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Bieito Fernandez Castro @bfcastro.bsky.social · 28d

What supplies nutrients to the surface layer of subtropical gyres is a long standing question in oceanography
Recent work by Kate Oglethorpe shows that horizontal nutrient fluxes by mesoscale eddies are as (if not more) important than vertical fluxes:
agupubs.onlinelibrary.wiley.com/doi/10.1029/...

The Role of Mesoscale Eddy Stirring and Microscale Turbulence in Sustaining Biological Production in the Subtropical Gyres

Mesoscale eddy stirring and diapycnal mixing supply nutrients to the world ocean's subtropical gyres Mesoscale eddy stirring supply dominates over diapycnal mixing in the thermocline and plays a ...

agupubs.onlinelibrary.wiley.com

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Bieito Fernandez Castro @bfcastro.bsky.social · Jun 20

Yep you're right! But net zero is compatible (and driven) with a significant release of young physosynthetic oxygen to the atmosphere. Which we are breathing! So I think both things make sense and we should be advocating for the importance that that has

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Bieito Fernandez Castro @bfcastro.bsky.social · Jun 20

The ocean is not a net source of oxygen to the atmosphere. But... primary producers at the surface need to release a non-negligible fraction of the oxygen they produce to air in order to compensate for the upwelling of oxygen depleted waters. I think makes our both viewpoints compatible:)

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Bieito Fernandez Castro @bfcastro.bsky.social · Jun 20

There is no need to burry organic matter in the sea floor to lock carbon away from the atmosphere. Organic matter remineralised within the water column is locked in as inorganic carbon, until circulation and mixing bring it back to the surface. The same goes for oxygen, the other way round

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Bieito Fernandez Castro @bfcastro.bsky.social · Jun 20

Most of respiration happens at the surface, but a non negligible fraction of respiration (10-20%?) occurs in the ocean interior. There, oxygen is depleted from water and can't get back in straight away. Therefore, there is a net release of oxygen to air. Maybe it is 10-20%×50%=5-10%. But not zero!

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Bieito Fernandez Castro @bfcastro.bsky.social · Jun 20

I disagree on the net zero claim. The bulk of the ocean is depleted in oxygen (oxygen concentration is below atmospheric equilibrium). This is because photosynthesis happens close to the surface, where oxygen leaves to the atmosphere.

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Reposted by Bieito Fernandez Castro

Prof Alessandro Tagliabue @altagliabue.bsky.social · Jun 7

Earth system models are plagued by uncertainties in the response of microbes to climate change. We leveraged metabolic insights from genome scale models when coupled to an ocean model in this new exciting work 🌊

www.science.org/doi/full/10....

Unveiling the link between phytoplankton molecular physiology and biogeochemical cycling via genome-scale modeling

A genome-enabled ESM built on genomic data assesses physiological acclimation and biogeochemical effects through nutrient stress.

www.science.org

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Reposted by Bieito Fernandez Castro

Eos @eos.org · Jun 7

Researchers modeled the paths of 100,000 particles of water backward in time over multiple decades to learn more about the origins of Subantarctic Mode Waters.

On the Origins of Subantarctic Mode Waters - Eos

A modeling study shows how warm subtropical waters and cold Antarctic waters combine to form an Indo-Pacific water mass that plays a key role in Earth’s climate.

eos.org

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Bieito Fernandez Castro @bfcastro.bsky.social · Jun 2

Thanks @aguadvances.bsky.social and @eos.org for sharing our work on the sources and formation process of sub-Antarctic Mode Waters!

AGU Advances @aguadvances.bsky.social · Jun 2

Thanks for spotlighting this great research @eos.org!

You can read the full #OpenAccess article by Fernández Castro et al. for free: doi.org/10.1029/2024...

#AGUPubs #SDG13 #ClimateAction #CHOW2025 #Oceans #OceanScience

Eos @eos.org · Jun 2

What goes into the Subantarctic Mode Waters? New @aguadvances.bsky.social research investigates. eos.org/research-spo...

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 28

@aguadvances.bsky.social

Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[7/7] Our results shed new light on the intricate nature of SAMWs, helping to predict and understand their role in slowing down future climate change.

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[6/7] Subtropical source waters release heat into the atmosphere, whilst Antarctic waters absorb heat. Because of their different relative contribution to Indian and Pacific SAMWs, these SAMW pools play a different role in the climate system, as sources and sinks of atmospheric heat, respectively.

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[5/7] Subtropical waters are the main precursor of Indian Ocean SAMWs (70%) but contribute a smaller amount (<40%) to Pacific SAMWs, which are mainly sourced from the upwelled CDW.

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[4/7] We found that both subtropical and Antarctic sources contribute to SAMW formation and strong inter‐basin contrasts in their contributions, between the Indian and Pacific SAMW pools.

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[3/7] We performed a flow-tracking experiment with a Southern Ocean model (B-SOSE) to address a long standing question about SAMWs: the extent to which they originate from southward‐flowing subtropical waters vs northward‐flowing Antarctic waters sourced by Circumpolar Deep Water (CDW) upwelling.

