Preprints
https://doi.org/10.5194/egusphere-2026-657
https://doi.org/10.5194/egusphere-2026-657
06 Feb 2026
 | 06 Feb 2026

Understanding the resilient carbon cycle response to the 2014–2015 Blob event in the Gulf of Alaska using a regional ocean biogeochemical model

Yumi Abe, Takamitsu Ito, Amanda H. V. Timmerman, Christopher T. Reinhard, and Joseph P. Montoya

Abstract. Marine heatwaves (MHWs), characterized by anomalously high sea surface temperatures, are occurring with increasing frequency and intensity, profoundly impacting ocean circulation, biogeochemistry, and marine ecosystems. The MHW known as the Blob, which persisted in the subarctic NE Pacific from 2014 to 2015, significantly affected surrounding ecosystems. Warming-induced solubility reduction is expected to raise the partial pressure of carbon dioxide (pCO2) in the surface water, causing outgassing of CO2 to the atmosphere. Outgassing of CO2 is another source of atmospheric CO2 in addition to anthropogenic fossil fuel burning. However, moored observations at Ocean Station Papa (OSP; 145° W, 50° N) shows a moderate decrease in oceanic pCO2 during the Blob, resisting the warming-induced outgassing of CO2. This response is opposite of what is expected from warming alone, and instead has been attributed to reductions in dissolved inorganic carbon (DIC), although the mechanisms driving this reduction have remained unclear. We employed a regional model that accurately reproduces the temporal variability of oceanic pCO2 at OSP to investigate the cause of decrease pCO2 during the Blob. The analysis of model outputs indicates that the observed oceanic pCO2 decline resulted from the offset between warming-induced solubility reduction (increasing pCO2) and weakened physical transport of DIC (decreasing pCO2), with the latter dominating. Both horizontal and vertical transports played important roles. The near-surface carbon budget over the broad region was primarily driven by changes in the vertical transport. The decrease in DIC during the Blob resulted from the suppression of upwelling of DIC-rich subsurface waters in the winter of 2013. In this period, the horizontal transport also contributed substantially to DIC reduction. In particular, at OSP, the effect of the horizontal transport was comparable to that of the vertical transport, reflecting the northward advection of low-DIC water masses. These findings indicate that changes in physical circulation were the primary driver of the moderately enhanced CO2 uptake observed during the Blob. This study provides a critical insight into the complexity of biogeochemical response to extreme warming events and underscores the importance of resolving physical transport processes in assessing oceanic carbon uptake during MHWs.

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Journal article(s) based on this preprint

12 Jun 2026
Understanding the resilient carbon cycle response to the 2014–2015 Blob event in the Gulf of Alaska using a regional ocean biogeochemical model
Yumi Abe, Takamitsu Ito, Amanda H. V. Timmerman, Christopher T. Reinhard, and Joseph P. Montoya
Biogeosciences, 23, 3871–3885, https://doi.org/10.5194/bg-23-3871-2026,https://doi.org/10.5194/bg-23-3871-2026, 2026
Short summary
Yumi Abe, Takamitsu Ito, Amanda H. V. Timmerman, Christopher T. Reinhard, and Joseph P. Montoya

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2026-657', Anonymous Referee #1, 21 Feb 2026
  • RC2: 'Comment on egusphere-2026-657', Anonymous Referee #2, 05 Mar 2026
  • RC3: 'Comment on egusphere-2026-657', Anonymous Referee #3, 25 Mar 2026

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2026-657', Anonymous Referee #1, 21 Feb 2026
  • RC2: 'Comment on egusphere-2026-657', Anonymous Referee #2, 05 Mar 2026
  • RC3: 'Comment on egusphere-2026-657', Anonymous Referee #3, 25 Mar 2026

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload
ED: Publish subject to minor revisions (review by editor) (20 Apr 2026) by Emilio Marañón
AR by Yumi Abe on behalf of the Authors (12 May 2026)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (15 May 2026) by Emilio Marañón
AR by Yumi Abe on behalf of the Authors (25 May 2026)

Journal article(s) based on this preprint

12 Jun 2026
Understanding the resilient carbon cycle response to the 2014–2015 Blob event in the Gulf of Alaska using a regional ocean biogeochemical model
Yumi Abe, Takamitsu Ito, Amanda H. V. Timmerman, Christopher T. Reinhard, and Joseph P. Montoya
Biogeosciences, 23, 3871–3885, https://doi.org/10.5194/bg-23-3871-2026,https://doi.org/10.5194/bg-23-3871-2026, 2026
Short summary
Yumi Abe, Takamitsu Ito, Amanda H. V. Timmerman, Christopher T. Reinhard, and Joseph P. Montoya
Yumi Abe, Takamitsu Ito, Amanda H. V. Timmerman, Christopher T. Reinhard, and Joseph P. Montoya

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Short summary
Marine heatwaves are defined by periods of unusually high sea temperature. Although warmer seawater usually reduces the ocean’s ability to absorb carbon dioxide, observations in the Gulf of Alaska showed a surprising drop in carbon dioxide during the 2014–2015 “Blob” heatwave. Using an ocean biogeochemical model, we found that this decline resulted from reduced dissolved inorganic carbon caused by weakened physical supply in winter 2013, just before the Blob began.
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