Princeton: Ocean Low Oxygen Zones Shrank During Previous Warm Periods. So Why are Ours Growing?

Essay by Eric Worrall

Yet another mystery for the settled science.

Climate change and ocean oxygen: Oxygen-poor zones shrank under past warm periods, scientists discover

by  Princeton University
AUGUST 31, 2022

In the last 50 years, oxygen-deficient zones in the open ocean have increased. Scientists have attributed this development to rising global temperatures: Less oxygen dissolves in warmer water, and the tropical ocean’s layers can become more stratified.

But now, contrary to widespread expectations, an international team of scientists led by researchers from the Max Planck Institute for Chemistry and Princeton University has discovered that oxygen-deficient zones shrank during long warm periods in the past.

“We had not expected such a clear effect,” said Alexandra Auderset, first author of the new paper in the journal Nature and currently a visiting postdoctoral research fellow at Princeton University. She led the study with Alfredo Martínez-García at the Max Planck Institute for Chemistry in Mainz, as part of a longterm collaboration with Daniel Sigman’s group at Princeton University.

It is not yet clear, however, what this means for the current expansion of the oxygen-deficient open ocean zones, said Auderset. “Unfortunately, we don’t yet know whether our finding of shrinking marine oxygen-deficient zones is applicable to the coming decades or only to the much longer term,” she said. “This is because we have to resolve whether short- or long-term processes were responsible for the change.”

Read more: https://phys.org/news/2022-08-climate-ocean-oxygen-oxygen-poor-zones.html

The abstract of the study;

Enhanced ocean oxygenation during Cenozoic warm periods

Published: 31 August 2022
Alexandra AudersetSimone MorettiBjörn TaphornPia-Rebecca EbnerEmma KastXingchen T. WangRalf SchiebelDaniel M. SigmanGerald H. Haug & Alfredo Martínez-García 

Abstract

Dissolved oxygen (O2) is essential for most ocean ecosystems, fuelling organisms’ respiration and facilitating the cycling of carbon and nutrients. Oxygen measurements have been interpreted to indicate that the ocean’s oxygen-deficient zones (ODZs) are expanding under global warming1,2. However, models provide an unclear picture of future ODZ change in both the near term and the long term3,4,5,6. The paleoclimate record can help explore the possible range of ODZ changes in warmer-than-modern periods. Here we use foraminifera-bound nitrogen (N) isotopes to show that water-column denitrification in the eastern tropical North Pacific was greatly reduced during the Middle Miocene Climatic Optimum (MMCO) and the Early Eocene Climatic Optimum (EECO). Because denitrification is restricted to oxygen-poor waters, our results indicate that, in these two Cenozoic periods of sustained warmth, ODZs were contracted, not expanded. ODZ contraction may have arisen from a decrease in upwelling-fuelled biological productivity in the tropical Pacific, which would have reduced oxygen demand in the subsurface. Alternatively, invigoration of deep-water ventilation by the Southern Ocean may have weakened the ocean’s ‘biological carbon pump’, which would have increased deep-ocean oxygen. The mechanism at play would have determined whether the ODZ contractions occurred in step with the warming or took centuries or millennia to develop. Thus, although our results from the Cenozoic do not necessarily apply to the near-term future, they might imply that global warming may eventually cause ODZ contraction.

Read more: https://www.nature.com/articles/s41586-022-05017-0

I’m personally surprised by this discovery. I accepted the theory that outgassing from warmer water would slightly reduce ocean oxygen levels, though given the abundance of ocean life during previous warm periods, I didn’t think it would be a problem.

Obviously it would be funny to suggest this surprise discovery is proof the oceans are cooling, and this might actually be the explanation – the sea level has dropped 6ft since the Holocene Optimum ended 6000 years ago. Maybe our modern warm period has been too brief a blip to have impacted the ocean oxygen changes wrought by our long term Holocene cooling trend.

But I accept the Princeton explanation, that we just don’t know.

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Bill Toland
September 1, 2022 11:28 pm

This sounds familiar. We don’t know what’s going on. We need more money for research so that we can fix it.

M Courtney
Reply to  Bill Toland
September 2, 2022 3:32 am

It’s OK to say “We don’t know”. It’s often true.
And asking for research funds so as we can learn is also OK.

