Recovering historical sea level data to help assess risk of extreme sea level events

A Data Rescue Working Group will be established under the auspices of UNESCO’s Intergovernmental Oceanographic Commission and its network Global Sea Level Observing System (GLOSS) to strengthen international cooperation in rescue of historical sea level data.

Historical tide measurements are among the oldest direct observations that provide relevant information on the evolution of mean sea level in the long term. In many countries, systematic sea level observations have been carried out since the early to mid-1800s. Despite this rich historical legacy, documents with these records are hidden in archive centers, which, as all paper documents, are at risk of suddenly going missing.

There can be considerable benefit in rescuing these data before they may be lost. As quoted by Ed Hawkins, Climate Scientist at the University of Reading, UK, “The fastest way to collect new weather observations is by looking back in time!”.

Recovery of historical sea level measurements can contribute to assessing mean sea level trends on multi-decadal to secular timescales. Historical observations can be used to improve estimation and prediction of extreme water levels and are thus vital to coastal management in the context of global climate change.

The Global Sea Level Observing System (GLOSS) of UNESCO’s Intergovernmental Oceanographic Commission has long advocated for the rescue and inventory of historical sea level data. Although individual projects and some concerted national campaigns have been carried out in recent years to respond to these appeals, a more sustained programmatic approach to cooperation in this field is needed at the international level.

The establishment of a Data Rescue Working Group will be the first key step of this new programmatic approach, allowing coordinating international efforts to recover vital sea level data – including, but not limited to mobilizing resources on a large scale for what is ultimately an enormous, time-consuming work.

The Data Rescue Working Group is the main outcome of the international workshop on Sea Level Data Archaeology, which was convened under the auspices of IOC-UNESCO and GLOSS on 10-12 March 2020 in Paris, France. The Tides, Water Level and Currents Working Group (TWCWG) of the International Hydrographic Organization (IHO) and the International Association for the Physical Sciences of the Oceans of the International Union of Geodesy and Geophysics (IAPSO/IUGG) co-sponsored the workshop.

“Ocean observations are essential to understanding and sustainably managing the ocean”, said Vladimir Ryabinin, Executive Secretary of UNESCO’s Intergovernmental Oceanographic Commission during his opening remarks. “Workshops like this are an essential contribution towards the objectives of the United Nations Decade of Ocean Science for Sustainable Development and the World Climate Research Programme Grand Challenge project on Regional Sea Level Change and Coastal Impacts” Ryabinin added.

The Sea Level Data Archaeology Workshop was organized in response to a recommendation by the joint meeting of the TWCWG/IHO and GLOSS (11-13 April 2019, Busan, Republic of Korea).