Deep-sea Warming
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Deep-sea warming accelerates, threatening ocean ecosystems

The evidence is clear that our planet’s oceans are warming. During the past 60 years, oceans warmed by about 0.7 degrees Celsius. However, much of the data supporting this observation reflects surface and near-surface temperatures. The deep oceans warm more slowly than the surface waters, but they are heating up also. Rapid deep-sea warming poses environmental threats to the ecosystems that thrive there, and a recent study predicts that deep ocean temperature increases will accelerate considerably by 2050.

Studies of climate velocity were the basis for the predictions of accelerated deep-sea warming. Climate velocity measures the speed and direction of species shifts in response to a warming environment. The work found that between 1955 and 2005, climate velocities for deep ocean species were faster than for surface species. 

Deep-sea environment

The earth’s oceans are vast, and for the most part, environmentally stable. But extreme pressures of over 2 million pounds per square foot greet visitors in some of the deepest parts of the ocean, and it is also very cold. The average temperatures in the deep ocean vary between 0 and 3 degrees Celsius (32 – 37.5 degrees Fahrenheit). So, conditions are harsh but stable. However, stability is a two-edge sword that makes deep ocean ecosystems more susceptible to warming.

These deep-sea ecosystems evolved over millions of years, and the species living there optimized their physiology to the existing environmental conditions. The thermal stability within these ecosystems makes these organisms extremely vulnerable to temperature change. Species optimized for 3 degrees Celsius migrate deeper (if possible) when their environment warms. When some species shift, others that feed on them need to also move, thus disrupting the food chain. 

Deep-sea environments are also slow to recover from damage or stress. The DISCOL area in the tropical East Pacific Ocean, 3000 kilometers west of Peru, was the geographical setting for an experiment in 1989. At that time, researchers simulated mining disturbances on the seafloor by plowing up the ocean-bottom sediments 4000 meters below the surface. When the experimental site was revisited 26 years later, sampling showed that the seafloor ecosystem had only recovered by 50 percent. Rapid adaptation is not a forte of deep-sea ecosystems.

Horizontal and vertical migration

Marine species living near the ocean’s surface are shifting poleward to cooler waters in response to rising ocean temperatures. This horizontal migration is documented in both the Pacific and Atlantic oceans. But some species also have the option of migrating vertically since ocean waters cool with depth. For species living in the mid-ocean, between the surface and the seafloor, populations can easily shift horizontally or vertically.

Remember, seafood provides nearly 3 billion people on our planet with a significant part of their daily protein. When commercial fish populations move, then international fisheries are disrupted. Disputes about fishing rights are already underway in the North Atlantic as commercially valuable species migrate across human-made boundaries. Deep-sea warming will force more marine species to move horizontally and vertically in the oceans; therefore, we can expect more disputes as heat disrupts these deep-water ecosystems.


ArcheanWeb:

Seafloor ecosystems fare poorly in simulated deep-sea mining (Source: ArcheanWeb) – https://archeanweb.com/2020/05/05/seafloor-ecosystems-fare-poorly-in-simulated-deep-sea-mining/  Also:

Changing currents cause North Atlantic ecosystem drift (Source: ArcheanWeb) – https://archeanweb.com/2020/05/07/changing-currents-cause-north-atlantic-ecosystem-drift/ Also:


Sources:

Ocean likely to heat up at 7 times its current rate, new study finds (By Jordan Davidson; World Economic Forum) – https://www.weforum.org/agenda/2020/06/oceans-heat-up-seven-times-greenhouse-emissions  Also:

Climate velocity reveals increasing exposure of deep-ocean biodiversity to future warming (By: Isaac Brito-Morales, David S. Schoeman, Jorge García Molinos, Michael T. Burrows, Carissa J. Klein, Nur Arafeh-Dalmau, Kristin Kaschner, Cristina Garilao, Kathleen Kesner-Reyes & Anthony J. Richardson; Nature Climate Change) – https://www.nature.com/articles/s41558-020-0773-5  Also:

Temperature of Ocean Water (Source: Windows to the Universe) – https://www.windows2universe.org/earth/Water/temp.html  Also:

Feature Image: Photostomias (Modified) – By derivative work: Una SmithPhotostomias.jpg: Edith Widder/HBOI – Photostomias.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4153364  

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.