In just over 20 years, the northward shift of the subtropical jet stream - a high-altitude airflow - caused by climate change has reduced primary production in the northwestern Mediterranean by about 40%. This marked reduction - the highest ever described - affects the base of the marine food web and could significantly impact living resources, ecosystem health and marine dynamics in this region of the Mediterranean.
This is one of the main conclusions of an article published in the journal Progress in Oceanography , whose main authors are Julia Crespín and Miquel Canals, from the Faculty of Earth Sciences at the University of Barcelona, and Jordi Solé, from the Institute of Marine Sciences (ICM-CSIC) in Barcelona and the Centre for Ecological Research. Experts Miquel Canals and Jordi Solé are director and member, respectively, of the UB Chair on Sustainable Blue Economy.
Primary production in the oceans consists of the synthesis of organic matter by photosynthetic organisms (phytoplankton), which capture carbon dioxide (CO2) from the atmosphere and release oxygen (O2). The effect of the persistent displacement of the jet stream on primary production could affect fisheries and local and regional economies in the medium to long term. Reduced primary production can also alter the ocean's carbon cycle - less phytoplankton means less CO2 uptake by the ocean - and this could accentuate the effects of climate change.
This study is pioneering in establishing a systematic link between the northward shift of the subtropical jet stream and the decline in marine primary production. Apart from the biological impact, the authors warn that the modification of wind patterns could also alter the surface and subsurface temperature of marine waters in the medium and long term, among other parameters, and significantly change the oceanographic dynamics of the northwestern Mediterranean.
Fast air currents circulating at high altitude
The subtropical jet stream is a high-altitude airflow that transports cold and heat at high speed, regulates the regional climate and modulates the position and intensity of surface winds, especially those of the northern quadrant, such as the tramontane and the mistral. Due to climate change, this current has progressively shifted northward, causing atmospheric patterns to change in the northwestern Mediterranean.
