OCEAN OXYGEN

Oxygen, a vital gas for all life on the planet, enters the ocean at its surface and spreads throughout. The oxygen content in any volume of ocean water is determined by multiple biological and chemical processes and controlled by ocean dynamics. Breathing water is hard work as water holds far less oxygen than the equivalent volume of air. The physiological performance of marine organisms is highly dependent on their ability to extract oxygen from ambient sea water. Oxygen availability is thus key for marine life. Photosynthesis in the upper, sunlit ocean is a source of oxygen and its production is closely linked to plankton growth, ultimately feeding the fish we eat. Understanding oxygen cycling and detecting oxygen variability and trends are key aspects of tracking ocean health.

The ocean is losing oxygen (around 2% since the 1950s) at an increasing rate. This decline, termed deoxygenation, affects marine life and the largest ecosystems on Earth. Both climate warming (warmer water holds less oxygen) and natural variability play roles that we need to better understand.

There is presently no model able to reproduce the latitudinal distribution of deoxygenation. Projections for future scenarios indicate a 3% to 4% decrease of the global oxygen content by 2100. With that in mind, we have to improve our numerical models and drastically increase the number of oxygen observations in the world ocean.

Ongoing deployment of in situ observing instruments, such as gliders, biogeochemical floats, ships, moorings, and others are bringing new opportunities to investigate the drivers of global (de)oxygenation and the biogeochemical processes that affect oxygen cycling in both coastal and open ocean areas.

In 2021, more than 70 oxygen sensors were deployed on moorings in the subpolar North Atlantic - the region where the deep ocean is taking a deep breath every winter. Every year, about 100 biogeochemical Argo floats (representing 10% of the global Argo Program) equipped with oxygen sensors are deployed, mostly in the Southern Ocean, North Atlantic, Indian Ocean, and Mediterranean Sea.

In 2021, despite the pandemic, the oceanographic community in Chile and Peru has remained mobilized for maintaining and developing the ocean observing system in the South East Pacific, a key region for the energy budget of the planet.

The SEPICAF project (South Eastern Pacific Circulation from Argo Floats) launched in 2019, and supported by French oceanographic institutions, has undertaken regional coordination with universities and research labs in Chile and Peru to maintain a sufficient Argo float density in this region. This allows us to monitor the thermocline circulation and oxygen conditions, and better understand processes driving the variability in the oxygen minimum zone. As the project lead, Dr. Boris Dewitte explains: “The 16 Argo floats we are in charge of deploying are fundamental for reliable oceanic forecasts. Regional collaborations with universities and fishery companies, as well as international scientific collaborations, have been instrumental for designing the deployment strategy.”

TROPICAL PACIFIC OBSERVING SYSTEM 2020

A Regional Pilot

Sustained observations of the Tropical Pacific Ocean have been a priority for nations around the basin for more than 25 years, driven principally by the global climate effects of the El Niño/Southern Oscillation (ENSO), and by the demonstrated prediction skill based on ocean and air-sea interface observations.

The Tropical Pacific Observing System (TPOS) 2020 goals were to redesign and enhance the TPOS, to meet today and future needs of both research and operational centers. It aimed at building a more integrated, modern and robust observing system, taking advantage of new science and technology. The TPOS 2020 project identified gaps in the current system, the variables and scales to be sampled, and areas of needed research. It proposed a redesign, taking full advantage of the diverse remote and in situ techniques available today, considering their complementarity, and fitting them together in an integrated system. It also specified the model and assimilation improvements needed to fully utilize the observations. TPOS 2020 accelerated advancements in technology, and motivated sponsors to make significant investments to many observational and modelling initiatives.

The new TPOS will provide enhanced capabilities for observing upper ocean and air-sea interactions across a diversity of climate regimes, based on enhanced moorings configuration, and a doubling of Argo floats. It will enable a major gain in biogeochemical sampling, and recommends specific observations for the low-latitude western boundary currents and the eastern Pacific where extreme El Niño events develop. The new TPOS will also deliver many gains to accelerate advances in the understanding and prediction of tropical Pacific variability and its profound impacts at regional scales. Improving our forecasting capabilities will positively impact agriculture, water management, marine ecosystems management, human health, and disaster preparedness.

