High resolution dissolved methane data using a new response time correction technique on slow response methane sensor measurements

To improve our understanding of critical environmental processes, high resolution measurements with acceptable accuracy are essential. Unfortunately, the high spatiotemporal variability often associated with seabed seepage environments is prone to mischaracterization due to limitations in contemporary measurement techniques. This is particularly true for dissolved methane, which are often measured by labor- and time-intensive discrete water sampling and subsequent laboratory analysis. This often yields data with inadequate spatiotemporal resolution. A potential solution to this issue is using in-situ sensors in towing, profiling, mooring/observatory or glider operations. However, typical off-the-shelf sensors with adequate payload and power requirements currently lack the response time necessary for these applications. We offer a new, easy-to-implement, laboratory and field-tested post-processing tool for retrieving fast response data from commercially available methane sensors with slow response times. The tool is based on the framework of statistical inverse theory which in practice enables the user to obtain data with quantified, explicit (modeled) measurement uncertainty and at the resolution (i.e. response time) where the sensor can provide data with a respectable level of accuracy. The user needs no input besides the raw data, sensor accuracy, and response time. In our field experiment, we successfully retrieved data corresponding to a response time of 55 s using a sensor with a stated response time of 29 minutes. Being able to obtain high-resolution data from these types of sensors can considerably enhance the capacity to properly resolve the variability within methane seep sites and comprehend associated environmental processes.