Deep sea is slowly heating up

A new study has found deep sea temperatures that scientists have previously thought of. Credit: Doug White

New research suggests that temperatures in the deep sea are more volatile than earlier scientists and that the trend of warming on the ocean floor is now detectable.

In a new study in AGU’s journal Geophysical research paperResearchers analyzed a decade of temperature recordings anchored at four depths in the Argentine basin of the Atlantic Ocean off the coast of Uruguay. The depth represents the range around the average ocean depth of 3,682 m (12,080 ft), with the shallow being 1,360 m (4,460 ft) and the deepest being 4,757 m (15,600 ft).

They found that all sites exhibited a warming trend of between 0.02 to 0.04 ° C per decade between 2009 and 2019 – a significant warming trend in the deep sea where temperature fluctuations typically measured in the thousandths of a degree goes. According to the study authors, this increase is consistent with warming trends in the shallow ocean associated with anthropogenic climate change, but more research is needed to understand what the rising sea temperature is.

“In previous years, everyone believed there was silence in the deep sea. There was no movement. There were no changes,” said NOAA Atlantic Oceanographic and Meteorological Laboratory oceanographer Chris Meinen and the lead author of the new study. “But every time we look we find that the sea is more complex than we thought.”

Deep gauge challenge

Researchers today are monitoring the top 2,000 meters (6,560 ft) of the ocean more closely than ever before, in large part due to an international program called the Global Ocean Observation System. Instruments called the Argo drown and rise in the upper seas, which collide in ocean currents, providing a rich ensemble of continuous data on temperature and salinity.

However, it is difficult to enter the deep sea and expensive to study. Scientists typically take their temperature using vessels that reduce seafloor just once every ten years. This means that scientists behind their knowledge of the surface have an understanding of the day-to-day changes in the lower half of the ocean.

Maine is part of a team at NOAA conducting a rare long-term study at the bottom of the sea, but until recently the team thought that the four instruments they sang in the lower part of the Argentine Basin would only collect information about the ocean Were staying. Meenen then observed in a study at the University of Rhode Island that he exhibited a feature of the device he was completely unaware of. A temperature sensor was built into the pressure sensor of the instrument used to study the currents and incidentally collect temperature data for the entirety of their study. They only had to analyze the data they already had.

“So we went back and we calibrated all our hourly data from these devices and put together what is essentially a 10-year-long record of temperatures at one meter above sea temperature.”

Dynamic depth

Researchers found at two shallow depths of 1,500 and 3,535 meters (4,460 ft and 11,600 ft), the temperature increased monthly to about one degree Celsius. At depths below 4,500 m (14,760 ft), temperature fluctuations were more minute, but the changes followed an annual pattern, indicating that there is still a measurable effect of weather below the surface of the weather. . Average temperatures at all four locations increased during the decade, but an increase of approximately 0.02 ° C per decade was statistically significant at a depth of only 4,500 m.

According to the authors, these results suggest that scientists need to take deep sea temperatures at least once a year and take meaningful long-term trends to keep track of these fluctuations. Meanwhile, other people around the world who have used the same mooring to study deep sea water streams can analyze their own data and compare temperature trends of other ocean basins Huh.

“There are a number of studies around the world where such data has been collected, but it was never seen,” Meenen said. “I am hoping that this is going to try to lead to a reanalysis of many historical datasets and to see what we can say about deep sea temperature variability.”

There may be implications for a better understanding of the temperature in the deep sea that reaches beyond the ocean. Because the world’s oceans absorb much of the world’s heat, knowing about ocean temperature trends can help researchers better understand temperature fluctuations in the atmosphere.

“We are trying to create a better Global Ocean Observing System so that we can predict better weather in the future.” “At the moment we can’t really make accurate seasonal forecasts, but hopefully as soon as we get better predictions, we’ll be able to tell farmers in the Midwest that it’s a wet spring and you want to plant your crops accordingly.”

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more information:
Christopher S. Meinen et al, Oceanview bottom temperature variability at four sites in the Northwestern Argentine Basin: Evidence between decadal deep / abyssal warming for international variability during 2009–2019. Geophysical research paper (2020). DOI: 10.1029 / 2020GL089093

Provided by the American Geophysical Union

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