AMERICAN GEOPHYSICAL UNION
WASHINGTON–New research reveals temperatures in the deep sea fluctuate more than scientists previously thought and a warming trend is now detectable at the bottom of the ocean.
In a new study in AGU’s journal Geophysical Research Letters, researchers analyzed a decade of hourly temperature recordings from moorings anchored at four depths in the Atlantic Ocean’s Argentine Basin off the coast of Uruguay. The depths represent a range around the average ocean depth of 3,682 meters (12,080 feet), with the shallowest at 1,360 meters (4,460 feet) and the deepest at 4,757 meters (15,600 feet).
They found all sites exhibited a warming trend of 0.02 to 0.04 degrees Celsius per decade between 2009 and 2019 – a significant warming trend in the deep sea where temperature fluctuations are typically measured in thousandths of a degree. 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 is driving rising temperatures in the deep ocean.
“In years past, everybody used to assume the deep ocean was quiescent. There was no motion. There were no changes,” said Chris Meinen, an oceanographer at the NOAA Atlantic Oceanographic and Meteorological Laboratory and lead author of the new study. “But each time we go look we find that the ocean is more complex than we thought.”The challenge of measuring the deep
Researchers today are monitoring the top 2,000 meters (6,560 feet) of the ocean more closely than ever before, in large part due to an international program called the Global Ocean Observing System. Devices called Argo floats that sink and rise in the upper ocean, bobbing along in ocean currents, provide a rich trove of continuous data on temperature and salinity.
The deep sea, however, is notoriously difficult to access and expensive to study. Scientists typically take its temperature using ships that lower an instrument to the seafloor just once every ten years. This means scientists’ understanding of the day-to-day changes in the bottom half of the ocean lag far behind their knowledge of the surface.
Meinen is part of a team at NOAA carrying out a rare long-term study at the bottom of the ocean, but until recently, the team thought the four devices they had moored at the bottom of the Argentine Basin were just collecting information on ocean currents. Then Meinen saw a study by the University of Rhode Island showcasing a feature of the device he had been completely unaware of. A temperature sensor was built into the instrument’s pressure sensor used to study currents and had been incidentally collecting temperature data for the entirety of their study. All they had to do was analyze the data they already had.
“So we went back and we calibrated all of our hourly data from these instruments and put together what is essentially a continuous 10-year-long hourly record of temperature one meter off the seafloor,” Meinen said.Dynamic depths
The researchers found at the two shallower depths of 1,360 and 3,535 meters (4,460 feet and 11,600 feet), temperatures fluctuated roughly monthly by up to a degree Celsius. At depths below 4,500 meters (14,760 feet), temperature fluctuations were more minute, but changes followed an annual pattern, indicating seasons still have a measurable impact far below the ocean surface. The average temperature at all four locations went up over the course of the decade, but the increase of about 0.02 degrees Celsius per decade was only statistically significant at depths of over 4,500 meters.
According to the authors, these results demonstrate that scientists need to take the temperature of the deep ocean at least once a year to account for these fluctuations and pick up on meaningful long-term trends. In the meantime, others around the world who have used the same moorings to study deep sea ocean currents could analyze their own data and compare the temperature trends of other ocean basins.
“There are a number of studies around the globe where this kind of data has been collected, but it’s never been looked at,” Meinen said. “I’m hoping that this is going to lead to a reanalysis of a number of these historical datasets to try and see what we can say about deep ocean temperature variability.”
A better understanding of temperature in the deep sea could have implications that reach beyond the ocean. Because the world’s oceans absorb so much of the world’s heat, learning about the ocean’s temperature trends can help researchers better understand temperature fluctuations in the atmosphere as well.
“We’re trying to build a better Global Ocean Observing System so that in the future, we’re able to do better weather predictions,” Meinen said. “At the moment we can’t give really accurate seasonal forecasts, but hopefully as we get better predictive capabilities, we’ll be able to say to farmers in the Midwest that it’s going to be a wet spring and you may want to plant your crops accordingly.”
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Notes for Journalists
This research study is freely available through November 15. Download a PDF copy of the paper here. Neither the paper nor this press release is under embargo.
Paper title:
“Observed ocean bottom temperature variability at four sites in the northwestern Argentine Basin: Evidence of decadal deep/abyssal warming amidst hourly to interannual variability during 2009-2019”
Authors:
Christopher S. Meinen, Renellys C. Perez, Shenfu Dong: NOAA Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida, United States;
Alberto R. Piola: Naval Hydrography Service, Buenos Aires, Argentina; University of Buenos Aires, Buenos Aires, Argentina; Franco-Argentine Institute on Studies of Climate and its Impacts, National Council for Scientific and Technical Research, Buenos Aires, Argentina;
Edmo Campos: Oceanographic Institute, University of São Paulo, São Paulo, Brazil; Department of Biology, Chemistry and Environmental Sciences, School of Arts and Sciences, American University of Sharjah, Sharjah, United Arab Emirates.
The following press release and accompanying images are available online at: https://news.agu.org/press-release/the-deep-sea-is-slowly-warming/
It’s the Missing Heat!
We’re doomed!
But how? With increasing calving of Antarctic ice I would expect an increase in cold ocean bottom water offshore Argentina.
“changes followed an annual pattern, indicating seasons still have a measurable impact far below the ocean surface”. Interesting.
Claim: sea surface 5 year running mean temps gallop off towards the edge of the chart. https://www.data.jma.go.jp/gmd/kaiyou/english/long_term_sst_global/glb_warm_e.html
but the increase of about 0.02 degrees Celsius per decade was only statistically significant at depths of over 4,500 meters.