Bill Toland
Reply to  M Courtney
September 2, 2022 5:09 am

It’s actually refreshing for scientists to admit that they don’t know. It makes a pleasant change from some climate scientists.

KcTaz
September 1, 2022 11:53 pm

“But I accept the Princeton explanation, that we just don’t know.”
Given that there are many things that we just don’t know and many more things we think we know but don’t, I find it refreshing that they admitted that. However, give it a minute and we will see lots of folks claiming it’s due to CAGW no matter how little sense that may make just because everything is due to CAGW these days. 

spangled drongo
September 2, 2022 12:10 am

Thanks Eric, and when the latest mean sea level at the best gauge for the biggest ocean in the world says it is currently an inch and three quarters LOWER than it was when the first MSL was recorded 108 years ago, maybe it is still cooling:

http://www.bom.gov.au/ntc/IDO70000/IDO70000_60370_SLD.shtml

DHR
Reply to  spangled drongo
September 2, 2022 3:17 am

Your cited data show a slight rise in MSL, not a decrease. Also, GPS gauges at Sidney and nearby show that the land level is sinking – at least recently.

spangled drongo
Reply to  DHR
September 3, 2022 12:47 am

MSL of 1.111m May 1914. First recording
MSL of 1.067m July 2022. Last recording
= 44mm lower

Also with land sinking that makes it lower still.

Peta of Newark
September 2, 2022 12:11 am

Only 2 little words, you know what they are.

We are shovelling (dust storms and ‘brown-water floods) ‘nutrition’ into the ocean (Phosphorus, Potassium, Nitrogen, Sulphur, Magnesium etc) and that is doing 2 different things to 2 diametrically opposite places
3 things really.

  1. It creates desert where those nutriments came from (farmland mostly)
  2. It creates epic overgrowth of plant-life in the water (algae blooms and stuff) and when those things die and decay (capturing Carbon as they go haha), they strip out the Oxygen
  3. It creates ill-health (mental as well as physical) among the people who are forced, because there’s nothing else, to eat the nutrient free mush (##) now being grown on the rapidly desertifying farms.

## 2 main errors going on in there:
Calories are not = Food
Quality is desirable over Quantity
3rd error being that ‘more research’ will not fix those problems but Point 3 above means that it never will.
We actually do already know all there is to know about what’s going on.

Oldseadog
September 2, 2022 1:39 am

“…..models provide an unclear picture…..”.

Stopped reading at that point.

fretslider
September 2, 2022 2:03 am

“we don’t yet know…”

Have they considered biological and chemical oxygen demand?

Gregory Woods
September 2, 2022 4:32 am

and what else about climate do we not know?

Tom Halla
September 2, 2022 7:45 am

But isn’t considering paleoclimate doubleplus ungood crimethink? As it is inconsistent with climate armageddon claims about any rise in CO2?
We must have faith in Saint Michael Mann, and not ask any embarrassing questions.

Steve Oregon
September 2, 2022 7:57 am

Science by presumption is better referred to as fantasy & fraud.
Jane Lubchenco mendaciously presumed “AGW was responsible for Oregon ocean dead zones that were new, getting larger, occurring more often and lasting longer.”
All of that was invented hogwash.
Not only did Jane have no evidence of anything relating to AGW or new about the seasonal & natural phenomenon, she and her peers used some bottled ocean water samples going back to the 50s as pretense of a historical mapping of oxygenated sea water on the Oregon coast.
As if they had a historical mapping of the dead zones going back decades.
They did not.
Flash forward and the AGW ocean dead zone myth (born out of the sloppiest of science and deceit) grew legs and ran through the media and spawned massive research grants.
As well as the Jane appointment to head NOAA.
$100s of millions have been provided for OSU and others to monitor AGW dead zones and Lubcheno’s other ocean sham “acidification”.
Nothing, has come from the expenditure but living large by those managing the funds and research lifestyle.

H. D. Hoese
Reply to  Steve Oregon
September 2, 2022 10:03 am

One might speculate that she got her information from the fish skeletons on Google Earth Ocean.

“Dissolved oxygen (O2) is essential for most ocean ecosystems, fuelling organisms’ respiration and facilitating the cycling of carbon and nutrients.” Gee, we (readers of Nature?) didn’t know that! I haven’t seen unnecessary language criticized enough except with some obviously preaching or advertising, but there is now so much verbiage that it obscures the valuables, if any.

