Interaction Between a Medicane and the Mediterranean Sea: Sea Surface Temperature Anomalies Along the Path of Medicane Daniel, the Deadliest Mediterranean Cyclone

Medicane Daniel, which formed during 4 - 12 September 2023, has stood out as the deadliest recorded storm in Mediterranean history. In this study, we investigate the role of oceanic features in contributing to the intensification of Medicane Daniel. Our findings reveal the presence of a warm core eddy (WCE), high ocean heat content (OHC), and a marine heatwave (MHW) at the location where Medicane Daniel intensified. These features were situated near the coastal region, facilitating the Medicane’s intensification close to the coast. Consequently, the Medicane did not weaken significantly after landfall, leading to severe damage along the coast of Libya. These conditions favoured the intensification of the Medicane and, owing to high moisture convergence, contributed to significant precipitation over the eddy and MHW regions. Observations further indicate that the total water column, low-level vorticity, and humidity at 850 hPa were elevated at the intensification location, reinforcing the Medicane’s intensification and associated heavy precipitation over the eddy and MHW region. Importantly, observations from the high-resolution SWOT satellite captured the WCE more accurately and in finer detail, enabling attribution of changes in biogeochemical properties, namely chlorophyll, phytoplankton, nutrients, and dissolved oxygen concentrations, to eddy-induced vertical mixing and upwelling. The biogeochemical properties tend to increase over the WCE and MHW locations due to enhanced mixing and upwelling associated with these oceanic features. Our case-study analysis suggests that under cyclone conditions, upwelling driven by Ekman pumping may play a more prominent role within WCEs in driving chlorophyll enhancement.

Key Words: Medicanes, Chlorophyll Concentration, Marine Heat Wave, SWOT observations, warm core eddy, Ekman pumping