4 ms·

Would probably only need 1 dam at Gibraltar. I wonder if the Mediterranean has a net info or outflow of water?

Shivetya 9y ago
I was always under the impression that evaporation would have threatened its existence if not for the in flow from the Atlantic
- twic 9y ago
  On average, the Mediterranean basin shows an excess of evaporation over freshwater inputs and a heat loss through air-sea interaction. It has an overall freshwater deficit, as the loss to the atmosphere by evaporation is larger than the gains by precipitation and runoff from the main rivers and input from the Black Sea. The total heat budget is negative, that is, the Mediterranean Sea loses more energy than it gains. These losses of freshwater and heat are compensated by the two-layer exchange at the Strait of Gibraltar comprising a relatively warm and fresh (15.4°C, 36.2 psu) upper water inflow and a relatively cooler and saltier (13°C, 38.4 psu) outflow to the Atlantic (Bryden et al. 1994; Tsimplis and Bryden 2000). On long timescales, the losses of freshwater and heat from the surface are compensated and the net salt flux is close to zero. https://link.springer.com/article/10.1007/s00382-011-1012-6 https://link.springer.com/article/10.1007/s00382-011-1012-6
jcranmer 9y ago
Net outflow, hence the Messinian Salinity Crises that happened whenever the outflow at Gibraltar was blocked.
- BatFastard 9y ago
  After looking at the Messinian Salinity Crises it tells me that without water from the Atlantic the Mediterranean would dry up. Therefore there is a net inflow into the Mediterranean, right?
pmontra 9y ago
As others have pointed out the Mediterranean Sea loses water and needs an inflow to compensate. In the case of a dam at Gibraltar it should be easy to let some water in. I wonder if we are able to build such a gigantic dam even if we wanted to. We probably need another one at Suez. According to Google Maps the elevation of the channel is always less than 100 m, which is the worst case figure for sea rise if all the ice of the world melts. Water would come in from the Red Sea. Btw, not all terrains are suitable for building dams.
- BatFastard 9y ago
  There are already locks on the Suez I believe. I would think that the Rock of Gibraltar would give the damn a decent base rock formation underneath, but you have a good point.
  - AnimalMuppet 9y ago
    No, the Suez Canal does not have locks.
  - pmontra 9y ago
    No locks. You can check at https://www.google.com/maps/@31.1497898,32.3699699,12z/data=!3m1!1e3 https://www.google.com/maps/@31.1497898,32.3699699,12z/data=... Furthermore all the area of the channel is low elevation. It will go under water when the sea level raises. Ships will just sail over it.
detritus 9y ago
Having spent much of my youth waking up and staring across the Straits every day, I question your use of 'only' in this thought. They may 'only' be 12 or so miles across, but the amount of concrete and fill that would be needed to dam the straits would dwarf anything even the Chinese could manage up with for another couple of hundred years, I imagine. This idea looks a lot more plausible on paper than it would in person.

I was always under the impression that evaporation would have threatened its existence if not for the in flow from the Atlantic

twic 9y ago
On average, the Mediterranean basin shows an excess of evaporation over freshwater inputs and a heat loss through air-sea interaction. It has an overall freshwater deficit, as the loss to the atmosphere by evaporation is larger than the gains by precipitation and runoff from the main rivers and input from the Black Sea. The total heat budget is negative, that is, the Mediterranean Sea loses more energy than it gains. These losses of freshwater and heat are compensated by the two-layer exchange at the Strait of Gibraltar comprising a relatively warm and fresh (15.4°C, 36.2 psu) upper water inflow and a relatively cooler and saltier (13°C, 38.4 psu) outflow to the Atlantic (Bryden et al. 1994; Tsimplis and Bryden 2000). On long timescales, the losses of freshwater and heat from the surface are compensated and the net salt flux is close to zero. https://link.springer.com/article/10.1007/s00382-011-1012-6 https://link.springer.com/article/10.1007/s00382-011-1012-6

jcranmer 9y ago

Net outflow, hence the Messinian Salinity Crises that happened whenever the outflow at Gibraltar was blocked.

BatFastard 9y ago
After looking at the Messinian Salinity Crises it tells me that without water from the Atlantic the Mediterranean would dry up. Therefore there is a net inflow into the Mediterranean, right?

pmontra 9y ago

As others have pointed out the Mediterranean Sea loses water and needs an inflow to compensate. In the case of a dam at Gibraltar it should be easy to let some water in. I wonder if we are able to build such a gigantic dam even if we wanted to. We probably need another one at Suez. According to Google Maps the elevation of the channel is always less than 100 m, which is the worst case figure for sea rise if all the ice of the world melts. Water would come in from the Red Sea. Btw, not all terrains are suitable for building dams.

BatFastard 9y ago
There are already locks on the Suez I believe. I would think that the Rock of Gibraltar would give the damn a decent base rock formation underneath, but you have a good point.
- AnimalMuppet 9y ago
  No, the Suez Canal does not have locks.
- pmontra 9y ago
  No locks. You can check at https://www.google.com/maps/@31.1497898,32.3699699,12z/data=!3m1!1e3 https://www.google.com/maps/@31.1497898,32.3699699,12z/data=... Furthermore all the area of the channel is low elevation. It will go under water when the sea level raises. Ships will just sail over it.

detritus 9y ago

Having spent much of my youth waking up and staring across the Straits every day, I question your use of 'only' in this thought. They may 'only' be 12 or so miles across, but the amount of concrete and fill that would be needed to dam the straits would dwarf anything even the Chinese could manage up with for another couple of hundred years, I imagine. This idea looks a lot more plausible on paper than it would in person.