WMO supports TPOS 2020 to meet growing demand for forecasts and services

We need accurate and reliable observations and prediction models from land and sea to meet the ever-increasing demand for more sophisticated weather, water, climate and ocean services, and forecast products, and multi-hazard early warning systems. Implementation of the sustained backbone TPOS is essential if we are to improve our prediction of ENSO cycles and associated extreme events that have profound societal impacts around the globe. It will also underpin efforts to understand and project changes in the ocean and atmosphere, particularly on decadal and longer timescales.

More than 90% of the excess heat trapped by greenhouse gases is stored in the ocean. It is therefore critical to have high-quality, long-term records of sea surface temperature and the deep ocean – especially in areas like the eastern equatorial Pacific where the instrumental record is sparse. We welcome the TPOS 2020 aims to double Argo observations in the tropical Pacific. The TPOS 2020 project will provide substantial input to the World Meteorological Organization Integrated Global Observing System and help close gaps in ocean observations.

SATELLITE-BASED OBSERVATIONS

The satellite network enables us to accurately measure fundamental variables such as ice coverage, ocean color, sea level, ocean surface temperature and salinity. Together with in situ observations, satellites provide foundational knowledge about the ocean environment and enable a wide range of forecasts and services.

Satellite-based sensors are also capable of retrieving ocean surface wind speed and direction, wave height, and sea-surface height anomalies. Typically taken by polar-orbiting satellites, information is gathered in “strips” as the satellites pass over the earth. The data are very important for forecasts and warnings, as well as to understand more about climate change, providing information from some of the gaps in the ocean where no ship or buoy data is available. On October 27, 2020, a low pressure system with hurricane-force winds was located over the north Atlantic west of the United Kingdom. The European Space Agency’s Sentinel-3A observed seas of 18 meters (59 ft in the satellite image), which can pose a risk to vessels at sea. Satellite altimetry complements data from vessels and other observing networks, helping forecasters better understand the scope of such hazards, and validate forecasts and warnings.

Seas from the Sentinel 3-A, 1211 UTC, 27 October 2020, with infrared image from GOES-16 underlaid (wide view). Zoomed view with maximum seas circled. Courtesy, the European Space Agency and NOAA. GOES: “Geostationary Operational Environmental Satellite”

EMERGING NETWORKS GROWTH

During the last few years, emerging networks have developed considerably to meet new observing requirements. For some, the pandemic impacted deployment operations between 2019-2020. Since the launch of the OceanGliders program in 2017, the number of yearly glider deployments has nearly doubled. This great improvement goes along with an increasing number of countries involved in the program and harmonization of the data exchange format that strongly contributes to achieving the FAIR (findability, accessibility, interoperability, and reusability) data principles promoted by the Global Ocean Observing System. While the deployment of Biogeochemical and Deep Argo floats was stable during the last few years, the level of commitments from supporting countries for the next year will enable the expansion of a multidisciplinary Argo program. This expansion, and in particular the Deep mission, requires coordination and long-term funding to optimize efforts and resources towards developing a sustained, globally distributed and integrated observing network. Animal bourne ocean sensors (AniBOS) have been contributing essential ocean observations since 2004 and the number of deployments and observations has almost tripled in this time. While much of the AniBOS effort has been focused in the polar regions, the program is now expanding and includes observations from the tropical ocean. These observations, freely available to the community, enhance an integrated observing system by providing complementary data from regions poorly sampled by other means.

Animal bourne ocean sensors (AniBOS) have been contributing essential ocean observations since 2004 and the number of deployments and observations has almost tripled in this time. While much of the AniBOS effort has been focused in the polar regions, the program is now expanding and includes observations from the tropical ocean. These observations, freely available to the community, enhance an integrated observing system by providing complementary data from regions poorly sampled by other means.

