Figure 3 .Interannual time series (2006–2099) of 0–1000 m sea water (a) potential temperature (ºC) and (c) salinity (psu). The yearly means of (b) potential temperature (ºC) and (d) salinity (psu) computed for the layers 0–200 m (blue), 200–600 m (red), 600–1000 m (black). (e) The stratification index at 0-1000 m (blue). All-time series were simulated by ROM model under the RCP8.5 scenario for winter months (December-January-February-March, DJFM) in the GoL area. The gray bars correspond to DWF episodes (MLDmax>1000 m depth).
The time evolution of mean winter salinities (Figure 3d) shows a different behavior throughout the water column, showing a slightly freshening trend in MAW and a notable salinization in LIW and the 600-1000 m layer (Table S2).
The yearly SI at 1000 m depth shows values close to minimum values during the projected DWF events (Figure 3e), which suggests a weaker stratification of the water column. Until 2040s the SI does not show any significant trend. However, from 2040 the SI displays an upward trend (0.02 m2s-2y-1) reaching values up to 1.9 m2s-2 at the end of the 21st century. Therefore, the climate change signal introduced by RCP8.5 leads to a higher stratification of the water column which may hamper the formation of deep waters.
3.4 Fluxes at Gibrarltar Strait
The simulated water, heat and salt exchange flows through the Strait of Gibraltar are summarized in Table 1. The water outflow in Gibraltar during 2070-2099 (period without DWF episodes) experiences a decrease of 0.04 Sv in comparison with 2006-2041 (period with DWF events), while the net water flow increases by 0.02 Sv. The heat outflux increases 2.6·1010 Wyr-1 throughout the 2006-2099 period; thus, the Mediterranean Outflow (MO) becomes warmer toward the end of the century: the mean temperature of MO during 2006-2041 is 13.5ºC while for the 2070-2099 is 15.2ºC. Until 2041 the MO temperature does not present any significant change. However, during the 2041-2099 period the trend of MO temperature displays a sharp increase (0.034ºCyr-1, see supplementary: Figure S1).
Table 1. Mean water, heat and salt exchange fluxes, temperature and salinity of inflow and outflow waters at Gibraltar Strait for 2006-2041 and 2070-2099 periods simulated by ROM model under the RCP8.5 scenario. Trends computed from yearly means during 2006-2099. For the net transport calculation, positive values were assigned to inflows and negative to outflows.