{"id":374971,"date":"2025-04-13T19:34:48","date_gmt":"2025-04-13T17:34:48","guid":{"rendered":"https:\/\/climatescience.press\/?p=374971"},"modified":"2025-04-13T19:34:50","modified_gmt":"2025-04-13T17:34:50","slug":"ocean-co2-outgassing-with-temperature","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=374971","title":{"rendered":"Ocean CO2 Outgassing With Temperature"},"content":{"rendered":"\n
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From Watts Up With That?<\/a><\/p>\n\n\n\n

Guest Post by\u00a0<\/strong>Willis Eschenbach<\/a> (yes, I\u2019m still banned from X\/Twitter, see\u00a0here<\/a>).<\/p>\n\n\n\n

Over at Dr. Jennifer Marohasy\u2019s always interesting blog, she makes an interesting <\/a>claim <\/a>about ocean outgassing of CO2.<\/p>\n\n\n\n

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Picture this: it\u2019s a hot day, and you grab a soda can that\u2019s been in the sun. You crack it open\u2014psssht\u2014and CO\u2082 fizzes out, tickling your nose, maybe spraying your shirt if you\u2019re slow. It\u2019s a tiny chaos, a burst you can\u2019t control. Now imagine that fizz across the ocean\u2019s sun-warmed surface, covering 71% of Earth, bubbling CO\u2082 into the air we breathe. Wild, right? A bit mad. I reckon it\u2019s a missing piece of the climate puzzle.<\/em><\/p>\n<\/blockquote>\n\n\n\n

Now, it\u2019s undeniable that warmer ocean water contains less CO2 than colder water. As the temperature rises, the CO2 outgasses from the ocean. But that wasn\u2019t my question. After reading her post, my question was, \u201cHow much?\u201d<\/em>.<\/p>\n\n\n\n

How much increase in CO2 do we get from a 1\u00b0 increase in ocean temperature?<\/p>\n\n\n\n

My first step was to look at the Vostok ice core data. It shows that as the globe rose by ~ 5\u00b0C, the CO2 level rose by ~ 100 ppmv. This gives us a CO2 outgassing trend of ~20 ppmv per 1\u00b0C temperature rise.<\/p>\n\n\n\n

However, it\u2019s not quite that simple. More of the ocean was covered by sea ice during the glaciation, reducing the outgassing ocean area. How much? Estimates are on the order of 30 million km^2, which is about 8.2% of the current ice-free ocean. So that would drop the value to ~ 18 ppmv\/\u00b0C.<\/p>\n\n\n\n

Next, I went to my go-to AI, perplexity, which gave me the following:<\/p>\n\n\n\n

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To estimate the increase in atmospheric CO\u2082 from a 1\u00b0C rise in ocean temperatures, Henry\u2019s law and equilibrium dynamics between the ocean and atmosphere are key. Here\u2019s a synthesis of insights from relevant studies:<\/em><\/p>\n\n\n\n

\u2022 Henry\u2019s Law and Temperature Dependence<\/em><\/p>\n\n\n\n

Henry\u2019s law states that the concentration of dissolved CO\u2082 in seawater (C) is proportional to its partial pressure in the atmosphere (p): <\/em> <\/em>C = k_H * p, where(k_H) is Henry\u2019s constant, which decreases with rising temperature (reducing CO\u2082 solubility). For example, a 1\u00b0C increase reduces(k_H) by ~4%[1][6]. This shifts the equilibrium, releasing CO\u2082 from the ocean to the atmosphere.<\/em><\/p>\n\n\n\n

\u2022 Model Estimates<\/em><\/p>\n\n\n\n

1. Simplified Ocean Layer Model: <\/em> <\/em><\/p>\n\n\n\n

 <\/em>Using a 100m-deep surface layer exchanging CO\u2082 with the atmosphere, a 1\u00b0C rise increases atmospheric CO\u2082 by ~6 ppm[1]. However, this assumes limited vertical mixing and may underestimate the full ocean response. <\/em> <\/em><\/p>\n\n\n\n

   <\/em>\u2013 For deeper layers (e.g., 3800m), the same temperature rise could yield ~20 ppm[1], aligning with glacial-interglacial transitions where a 5\u00b0C warming corresponded to ~90 ppm CO\u2082 rise (~18 ppm\/\u00b0C) [1][7].<\/em><\/p>\n\n\n\n

2. Modern Context: <\/em> <\/em><\/p>\n\n\n\n

Recent studies highlight complexities like the ocean\u2019s thermal skin layer and vertical mixing. Correcting for temperature gradients between the ocean surface and sampling depth increases estimated CO\u2082 uptake by 0.8\u20130.9 PgC\/yr[2], but this focuses on current anthropogenic fluxes rather than equilibrium responses. <\/em> <\/em><\/p>\n\n\n\n

\u2022 Key Variables<\/em><\/p>\n\n\n\n

\u2013 Mixed-Layer Depth: Shallow layers (e.g., 100m) show smaller CO\u2082 releases than deeper layers[1].<\/em><\/p>\n\n\n\n

\u2013 Buffering by Carbonate Chemistry: CO\u2082 dissolution forms carbonic acid, which dissociates into ions, adding complexity beyond Henry\u2019s law[5][6]. This buffers pH changes but does not prevent long-term CO\u2082 release as temperatures rise.  <\/em><\/p>\n\n\n\n

\u2022 Synthesis<\/em><\/p>\n\n\n\n

The estimated increase ranges from 6\u201320 ppm\/\u00b0C, depending on assumptions about ocean mixing depth and timescales. The higher end (~18 ppm\/\u00b0C) aligns with paleoclimate evidence[1][7], while modern models suggest lower values due to ongoing oceanic uptake[2][3]. These estimates exclude feedbacks like biological responses or changes in ocean circulation.<\/em><\/p>\n\n\n\n

Citations:<\/em><\/p>\n\n\n\n