COMMUNITY COLLABORATION

Covid-19 impacts on observing activities

The impacts of Covid-19 on ocean observing networks range from increased time spent on ship expeditions due to quarantine and port restrictions, to cancellations of ship expeditions, resulting in fewer deployments, and limited servicing of equipment. In many cases, particularly in remote areas, regular data collections and ocean observations ceased or were drastically reduced in 2020.

A number of observing communities have risen to the challenge, however. Overturning in the Subpolar North Atlantic Programme (OSNAP) is one example of coordinated efforts to ensure the continuity of ocean observing. OSNAP provides estimation of the overturning volume transport across nominal 60°N and successfully redeployed equipment on 7 cruises between June and November 2020. Another example is the SURVOSTRAL XBT observations program carried out by Australia, France, and the US, which has been collecting critical upper ocean temperature data in the Southern Ocean for nearly 30 years. Covid-19 restrictions required a 14-day quarantine prior to departure, and upon return, significantly increasing time spent on this ship expedition. Under these conditions, maintaining an uninterrupted data collection is an extraordinary achievement.

Strengthening maintenance capacity in the Pacific Islands

“The border closure has actually helped us improve our sea-level station maintenance capability,” notes Ofa Fa’anunu, the Director of Tonga Meteorological Service, referring to one of the 13 permanent sea-level observation stations across the Pacific Islands. Established in partnership with Australia in 1991, these stations provide an indispensable record of in situ sea level and near-real time ocean and climate observations in a region where sea level rise and climate change impacts are of primary concern. The Tonga station was damaged when Category 4 Tropical Cyclone Harold struck in April 2020, but with remote assistance from the Australian Bureau of Meteorology and the Pacific Community (SPC), an in-country team of technicians were able to identify the issue and bring the station back online.

Engaging Alaskan students and local communities

The integration of local communities is a vital piece in sustaining ocean observing, considering local knowledge, and raising awareness of the state of the ocean. The US Interagency/International Arctic Buoy Program (USIABP) is a fundamental component of the Arctic Observing Network, with a diverse outreach program engaging local students and communities in Arctic ocean observations.

Many buoys deployed by USIABP were designed and built by high school students as part of the Sea Cadets Arctic Buoy Program and USIABP works directly with school districts to decorate “Ice Tracker” buoys for deployment. In March 2021, USIABP returned to Utqiaġvik to deploy 10 “Ice Cadets” and other decorated buoys to maintain fundamental Arctic observations. Since its inauguration in 2020, 31 buoys were created and 44 students involved. This year 21 Ice Cadets are joining field projects including tagging of icebergs in Baffin Bay.

TECHNOLOGY DEVELOPMENT

The Data Buoy Cooperation Panel (DBCP) has been tracking progress of a new generation of wave measuring surface drifters. These Directional Wave Spectra Drifters (DWSD^TM) measure 3-D spectra wave and are increasingly supporting the DBCP-Global Drifter Array via the NOAA-funded Global Drifter Program. Dr. Luca Centurioni, Director of the Lagrangian Drifter Laboratory (LDL) at the Scripps Institution of Oceanography (SIO), and developer of the DWSD drifters, says: “Directional wave observations are crucial to understand the role of wave dynamics in ocean-atmosphere coupling. As part of extreme weather events studies, we have air-deployed several DWSDs under hurricanes and atmospheric rivers, and with ships in areas of intense ocean cooling.”

CALL FOR ACTION

This year we note the continued progress of developing our global ocean observing system despite the significant challenges of responding to a global pandemic.

Thanks to all the implementers and funders for this remarkable development!

Looking ahead, we must continue to increase cooperation and coordination across the international community, and engage more fully with the private sector.

Testing and entraining new lower-cost technologies and multidisciplinary observations globally will enable new discoveries, monitor changes in remote parts of the ocean, and increase system resiliency.

Increasing capacity within indigenous and underserved populations and local communities to contribute towards, and benefit from, increased ocean knowledge is vital to future sustainable communities.

Finally, we must fully embrace the range of ocean-observing opportunities under the UN Decade of Ocean Science to strengthen the system in support of sustainable ocean development.

Dr David Legler
Chair GOOS Observations Coordination Group