas are extremely poorly mapped.

In some fjords we have virtually no bathymetry at all, and for regions underneath ice shelves, data mainly stems from sporadic experimental forays by autonomous underwater vehicles. Improved ocean floor mapping in these areas will bring greater understanding of extremely complex processes.

Recent developments in multibeam sonar mapping – pinging sound pulses off the seabed using instruments based on vessels – have increased the resolution with which the seafloor can be mapped by so much that previously obtained data has been made virtually obsolete. Scientific conclusions based on sparse bathymetric information need to be re-examined and refined. Only around 11% of the Arctic has been mapped with multibeam, leaving a vast swathe of the region that needs to be mapped in this way to ensure that all marine activities in the region benefit fully. The cost of using multibeam technology has fallen sharply since it was first used in the 1960s and 1970s making it a more economical proposition.

Meanwhile, other techniques, such as geodesy – or gravity mapping – from satellites are also coming into their own. By calculating anomalies in gravitational fields, this process can highlight peaks and troughs on the seabed.   

But mapping wide areas can only be achieved through international coordination and collaboration involving the scientific community, naval institutions, and industry.

Photo: Mounted high‐resolution multibeam sonar on the sailing vessel "Exploder of Sweden" during the expedition VEGA 2013, Northwestern Greenland.
© Martin Jakobsson

Spreading the word

There is no doubting the value of improved knowledge of our oceans, so it is good to see that two events are being held in June aim to add to that knowledge of the oceans and explain why doing even more is crucial to our future.

On June 8, we celebrate World Oceans Day, which is a timely reminder of the importance of the sea in all our lives – not least because they are the lungs of our planet, providing most of the oxygen we breathe – as well as providing a platform to inform the public on the impact of human actions on the ocean.

This year a series of events are being built around the theme “Healthy Oceans, Healthy Planet”. The emphasis is on the impact of human pressure on the sea, which is leading to overexploitation, illegal, unregulated and destructive fishing, unsustainable aquaculture practices, marine pollution, habitat destruction, the introduction of alien species into well-established ecosystems, climate change effects and ocean acidification.

Then on June 15-17, the Forum for Future Ocean Floor Mapping  is being held in Monaco. This meeting of experts in the field from across the academic and commercial worlds provides a platform for the acceleration of ocean mapping, which is essential if we are truly to understand the way our oceans work. The forum has been organised by the Nippon Foundation, Japan’s largest private philanthropic foundation, and the General Bathymetric Chart of the Oceans (GEBCO), a unique organisation at the heart of the drive to map the world’s seabed from the coast to the deepest trench.

The Nippon Foundation has been involved in maritime issues for many years and its chairman, Yohei Sasakawa, was awarded the prestigious International Maritime Prize for 2014 by the International Maritime Organization (IMO) for his contribution to supporting the development of future maritime leaders and for enhancing safety and security in vital shipping lanes.

Founded by a group led by Prince Albert I of Monaco and Professor Julien Thoulet of the University of Nancy in the first decade of the 20th century, GEBCO is an independent, non-profit making body under the joint auspices of the International Hydrographic Organization (IHO) and the Intergovernmental Oceanographic Commission of UNESCO (IOC). It is ideally placed to act as a central repository and forum for global ocean mapping-related information, products and expertise for a theme that stretches across national boundaries and requires coordinating accordingly. Through GEBCO, the scientific community can prioritise areas of greatest need and increase the profile of bathymetry in inter-governmental forums and other meetings. Over recent decades the organisation has developed a series of bathymetric charts, including, in 1994, the GEBCO Digital Atlas (GDA), which represented the first seamless, high-quality, digital bathymetric contour chart of the world's oceans and now provides the basis for regular updating of GEBCO, the most recent of which was in 2015. 

Photo: Since 1903, five separate editions of paper, bathymetric contour charts covering the whole world have been produced. GEBCO is now maintained in digital form as the GEBCO Digital Atlas.

Enhancing our knowledge of the way the oceans work has never been more important. Doing so will improve our ability to predict and prepare for environmental change and make better use of our maritime resources. Both the UN’s World Oceans Day initiative and GEBCO’s Forum for Future Ocean Floor Mapping provide much needed exposure for this vital component of our planet’s ecosystem.

Shin Tani

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Vice Admiral (ret) Shin Tani is the current Chairman of the joint IHO-IOC GEBCO Guiding Committee since October 2013. Before that, he has made a major contribution to GEBCO’s work and activities for more than 24 years. He holds a Master of Science (MSc) in Geophysics from the Post Graduate School of Kyoto University, obtained in1978 and served the Japan Coast Guard as Vice Admiral. He is the 44th Chief Hydrographer of Japan since 1871. He is a Member of IHO-IAG ABLOS (Advisory Board on the Law Of the Sea) and served as a member of the UJNR Sea Bottom Surveys Panel from 1979 to 2014. He has been Cabinet Counsellor for the Cabinet Secretariat of the Government of Japan in charge of ocean policy, renewable energy, ocean survey and monitoring, data management, marine cadastre, and UNCLOS Extended Continental Shelf. He was visiting Professor at the Kanazawa University in 2005-2010. He worked at the Japan Oceanographic Data Center (JODC) and the National Geophysical Data Center (NGDC).