A team of oceanographers has discovered that the deep sea is heating up. Over the last decade, thermometers fixed at the Atlantic Ocean’s seafloor recorded an average temperature rise of around 0.02°C.
That warming may be caused by human-driven climate change, which has increased the world’s ocean temperatures near the surface by about 1-degree Fahrenheit. That number may sound insignificant, but since the ocean is so large, researchers say it’s equivalent to every second four Hiroshima bombs’ worth of energy entered the seas for the past 25 years.
However, it’s unclear whether the deep sea is getting warmer from climate change, as very little is known about the ocean’s deepest parts. “The deep ocean, below about 2,000 meters, is not very well observed,” said oceanographer Christopher Meinen, of the U.S. National Oceanic & Atmospheric Administration in Miami.
Since the deep sea is hard to reach, research sites typically take the temperature only once per decade. On the other hand, Meinen’s team measured temperatures hourly from 2009 to 2019 using seafloor sensors at four different locations in the Argentine Basin, off of Uruguay’s coast.
Over that decade, the two deepest spots saw a clear trend of warming. Waters 4,757 meters below the surface went from about 32.418°F (0.232°C) to 32.446°F (0.248°C,) while waters 4,540 meters down warmed from an average 32.376°F (0.209°C) to 32.421°F (0.234°C.) Meinen and his team published their findings on September 9 in the journal Geophysical Research Letters.
The warming is more significant near the ocean’s surface, but it takes a drastic amount of heat to create even the smallest bit of warming so deep since warm water rises. While it’s too soon to decide whether human activity is the cause, monitoring these locations and comparing the records with data from other ocean basins may help clarify the matter.
