Seasonal cycle of surface ocean pCO2 and pH in the northern Indian Ocean and their controlling factors

Variability in Sea Surface pCO2 and Controlling Factors in the Bay of Bengal Based on buoy Observations at 15°N, 90°E

“…This dominant positive contribution to the mean seasonal pCO 2sea variability in the pre‐monsoon season and negative contribution in the post‐monsoon and northeast monsoon seasons is consistent with a previous modeling study in the BoB (Joshi and Warrior., 2022). Our results are in agreement with the results of previous studies (Boehme et al., 1998; Chakraborty et al., 2021; Sabine & Key, 1998; Xu et al., 2016; Xue et al., 2016) that reported that temperature is the largest contributor to pCO 2sea variability in open oceans, marginal seas and coastal waters.…”

“…It also receives a high influx of freshwater from rivers and precipitation (Sengupta et al., 2006; Sridevi and Sarma., 2021). This high freshwater influx and the seasonally reversal monsoon winds affect the physical characteristics and consequently the carbonate dynamics (Chakraborty et al., 2021; Joshi et al., 2021). This leads to high spatial and temporal variabilities in sea surface salinity (SSS) (Joshi et al., 2021) and brings in nutrients which leads to challenges in modeling carbonate system parameters [pCO 2sea , dissolved inorganic carbon (DIC), total alkalinity (TA), and pH] for the bay (Joshi et al., 2020; Sarma et al., 2013; Sridevi and Sarma, 2021; Valsala & Maksyutov, 2010).…”

“…Both observation and model based studies have shown low pCO 2sea in the northeastern BoB and high pCO 2sea in the southern region (Joshi & Warrior, 2022; Joshi et al., 2021; Sarma et al., 2018). Significant temporal variations of pCO 2sea with high values during the southwest monsoon and low values during the northeast monsoon season were observed (Chakraborty et al., 2021; Joshi & Warrior, 2022).…”

“…In general, the drivers of pCO 2sea variability are attributed to the changes in temperature, DIC, TA, and salinity, and the mechanisms can be grouped by thermal effect, water flux, biological effect, mixing effect, air‐sea gas exchange effect and calcium carbonate production/dissociation (Boehme et al., 1998; Chakraborty et al., 2018, 2021; Joshi & Warrior, 2022; Sarma et al., 2018, 2019). A modeling study suggested that temperature and DIC are the dominant drivers of pCO 2sea in most areas of the BoB, while salinity plays a dominant role in the northern region (Chakraborty et al., 2021). A recent modeling study revealed that mixing and biological activity effects dominate the spatial variability of pCO 2sea in the BoB (Joshi & Warrior, 2022).…”

Large salinity gradient and diagenetic changes in the northern Indian Ocean dominate the stable oxygen isotopic variation in Globigerinoides ruber

“…The pH of the seawater has also been identified as a factor affecting the stable oxygen isotopic composition of planktic foraminifera (Bijma et al, 1999). However, as argued by Mulitza et al, (2003), the limited modern surface seawater pH variability (Chakraborty et al, 2021) and its close dependence on temperature implies that the pH contribution to δ 18 Oruber is well within the error associated with the measurements.…”