Analysis of the Impact of Medicane Ianos on Sea Surface Temperature in the Ionian Sea

The Mediterranean Sea is known for extra-tropical cyclones but occasionally under certain
conditions cyclones that have tropical characteristics may be formed. These storms resemble tropical cyclones in some key features such as the presence of a storm ‘eye’,
cloud walls and high winds and can have an impact both on coastal regions and in the
ocean layer. In this work a tropical-like cyclone (also called Mediterranean hurricane or
“medicane”) that occurred in September 2020 was examined. This medicane, which was
named Ianos, began as a tropical low pressure system and intensified into a medicane
within the Ionian Sea. DINEOF (Data INterpolating Empirical Orthogonal Functions) was
used to reconstruct missing data due to cloud contamination. Satellite, reananlysis and
in-situ data were used to examine the hydrographic effects of the medicane. The
medicane led to the cooling of the SST by up to 4°C, deepening of the MLD by ~12m,
increase in Chl-a concentration by an average of 0.07 mg/m3. Average heat loss to the
atmosphere during this period was about -150 W/m2. Medicane Ianos was accompanied
by high winds and maximum gusts of up to 100 km/h around the Ionian islands making it
a Category 1 Hurricane according to the Saffir-Simpson Scale. Salinity increase in the
subsurface waters was observed following the medicane which was associated with
horizontal advection and vertical mixing leading to the weakening of the Atlantic Water
signal and the dominance of the Levantine Surface Water in this zone.