I have CTD and Chlorophyll data for an upwelling location from two different years (Aug 2017 and Aug 2018). What should I be looking at to get an idea about the age of upwelled waters?
Hi Saumya,
Here are some clues with regard to your question.
Radiocarbon (14C) in dissolved inorganic carbon in the ocean can trace the age of ocean water relative to the atmosphere and provide insight into climate‐driven changes in ocean circulation since the last glaciation.
The surface waters of the modern ocean are not in 14C isotopic equilibrium with the atmosphere. A steady state balance exists between the slow invasion of atmospheric 14C into surface waters following production in the atmosphere and the aging of isolated interior water (marked by the decay of 14C over time) with the subsequent cycling of those waters back to the mixed layer. These dynamics result in an age difference between surface waters and the atmosphere termed the reservoir age.
I think you can follow the approach outlined above to determine a possible age difference between your 2017 and 2018 water samples. Evidently you will have to apply a good statistical test to determine whether a difference in reservoir age is statistically significantly different. This requires a very accurate estimate of the variability (or standard deviation) on your reservoir age measurements. Furthermore, two samples in time are not enough to elicit a trend in reservoir age I am afraid. For this type of analysis you need more sampling in function of time (years).
Lots of success.
Frank
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