While I can only be somewhat skeptical about overall ocean conclusions, I am certain that many inshore authors’ papers claiming decreasing oxygen haven’t done adequate homework. It goes low at night, one paper with such a claim missed an old work (1960) where it went to zero late every night. A lot depends on where and when you measure it making averages and trends difficult.

“Thus, although our results from the Cenozoic do not necessarily apply to the near-term future, they might imply that global warming may eventually cause ODZ (Oxygen-deficient zones) contraction.” Despite that probably most worthy contrary conclusion they had to end the paper with the section “Implications for future climate.” Nevertheless, I might have missed it but didn’t see what Phys.org had to say about the advocacy of what they said–“Given the complex cascade of effects associated with climatic changes, the researchers said, everything calls for efforts to limit human-driven warming.”

There is new nitrogen in the ocean, mostly in estuaries and the shelf. It has changed things, but not all negative as papers steadily prove by showing changing fisheries some from benthic to pelagic even in Chesapeake Bay. I once saw a bottom sample from off the west coast of South America where El Niño was first noticed from the guano. It was all fish bones. Phys.org needs to stick to physics.

Julian Flood
September 2, 2022 9:02 am

“Why are Ours Growing?”
Stratification. Oil and surfactant run off smooths the ocean, less stirring, lower albedo and less evaporation leads to surface warming. Nutrient run-off encourages oleaginous plankton blooms which die and produce huge smooths — I’ve seen one that was tens of thousands of square miles. More warmingmore stratification.

A modeller could check that in a couple of months given a big enough grant.

Have a look at the temperature record of the Sea of Marmora — it’s the canary in the coal mine for marine/atmosphere pollution warming.

JF

Bob
September 2, 2022 1:54 pm

Curious.

Gunga Din
September 2, 2022 2:16 pm

Hmm … Water is weird.
The colder it is, the more gases it will dissolve.
The warmer it is, the more solids it will dissolve.
The warmer it is, the less gases it will dissolve.
The colder it is, the less solids it will dissolve.

CO2 is a gas. O2 is a gas.
In CliPolSci, they seem to have stopped at that experiment 100 or so years about CO2 being a Green House Gas so CO2 controls all and therefore Man’s CO2 must be controlled.

All other real LIFE factors are ignored in Climate Political Science if they don’t support the Political “Cause”.

Ted
September 2, 2022 3:13 pm

This time is different because it’s caused by human CO2. What more does anyone need to know?

Julian Flood
September 3, 2022 1:08 am

“Why are Ours Growing?”
Stratification. Oil and surfactant run off smooths the ocean, less stirring, lower albedo and less evaporation leads to surface warming. Nutrient run-off encourages oleaginous plankton blooms which die and produce huge smooths — I’ve seen one that was tens of thousands of square miles. More warmingmore stratification.
A modeller could check that in a couple of months given a big enough grant.
Have a look at the temperature record of the Sea of Marmora — it’s the canary in the coal mine for marine/atmosphere pollution warming.
JF

September 3, 2022 2:34 pm

One factor to remember is that CO2 actually – contrary to what one might expect – boosts ventilation or oxygenation of the deep ocean. This has been shown by palaeo proxy analysis of chemical species such as uranium compounds indicating historical periods when the ocean floor was anoxic. More atmospheric CO2 correlated with less, not more deep ocean anoxia:

https://ptolemy2.wordpress.com/2020/10/14/atmospheric-co2-is-good-for-the-deep-ocean/

This is because more CO2 means more photosynthesis and thus more oxygen generated in the upper ocean to be downwelled to the ocean floor.

In warmer periods of the Palaeocene and Eocene there was more CO2 therefore less deep ocean anoxia. More CO2 because of warmer climate – not the other way around.

Of course to move that surface oxygen to the ocean floor depends on ocean circulation and the THC which is also a major factor here.

Last edited 1 month ago by Phil Salmon
Indur Goklany
September 3, 2022 6:07 pm

Is it possible that a factor at play is that higher CO2 leads to more photosynthesis which leads to more oxygen?

Reply to  Indur Goklany
September 4, 2022 6:54 am
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