My research focuses on the development of autonomous chemical sensors for applications in aquatic (marine and freshwater) chemistry. One of our primary goals is to further our understanding of CO2’s sources and sinks within the world's oceans. Our research has resulted in the development of autonomous CO2 and pH sensors (the Submersible Autonomous Moored Instruments or SAMIs), a technology that won the 2015 Ocean Health XPRIZE.  By deploying the SAMI sensors on ocean moorings and other unmanned platforms, we have determined to what extent processes such as photosynthesis and air-sea gas exchange control CO2 variability.  These results will help develop models to predict the effects of global warming and ocean acidification (the decrease in ocean pH caused by anthropogenic CO2). Our recent field work has primarily focused on the processes that control CO2 in both freshwater (rivers and lakes) and marine environments. Our current field efforts are focused on the Arctic Ocean, where we have found that sea surface CO2 levels are increasing as ice cover diminishes, the first clear evidence that warming in the Arctic is altering the Arctic Ocean carbon cycle. Closer to home, we are also working closely with other aquatic scientists studying the biogeochemical cycling in local and regional rivers.