PP021-05
Boron Isotope Based pH Record of Last Three Decades Using the Porites Coral From the Arabian Sea
Wednesday, 9 December 2020: 19:16
Virtual
Mohd Tarique1,2, Waliur Rahaman3, Fousiya A a4, Sambuddha Misra5, Hema Achyuthan6, N Lathika1 and Meloth Thamban1, (1)National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa, India, (2)Department of Marine Geology, Mangalore University, Mangalore, India, (3)National Centre For Polar And Ocean Research, Ministry of Earth Sciences (Govt. of India), Goa, India, (4)National Centre for Sustainable Coastal Management, Anna University, Chennai, India, (5)Indian Institute of Science, Bangalore, Centre for Earth Sciences, Bangalore, India, (6)Institute of Ocean Management, Anna University, Chennai, India
Abstract:
The post-industrial atmospheric CO
2 rise has resulted decline in ocean pH, commonly known as “ocean acidification (OA)”, which has become a threat to marine calcifiers. Instrumental and proxy-based ocean pH records from the Pacific and Atlantic oceans partially demonstrate the expected long-term OA trend with large spatio-temporal variability [1, 2]. OA trend for the Indian Ocean is not known due to the absence of any pH record. Here, we provide the first sub-annually resolved pH record (1990–2013) based on boron isotope (δ
11B) measurement of
Porites corals from the Arabian Sea.
Our pH record is characterised by the absence of a long-term declining trend as expected from the ~50 ppm increase in atmospheric CO2 during the coralline growth interval; instead, it reveals a large sub- to inter-annual variability. Utilizing multi-proxies i.e. Li/Mg, Sr/Ca ratios, and δ13C from the same samples, we investigated the role of temperature and productivity on the observed pH variability. Our preliminary investigation suggests that oceanographic changes might play dominant role over other factors in modulating pH variability in the Arabian Sea. An effort will be made to deconvolute the contributions of oceanographic factors and atmospheric CO2 forcing based on the multi-proxy approach.
[1] D'Olivo et al., (2019), EPSL, 526, 115785 DOI: 10.1016/j.epsl.2019.115785
[2] Fowell et al., (2018), GRL, 45, 3228– 3237 DOI: 10.1002/2017GL076496
