Seminar by Dr Erik Kolstad, NORCE

Title: Investigating the feedbacks between the ocean and the NAO using mediation analysis

Abstract: Understanding what affects our winter weather has always been important. One of the key patterns influencing the winter climate around the North Atlantic is called the North Atlantic Oscillation (NAO). This pattern can lead to very cold or unusually warm weather and affects how much rain or snow we get. Although scientists know that ocean temperatures from earlier in the year play a role in shaping this pattern, exactly how this happens has been unclear. In our study, we used a rather simple statistical method to show how ocean temperatures in November are connected to the NAO throughout the subsequent winter. I will describe this method – mediation analysis – which has the potential to be used for many other situations where one looks for causality in the climate system. With this method, we discovered that certain processes in the atmosphere, like heat transfer from the ocean to the atmosphere, and sharp temperature differences, help explain the connection between the ocean in November and the NAO in winter. Our findings reveal a two-way interaction between the ocean and the atmosphere, showcasing a complex relationship that helps explain our winter weather.