There’s also this (much longer, but very helpful) science brief: oceanrep.geomar.de/id/eprint/59... which includes a nice graphic on it:

I would expect some correlation, i.e. stronger gyre = more dense water formation (os.copernicus.org/articles/21/...) = more O2 uptake

See also this paper relating O2 & gyre strength: www.nature.com/articles/s43...

Though these are about the gyre, which is related to, but not the same as, AMOC

The change in the figure is mostly spatial (eastern vs western SPNA), but certainly would expect these processes to change over time too.

I’m currently looking at that, and preliminary results indicate O2 uptake & change are strongest in 2015/16, possibly related to North Atlantic Oscillation

And as a bonus, here is a video by @scishow.bsky.social which does a great job explaining ventilation based in part on my previous work: youtu.be/rIvt4s7CX2M - though I’d now argue the whole subpolar North Atlantic is the “lung” of the ocean rather than just the Labrador Sea 🙂
15/🧵

Lastly, a big thanks to my coauthors - @aj-fassbender.bsky.social, @jdsharp.bsky.social, @dcarrollsci.bsky.social, Alison Gray, and Greg Johnson - to Sarah Battle for creating the schematic, our two reviewers, and everyone involved with @bgc-argo.bsky.social and @globaloceanbgc.bsky.social!

14/🧵

Read the paper for much more than I could fit here, including
- Actual numbers and uncertainties
- Which gas exchange parameterization we used (and why)
- All the nitty gritty calculations - also available @ github.com/jkoell
- What all this means for how we define ocean ventilation in models

13/🧵

Not at all! As shown in the schematic, the Labrador Sea is where the accumulated O2 can reach the deep ocean. Exactly how that happens still needs to be researched further - luckily Una Miller (et al) is doing just that, so stay tuned (and go to @jaimepalter.bsky.social’s talk at #OSM26!)

12/🧵

Which brings us back to our lovely schematic. Our results highlight that ventilation occurs all along the subpolar gyre pathway, in contrast to previous studies (including my own) that focused largely on the Labrador Sea for O2 uptake/ventilation

So does this mean the Lab Sea doesn’t matter?

11/🧵

To understand why, we turned to an Argo float that tracked the circulation through the SPNA.
The data shows that water is progressively modified: light water becomes SPMW, which becomes denser SPMW, which becomes LSW. The high O2 of LSW is the end result of uptake throughout this process

10/🧵

Going back to the observational data, O2 levels increase during winter in different water masses - ocean layers defined by their density - as a result of the uptake.

Surprisingly, the change is strongest in subpolar mode water (SPMW), not Labrador Sea Water (LSW), the highest O2 water mass

9/🧵

Analyzing data from an ocean model we find similar patterns, and also see that the positive oxygen uptake is balanced by a negative transport divergence - implying that the oxygen absorbed from the atmosphere is subsequently carried away by ocean currents.

8/🧵

This allowed us to estimate the air-sea exchange of oxygen for the whole SPNA; previous studies had only been able to sample at a single location.

We find that almost the entire SPNA (green box) is an annual oxygen sink, meaning O2 flows from the atmosphere into the ocean year after year

7/🧵

Which is where our study comes in - improving our understanding of how the North Atlantic is ventilated currently

To find out, we used GOBAI-O2, a data product created by @jdsharp.bsky.social with the help of an army of ocean robots that sample all over the world (@bgc-argo.bsky.social)

6/🧵

Deoxygenation is projected to further accelerate in the future, and decreased ventilation is a likely reason (doi.org/10.1038/s415...)

But we don’t fully understand when, where, or how much O2 the ocean “breathes in” now, making it difficult to accurately predict future changes

5/🧵

Oxygen levels in the ocean interior are set by the balance between this supply and oxygen demand from organisms. ⚖️

But - surprise surprise - this delicate balance is threatened by climate change. The ocean has lost 2% of its oxygen since the 1950s, with serious consequences for marine life

4/🧵

Why do we care about oxygen in the ocean? Well, because things living there need to breathe

And unlike those of us breathing air, ocean organisms can’t always rely on there being enough O2. Without sunlight for plants to grow below ~200m, ventilation is the main O2 supply for most of the ocean

3/🧵

We looked at ocean ventilation - uptake of oxygen from the atmosphere and its spreading to the rest of the globe - in the subpolar North Atlantic (SPNA), where surface and deep ocean are connected

The goal was to better understand present-day SPNA ventilation to help improve future projections
2/🧵