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[2/7] Sub-Antarctic Mode Waters (SAMWs) form in the Southern Ocean, north of the Antarctic Circumpolar Current. These water masses are critical for the climate system, absorbing -and holding away from the atmosphere- vast amounts of anthropogenic heat and carbon dioxide.

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Bieito Fernandez Castro @bfcastro.bsky.social · Apr 19

[1/7] Check our latest paper investigating the sources, pathways and drivers leading to the formation of Sub-Antarctic Mode Waters!

agupubs.onlinelibrary.wiley.com/doi/epdf/10....

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Reposted by Bieito Fernandez Castro

Fatima Pereira @fatimacpereira.bsky.social · Mar 27

📣 Exciting opportunity! We're hiring a #postdoctoral fellow in #gutmicrobiome research to explore the activity and function of the gut microbiome in situ and its regulation by the immune system.🦠🔬

Post based at @sotonbiosciences.bsky.social

Apply here 👇
jobs.soton.ac.uk/Vacancy.aspx...

Job Opportunity at the University of Southampton: Research Fellow (Postdoctoral) in Microbiology/Microbiome

Applications are invited for a Postdoctoral Research Fellow position in the Gut Microbiome Group, School of Biological Sciences at the University of Southampton. The University of Southampton is a wor...

jobs.soton.ac.uk

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Bieito Fernandez Castro @bfcastro.bsky.social · Mar 27

About ten days left for this job! Don't miss the chance!

Bieito Fernandez Castro @bfcastro.bsky.social · Mar 10

WE ARE HIRING. Interested in ocean mixing? Come work with us in the ARIA-funded POLEMIX project to create and deploy a float-based mixing observing system in the subpolar North Atlantic. Applications here: jobs.soton.ac.uk/Vacancy.aspx...
@sotonoceanearth.bsky.social @noc.ac.uk

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Reposted by Bieito Fernandez Castro

Bjerknes Center for Climate Research (BCCR) @bjerknes.uib.no · Mar 18

The Greenland Sea is undergoing dramatic changes due to climate change, which has altered deep water production in the Northern Hemisphere. This is not just a regional issue—it has global consequences, especially for ocean circulation and carbon absorption.🧪🌊

Dramatic Changes in the Greenland Sea

Due to climate change, deep water production has changed fundamentally in the Northern Hemisphere. This has major consequences for ocean circulation and…

bjerknes.uib.no

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Bieito Fernandez Castro @bfcastro.bsky.social · Mar 10

WE ARE HIRING. Interested in ocean mixing? Come work with us in the ARIA-funded POLEMIX project to create and deploy a float-based mixing observing system in the subpolar North Atlantic. Applications here: jobs.soton.ac.uk/Vacancy.aspx...
@sotonoceanearth.bsky.social @noc.ac.uk

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Reposted by Bieito Fernandez Castro

JGR: Oceans @jgroceans.bsky.social · Jan 8

Fernández Castro et al. (2024) find that mesoscale eddies play a dominant role in mixing heat and salt in the North Atlantic, helping us to better understand the Atlantic Meridional Overturning Circulation and its future behavior.

🔗 doi.org/10.1029/2023...

#AGUPubs

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Bieito Fernandez Castro @bfcastro.bsky.social · Feb 18

Great to have you onboard @gaelforget.net!

Bieito Fernandez Castro @bfcastro.bsky.social · Feb 17

POLEMIX will deploy a mixing observing system in the North Atlantic and feed the observations into ocean models to disentangle the fate of freshwater and its impacts on dense water formation. Hiring soon! @sotonoceanearth.bsky.social @nocmarinephys.bsky.social @imev-mer.fr @mitpress.bsky.social

University of Southampton @unisouthampton.bsky.social · Feb 17

How close are we to a dangerous North Atlantic tipping point?

We’ve received £5m from @aria-research.bsky.social to find out by collecting data on ocean mixing.

Read more 👉 brnw.ch/21wQKkT

A quote graphic that reads the following: "If ocean mixing weakens, the North Atlantic Subpolar Gyre could slow down or even collapse, triggering disruptions in weather, sea level, and global ocean circulation.

The UK and northern Europe could experience much harsher winters, while the East coast of the USA could see dramatic sea level rises."

Doctor Bieito Fernandez Castro

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Reposted by Bieito Fernandez Castro

Prof Michael Meredith 🌊🧪🥼❄️ @oceanandice.bsky.social · Feb 15

Sea ice in the Arctic and around Antarctica cool our climate, drive ocean circulation across the planet, and provide a unique habitat for polar ecosystems.

Sea ice amounts have now fallen to their lowest since we started measuring them. This is not good.

🌊🥼❄️🧪

www.bbc.co.uk/news/article...

World's sea-ice falls to record low

The world's frozen oceans keep the planet cool, but they currently have less ice than ever recorded before.

www.bbc.co.uk

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