Scitech | The Pearl Diver

Observing the deep ocean

The oceans cover 71 per cent of the earth’s surface and absorb 90 per cent of all the heat it accumulates. This makes it a critical component in providing a comprehensive understanding of the effects that climate change may have on our planet. Due to a lack of data collection, scientists have dubbed the ocean as being ‘data poor.’ Traditional methods of data collection involved launching expeditions on specialized ships, deploying buoys, and using data from island or coastal stations. Yet, oceanographers are now starting to use autonomous underwater robots to gather data more easily and effectively.

Jaime Palter – a professor in the Department of Atmospheric and Oceanic Sciences at McGill – and her team, have been taking advantage of their recently acquired observational autonomous underwater glider. Using this new apparatus, they are exploring the role of vertical deep ocean mixing, carbon dioxide and oxygen absorption, and the temperature and freshwater concentration of the ocean. The glider, also referred to as the “Pearl Diver,” is equipped with sensors for measuring oxygen, temperature, and chlorophyll (the pigment found in plant and algae). The data collected is transmitted from the glider to a satellite that is accessed by Palter’s team. The satellite serves as a two-way communication system between the researchers and the glider, allowing them to track its position, receive data in real time, and navigate it towards locations of interest.

The lab’s research focus is set in the Labrador sea, known to have the coldest, saltiest, and densest surface waters in the open ocean of the northern hemisphere. It is a region in which freshwater from the melting ice in the Arctic starts to mix with the saltwater of the north Atlantic ocean.

“In the process of making the water dense by becoming cold and sinking, [Arctic water] also brings in oxygen because it mixes with atmospheric gases and anthropogenic [man made] carbon dioxide,” Palter described. When the cold water sinks from the surface of the ocean to the bottom due to convection (in this case nearly 3,000 metres deep), it mixes and carries oxygen and carbon dioxide into the deep interior of the ocean. This process is sometimes referred to as the ocean ‘taking a deep breath.’ It is rare for the deep ocean’s water to be exposed to the atmosphere. This exposure typically only occurs in certain regions such as the far north or south latitudes.

Only half of humanity’s carbon dioxide emissions stay in the atmosphere, and the rest sinks to the land and ocean. It is because this sinkage only occurs in the areas of deep exchange within the ocean that Palter and her team have set out to observe the Labrador sea, where there is more absorption in terms of relative surface area than in other parts of the world.

During a two week excursion in the summer at Trinity Bay, Newfoundland, Palter successfully tested the glider. This signals the beginning of a multi-year observation program in the service of answering bigger questions about the role of the deep mixing in the Labrador sea. Her group’s research could provide critical pieces of information in understanding the oceans’ roles in storing oxygen, carbon dioxide, and heat, and their subsequent effect on global warming and climate change. The glider project is only one of the multiple research focuses of Palter’s lab. Though the glider currently rests in the hangar, it is expected to launch again next summer.