The 2,416th Meeting of the Society

November 15, 2019 at 8:00 PM

Powell Auditorium at the Cosmos Club

Argo: A Flotilla of Autonomous Ocean Sensors

Observing the Oceans' Role in Climate Systems

Dean Roemmich

Distinguished Professor of Oceanography
Scripps Institution of Oceanography
University of California - San Diego

About the Lecture

The era of global-scale ocean observations began with the Challenger Expedition in 1872. As part of its epic voyage around the world HMS Challenger measured the variation of ocean temperature with depth at about 300 stations. From this beginning, oceanography gradually advanced through the 20th century as new research vessels were launched and new observational technologies were developed. The development of autonomous systems and sensors towards the end of the 20th century initiated an on-going explosion of ocean observing technologies and a revolution in the gathering and interpretation of oceanographic data. In particular, instruments for low-power electronic measurement of temperature, salinity, depth and other ocean properties advanced rapidly, providing the foundation for the revolutionary development of autonomous free-drifting profiling instruments capable of making water-column observations over long periods of time, unattended and without the need for ship-borne maintenance.

The Argo Program was designed to exploit these technologies in an array of free drifting, autonomous profiling floats evenly over the global ocean. The first floats were deployed in 2000 and there are now over 3,500 floats operating in the global oceans., cycling between the surface and a depth of 2,000 feet profiling temperature, salinity and other parameters from depth to the surface and then transmitting their location and the profile data via satellite for study in understanding the roles of ocean temperature, salinity, and circulation in climate variability and change.

The Argo Program continues to advance float and sensor technologies for future deployment. Through advanced lithium batteries, energy savings in floats, and enhanced capabilities of Iridium satellite communications, Argo floats now being deployed have lifetimes of 10 years or longer. New Deep Argo floats have been developed to extend Argo observations to the sea floor at depths up to 6000 meters, with improved accuracy and stability. And low power sensors are being developed to measure pH, dissolved oxygen, nitrate, and other properties to enable Argo to address ocean acidification, de-oxygenation and other biogeochemical and ocean ecosystem issues.

The Argo Program now is a partnership of over 30 contributing nations., a structure that provides the resources, capabilities, and global reach needed to build, sustain and improve the array, to capture and store the data, and to ensure that Argo data is freely and immediately available (e.g., via the internet ( Data from Argo now is widely used and has become essential for a variety of basic oceanographic research, climate assessments, operational ocean reanalysis, forecasting and oceanographic education. About twenty operational centers around the world assimilate Argo data into their ocean and coupled forecast models. Nearly 4,000 research papers have been published using Argo data, and Argo data has been an important part of over 300 PhD theses.

Argo is a key element of the Global Ocean Observing System (GOOS), which includes both satellites and in situ ocean networks. Other in situ networks in the GOOS include moored observatories, surface drifters, subsurface ocean gliders, and repeat hydrography by research vessels. Synergies between these elements greatly increase the value of the GOOS.

Looking back to global oceanography’s modest beginnings in the Challenger Expedition, and continuing through the 20th century era of research vessels, the recent explosive growth of autonomous ocean observing, including Argo, is transforming oceanographic science. A comprehensive, global, multi-disciplinary, top-to-bottom ocean observing system is a realistic objective for the next decade.

About the Speaker

Dean Roemmich is Distinguished Professor of Oceanography Emeritus in the Divisions of Integrative Oceanography and Climate, Atmospheric Science, and the Physical Oceanography Division at the Scripps Institution of Oceanography of the University of California – San Diego (SIO). He has been at SIO since 1981. He is a leader of the Argo Program and is coordinator of US Argo Consortium. ( Previously he was Chair and was Co-Chair of the International Argo Steering Team, and he led the original Argo design team.

Dean has served on the NOAA Climate Working Group, the Tropical Pacific Observing System Steering Committee, the U.S. National Academy of Sciences panel on “Sustaining Ocean Observations to Understand Future Changes in Earth’s Climate”, the Pacific Islands Global Ocean Observing System Steering Team, and as a Lead Author for the 5th Assessment Report of the Intergovernmental Panel on Climate Change.

For over 40 years Dean has carried out basic research and teaching in large-scale ocean circulation and climate, implementing new technologies and designing, collecting, and analyzing new datasets in all of the world’s oceans. He is an expert in the general circulation of the oceans and the role of oceans in the climate system, and he is an author on more than 100 research papers.

Dean is the recipient of the American Meteorological Society’s Sverdrup Gold Medal, and the Agassiz Medal of the National Academy of Sciences. He is Fellow of the American Geophysical Union and a member of the National Academy of Engineering.

He earned his BS in Physics from Swarthmore College and his PhD in Oceanography from the MIT Woods Hole Oceanographic Institution Joint Program in Oceanography.