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Argo Observations: A Key Component in Climate Change Research

argo observation

Global warming refers to the gradual increase in the Earth’s surface temperature that has been observed since the pre-industrial period (between 1850 and 1900). This phenomenon is primarily caused by human activities, particularly the burning of fossil fuels, which increases the levels of greenhouse gases that trap heat in the Earth’s atmosphere.

It is estimated that human activities have caused the Earth’s global average temperature to increase by approximately 1 degree Celsius (1.8 degrees Fahrenheit) since the pre-industrial period. Additionally, the temperature is currently increasing by more than 0.2 degrees Celsius (0.36 degrees Fahrenheit) per decade.

The current warming trend is without a doubt the result of human activity since the 1950s, and it is happening at an unprecedented rate over thousands of years.

The Essential Role of Ocean Data Collection

Several recent studies have shown that the world’s population is increasingly concerned about the impact of the ocean on our climate system. It is not surprising, then, that many people are curious about the role of the ocean in the current scenario of global change. The ocean plays a crucial part in global warming, as it absorbs about one-third of the carbon dioxide (CO2) that is released into the atmosphere, leading to a rise in ocean acidity. This acidity increase can harm the ocean’s ecosystems and hinder its ability to absorb more CO2 in the future. Moreover, as the ocean’s temperature rises, glaciers and ice sheets melt, which contributes to sea level rise. The warming oceans also affect weather patterns, leading to more extreme weather events such as hurricanes.

Numerous intergovernmental groups, international agencies, research centers, and multidisciplinary groups of experts study the problem from various perspectives to provide clear and forceful information that translates into adequate decision-making by the governments of nations. In March 1991, as a response to the observations of the Second World Climate Conference, the Global Ocean Observing System (GOOS) was created with the aim of observing, modeling, and analyzing marine and oceanic variables. This system provides an accurate description of the state of the oceans with the possibility of forecasting future conditions. Obtaining data collected in real-time is possible thanks to different observation systems distributed globally.

In this context, the international Argo program began in 2000, which includes the NOAA Atlantic Oceanographic and Meteorological Laboratory. This is achieved through a network of drifting floats, which is associated with Jason-3, a satellite mission that supports scientific, commercial and practical applications related to sea level rise, ocean circulation, and climate change. The The name of the program was chosen as a reference to Greek mythology, where Jason sailed on his ship Argo. Currently, there are 4,000 active buoys around the world.

But, How Does The Argo Program Work?

In practice, these drifting floats are distributed throughout the oceans approximately every three degrees of latitude and longitude and record real-time data on temperature and salinity in the first 2000 meters of depth.They have a lithium battery that ensures their operation, and as soon as it runs out, the collection and transmission of data to the satellites is stopped. The useful lifetime is approximately four years, although there are records of active floats for more than five years. When the battery runs out, they usually sink into the ocean and stay there due to the high economic and ecological costs involved in their recovery.

In order to limit the presence of these floats on the ocean floor, some recovery initiatives are being implemented that involves ships that are already in their vicinity and have the possibility of recovering them (ships of opportunity). To facilitate this action, when a low load percentage is detected, the float is configured to remain on the surface and be visible.

Each float measures approximately 1.80 meters in height and 25 centimeters in diameter. They do not need a propulsion system. In addition to advancing horizontally, letting themselves be carried away by the sea currents, they can go up and down, just by changing their buoyancy.

Each float operates in 10-day cycles in the open ocean and 5-cycles in marginal seas.First, it dives up from the surface to the desired initial depth, usually about 1000 meters, where it is carried away by the currents for about nine days. They then submerge to a depth of 2000 meters and automatically begin their ascent to the surface. During this journey, they collect temperature and salinity measurements, which will be transmitted from the surface via satellite to the receiving stations on the ground. Each of the temperature and salinity data sets from 2000 meters down to the surface is called an «oceanographic profile.» With an accuracy of 0.005 degrees for temperature measurements and 0.01 units for salinity measurements, the Argo network provides an extraordinarily detailed description of the state of the ocean and its variations, on time scales ranging from months to decades.

The Ocean’s Surface is Warmer Today Compared to Previous Decades.

Since the beginning of the third millennium, more than 1.5 million oceanographic profiles have been conducted, resulting in a more standardized approach to studying the ocean compared to traditional oceanography conducted aboard research vessels. This information confirms the warming of the global ocean in certain areas, revealing that most of the sea surface is now warmer than in previous decades with a global increase of 0.2 degrees since the mid-20th century. It has also helped to understand this temperature increase in terms of the heat stored in the ocean. By analyzing previous hydrographic data along side data from the Argo network, it has been observed that the accumulated heat content in the first 700 meters of depth has increased over the last 40 years. This increase represents more than 90% of the excess heat from the climate system stored in the oceans.

Heat Content in the Top 700 Meters of the World’s Oceans,1955–2020

Heat Content in the Top 2,000 Meters of the World’s Oceans,1955–2020

It is important to note that all data collected in the Argo program is publicly available for free and can be accessed in less than 24 hours.

Argo has revolutionized the field of oceanography through its network of drifting floats and recently received the Corporate Innovation Award from the Institute of Electrical and Electronics Engineers (IEEE) for its innovation in autonomous observations on a global scale in oceanography with an impact on marine and climate science and technology.

The importance of monitoring the ocean cannot be overstated. Argo and other observation systems provide us with a unique opportunity to gather data that can help us understand the complex interactions between the ocean and the climate system. By investing in such tools, we can take pro active steps to mitigate the effects of climate change and ensure a sustainable future for ourselves and future generations.

 

Sources:
Understanding our planet to benefit humankind (NASA)
Argo Online School
Argo, a window to the Ocean
University of California San Diego
El Programa Internacional Argo (Youtube, Spanish)
Radio Interview on «El Rompeolas», Onda Regional de Murcia (Spanish)
References:
Climate Change Indicators: Ocean Heat. (EPA)
Argo Program. (Atlantic Oceanographic & Meteorological Laboratory)
Global Climate Change. (NASA)

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About the author

Picture of Alberto González

Alberto González

Alberto holds a degree in Marine Sciences and has completed a Master's program in Renewable Energies. He currently works at the Spanish Institute of Oceanography (IEO-CSIC) as a research technician for the Spanish contribution to the Argo Program. His field of study is mainly focused on operational oceanography and physical processes within the ocean.