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.