Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Discussion papers
https://doi.org/10.5194/bg-2018-438
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-438
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Oct 2018

Research article | 15 Oct 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Assessment of paleo-ocean pH records from boron isotope ratio in the Pacific and Atlantic ocean corals: Role of anthropogenic CO2 forcing and oceanographic factors to pH variability

Mohd Tarique and Waliur Rahaman Mohd Tarique and Waliur Rahaman
  • National Centre for Polar & Ocean Research, Goa

Abstract. Boron isotopes (δ11B) records from tropical ocean corals have been used to reconstruct paleo-pH of ocean for the past several decades to few centuries which are comparable to the resolution of instrumental records. In most of the studies, attempts have been made to decipher the role of anthropogenic CO2 forcing to recent trend of ocean acidification based on δ11B derived paleo-pH records. However, such attempts in past were often hindered by limited knowledge of oceanographic factors that contributed to past pH variability and changes. In this study, we have evaluated pH records reconstructed using δ11B records from the Pacific and the Atlantic Oceans corals and investigated major forcing factors that contributed to sub annual-decadal scale pH variability and changes since the industrial era ~1850AD.

To the best of our knowledge, total eight δ11B records from the Pacific and two from the Atlantic Oceans are available in published literatures. The compilations of these records show large variability; range between 26.27–20.82‰ which corresponds to pH range 8.40–7.63 respectively. Our investigation of pH records from the Pacific ocean based on principal component analysis (PCA) reveals that atmospheric CO2 can explains maximum up to ~26% of the total pH variability during 1950–2004AD, followed by the ocean-climate oscillations (i.e. ENSO and PDO) driven oceanographic factors up to ~17%. The remaining large variability (~57%) could not be explained by above forcing factors and hence we invoke possible influence of metabolic processes of corals and/or changes in micro-environments within the reefs which are often neglected in interpreting paleo-pH records. Therefore, we highlight the need for detailed investigation in future studies to understand about the exact mechanism, processes/factors that controlled boron isotope fractionations in coral reef environments. Further, our investigation reveals that amplitude of the ENSO driven pH variability shows fivefold increase during 1980–2000AD compared to the previous three decades (1950–1980AD). This observation is consistent with the historical records of global coral bleaching events and therefore underscores role of ENSO driven environmental stress responsible for coral bleaching events. Considering model based projections of increasing frequency and amplitude of extreme ENSO events in the backdrop of recent global warming, bleaching events are likely to increase in the next decades/centuries.

Mohd Tarique and Waliur Rahaman
Interactive discussion
Status: open (until 26 Nov 2018)
Status: open (until 26 Nov 2018)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Mohd Tarique and Waliur Rahaman
Mohd Tarique and Waliur Rahaman
Viewed
Total article views: 339 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
246 90 3 339 14 1 7
  • HTML: 246
  • PDF: 90
  • XML: 3
  • Total: 339
  • Supplement: 14
  • BibTeX: 1
  • EndNote: 7
Views and downloads (calculated since 15 Oct 2018)
Cumulative views and downloads (calculated since 15 Oct 2018)
Viewed (geographical distribution)
Total article views: 339 (including HTML, PDF, and XML) Thereof 339 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited
Saved
No saved metrics found.
Discussed
No discussed metrics found.
Latest update: 14 Nov 2018
Publications Copernicus
Download
Citation
Share