Presentations

Abstract

In June 2023, record-breaking sea surface temperatures have been recorded in the North Atlantic Ocean. At the same time, large negative wind speed anomalies were observed in the same region (Copernicus Climate Change Service/ECMWF, 2023). At RWE, we are interested in understanding whether we can see a correlation between the sea surface temperature and the wind speed at a local level at the locations where we operate offshore wind farms. Additionally, we want to understand whether CMIP6 climate projections agree with the reanalysis data in order to assess the reliability of CMIP6 long-term wind speed projections. We use reanalysis data across ten wind farm locations to evaluate the trend of wind speed and sea surface temperature over the past 25 years. Firstly, we compute the annual anomalies of the variables using 2000-2024 as reference period. We then assess the significance of the trend using the Mann-Kendall test. Lastly, we check the correlation between the wind speed and the sea surface temperature anomalies at an annual, monthly, and seasonal scale. We use data from statistically downscaled CMIP6 climate projections with the SSP2-4.5. scenario at two locations to understand whether the predictions coincide with the extreme sea surface temperatures. We also use data from non-downscaled CMIP6 climate projections with the same scenario to assess the wind speed projections across ten sites. From the reanalysis data, we find that the sea surface temperature is increasing significantly at eight out of ten sites according to the Mann-Kendall test. The other two sites still show a clear increasing trend. The wind speed data shows a slightly decreasing trend; however, the Mann-Kendall test reveals that none are statistically significant. The climate projections show a steep increase in sea surface temperature over the past twenty-five years at the two investigated locations, which coincides with the trend shown in the reanalysis. They furthermore predict a continuous increase in sea surface temperature over the next 25 years. The CMIP6 wind speed data shows that at none of the ten sites a significant reduction occurs. Investigating the monthly and annual anomalies from the reanalysis data, we cannot observe any correlation between the two variables on either time scale. When considering seasonal anomalies instead, we see a moderate direct relationship between the wind speed and the sea surface temperature during the winter months. During summer, we observe a weak indirect correlation. In conclusion, both reanalysis and CMIP6 data show a clear, statistically significant increase in sea surface temperature across offshore locations. We do not observe a statistically significant trend for the wind speed neither in the reanalysis nor CMIP6 data. Lastly, we conclude that the correlation between the sea surface temperature and the wind speed is lower at a local level than what is observed on a global level.