These guys are in a race with the WHO for which of them can change direction more often. I cannot remember the exact years but:
Trenberth: we can’t find the missing heat
Trenberth: we found the missing heat at the bottom of the ocean. We don’t know how it got there without changing any of the temps on the way down.
Trenberth (just recently!): the ocean is stratifying which is preventing heat from getting to the bottom (so it must be hiding somewhere else?)
…and now these guys say its on the bottom again, but again without changing any of the temps on the way down.
Then they mutter something about 0.04 degrees per DECADE needing to be understood in order to better predict WEATHER.
After following these nutters for over a decade my mind has lost the ability to boggle.
“Rising temperatures in the deep ocean”…… have these scientists heard of geothermal activity?
Four sites on the floor of the Atlantic at depths of ~3000m with over 10 years worth of data shows a rise of between 0.02c and 0.04c per decade? Colour me bad but that really isn’t scary!
At least we found out where Trenberth keeps the family joules.
What do you call a bunch of people who failed to read the specifications for the instruments they were deploying?
Mike
In the 19th century, sailors should have used longer ropes on their buckets.
Statistical noise, not a real signal.
Meridional overturning?
The Ocean’s Meridional Overturning Circulation, Schmittner, Chiang, Hemming 2007, downloadable from ResearchGate.
So there is some heat at the bottom of the Ocean. Hard;y suprisimg with the knowledge we have of vents and volcanos.
Now if this increase had occurred all the way to the top, that might have some meaning . Anyway I thought that bottom water moved so slowly that its hundreds of years old.
So what was happening say in 1066. The brass makers of Bagdad perhaps, busy making lots of the dreaded # Emissions # of CO 2.
VK5ELLMJE
And in other news https://www.bbc.co.uk/news/world-australia-54533971
How does heat get to the deep ocean without going through the upper layers first?
Clearly this is BS, unless it is geothermal heating.
The deep ocean is a vast reservoir of CO2 dissolved in the water. It’s around 37 x 10^12 tons. link
As the ocean warms, some of that CO2 will come out of solution and increase the partial pressure in the atmosphere. So, if the deep ocean has been warming up ever since the end of the Little Ice Age that could account for the increase in atmospheric CO2. If the partial pressure of CO2 in the ocean controls the partial pressure of CO2 in the atmosphere, that alone could explain the increase in atmospheric CO2. Because of the vast amount of CO2 in the oceans, human CO2 emissions would be irrelevant.
From time to time folks have wondered the same thing. Here’s an example from Roy Spencer.
0.002 degrees per year?
Temperature fluctuating almost a degree over a month.
Instruments moored in the deep sea for a decade.
How are they calibrated?
Give me a break!
It’s EurekAlarm! of course.
So they must have used thermometers calibrated, accurate and true to at least 1/1000 th of a degree. At sea, actually that deep under the sea.
Or somehow cooked, homogenized the raw data. Like in that cartoon, “And here, a miracle occurs”…
Wasn’t there a paper in the past telling us that the warming water in the depth has an age of around some hundred or more years ?
They won’t tell us that the “heating” is an actual one.
From the article…
“So we went back and we calibrated all of our hourly data from these instruments…”
I would want to hear a lot more about how the intruments were calibrated before taking any notice of this.
Hmm…. A team of researchers designs (or acquires) 4 devices to measure ocean currents, spends a lot of time and money to plant them in the deep blue sea, and the device has built-in thermometer with circuitry to record hourly temperatures. And nobody on the team knows about/has the interest to use this tool for years?
This does not speak well for the competence of the team. Meaning no slight to the one guy who, when he found out about it, is putting it to use. A worthy effort, even if the results to date do not seem significant.
“typically measured in thousandths of a degree”
So how, and for how long, have they been measuring deep sea temperature to a resolution of thousandths of a degree?
“They found all sites exhibited a warming trend of 0.02 to 0.04 degrees Celsius per decade between 2009 and 2019 ”
When I read that, I stopped. They don’t have that level of accuracy. Statistical output based on far too few data points at far too few depths over far too short a time and off a coast too and I bet even after all that, there will still be problems found with their study.
Garbage study, more rent seeking nonsense, they set out to find a trend I do not doubt and it being only 10 years of data, they were GAGGING to make claims based on such a poverty of data, its mind boggling.
I’d like to know more about these sensors. Three miles is a long way down. Ten years is a long service interval. What is their power source? How do they recover the data? Were they purchased from a civilian firm that provided proprietary software without access to source code that could have disclosed the thermometer data handling. (OK, you guessed it, I’m all in for Linux.)
NoTricksZone has discussed a published proxy review which embarrasingly shows practically no ocean warming in the last two centuries:
https://notrickszone.com/2020/10/12/unheralded-global-ocean-2000-year-temperature-reconstruction-reveals-embarrassingly-small-modern-changes/
It also confirms that the oceans were much warmer at the Holocene optimum 8000 years ago (that’s why it’s called the optimum!).
They key paper – McGregor et al 2015 – is behind a paywall but the NTZ post includes the important figures that include significant recent cooling in parts of both the Atlantic and Pacific:
https://www.nature.com/articles/ngeo2510
Absence of recent warming in this review of all (quality controlled) ocean proxies puts the JoshWillisised Argo data in an uncomfortable light – makes it look like a children’s story book by Josh Willis.
Didn’t they follow the scientific literature over the years ?
Seems they think to be the first to research s.th. in and about oceans and never heard about the streams turning around the continents since ever.