With temperatures below -20 degrees Celsius and sea ice over a meter thick, the Arctic winter presents a challenge for researchers seeking to collect basic oceanographic data, such as water conductivity, temperature, and density. Faced with these extreme conditions, scientists have adapted by using unexpected allies: seals.
Since 1999, researchers like Guy Williams, who regularly sails in these regions, have discovered that seals are a valuable source of oceanographic data. Equipping them with micro-CTD devices has facilitated vertical and deep exploration of the oceans, allowing them to measure water structure and other data that would otherwise be nearly impossible to capture in such extreme environments.
The role of seals in data collection
Seals have become key allies for researchers because of their ability to swim freely beneath the ice, where traditional instruments would not reach. Micro-CTD devices designed by the University of St. Andrews allow seals to collect data as they traverse various layers of water. Weighing just a few hundred grams, the devices attach to the seals’ heads with a special resin and remain attached for about a year. Equipped with CTD (conductivity, temperature and depth) sensors, the devices collect and transmit data every four seconds, sending a portion of the information via satellite when the seals surface.
This ingenious method not only provides detailed information about the marine environment beneath the ice, but also allows researchers to monitor the vertical movements of seals, providing valuable real-time data on ocean currents, water circulation, and the location of nutrients.
Key discoveries in the Southern Ocean
An international team led by Williams analyzed data collected by elephant seals between 2011 and 2013 in the East Antarctic region. The data revealed the presence of cold water masses that play a significant role in the circulation of dissolved gases and nutrients throughout the world's oceans. This data also highlighted the importance of ice shelves in regulating global ocean currents, warning that their melting could slow these currents and disrupt nutrient distribution.
The data also showed that, during winter, surface currents, previously thought to be calm due to the ice cover, are more active than previously believed. This is due to the influence of ocean eddies and wind, which increase water mixing and accelerate the transport of heat, carbon, and other key compounds between the surface and the ocean floor. These findings are crucial for a better understanding of the effects of ocean currents on climate change.
Global impact on ocean circulation
One of the most important discoveries was how melting ice shelves affect the formation of dense water, which is key to deep ocean currents. The clean water that rises from the melting ice interferes with the production of this dense, cold water, which could slow global ocean circulation. This process, known as the Atlantic wobble , is vital for regulating the climate worldwide, and any change in its functioning can have catastrophic effects on the global climate.
Thanks to satellite technology and devices attached to seals, scientists have been able to obtain unprecedented measurements , observing how ocean fronts and eddies transport heat from the deepest layers of the ocean to the surface, and vice versa. This vertical heat transport is an essential process for the oceans' heat absorption, which, in turn, mitigates the effects of global warming.
Despite the progress, seals cannot solve all the problems. Although they help identify key patterns in ocean currents, they cannot swim beneath the ice shelves, limiting access to certain key areas for studying Antarctica. However, they continue to provide crucial data to improve understanding of climate change.
Collaboration between researchers around the world and these marine mammals has been instrumental in collecting data in areas inaccessible by traditional means. These measurements not only serve to better understand the marine ecosystem, but also to predict how global ocean currents may change in the future.
As the planet continues to warm, ongoing study of these critical areas is essential. Seals, along with technological advancements such as gliders and state-of-the-art sensors, have proven to be an invaluable resource for oceanographic science. The data collected are not only vital for understanding the interactions between climate and the oceans, but also for predicting how this will affect the entire planet in the coming decades.