Naked Science Forum

Life Sciences => Marine Science => Topic started by: thedoc on 18/05/2013 22:30:02

Title: Is the Mediterranean getting saltier?
Post by: thedoc on 18/05/2013 22:30:02

Alan Alderson  asked the Naked Scientists:
   
Thanks for a great podcast, living on a boat and sailing around europe it is a great to be able to listen to the show (http://www.thenakedscientists.com/HTML/podcasts/).

I recently sailed into Gibraltar and discovered that there is a constant flow of water from the Atlantic into the Mediterranean. I belive this is to replace the water lost by evaporation in the Med. If so doea this mean that the Med is getting saltier and saltier. And if so when will it become to saline to support marine life.

What do you think?

Title: Re: Is the Mediterranean getting saltier?
Post by: eddwilson on 18/05/2013 21:42:31

Mediterranean Sea becomes Dead Sea?

Title: Re: Is the Mediterranean getting saltier?
Post by: Lmnre on 19/05/2013 04:45:24

As Alan noticed, surface water constantly flows from the Atlantic Ocean to Mediterranean Sea, and for two reasons: #1 – water evaporates from the Med at a faster rate than from the Atlantic, #2 – a flow of saltier water flows from the Mediterranean Sea into the Atlantic along the bottom of the strait. As the water evaporates from the Med, which acts as a huge, relatively shallow evaporation pan, the saltier/heavier water sinks and eventually makes its way to the Atlantic.
(https://www.noc.soton.ac.uk/o4s/euroargo/img/med_outfl_sill.png)

In the map below, we see the salinity of the water leaving the Med at 1,000 meters, which affects the Atlantic Ocean all the way to America. This is known as the "Mediterranean salt tongue (http://scholar.google.com/scholar?hl=en&q=%22Mediterranean+salt+tongue%22&btnG=&as_sdt=1%2C22&as_sdtp=)". Along the edges of the tongue, huge pieces of it break away, which scientists call "meddies", which also make for interesting reading.

(https://www.noc.soton.ac.uk/o4s/euroargo/img/medoutflow_mercator_20090819sal.png)

Title: Re: Is the Mediterranean getting saltier?
Post by: chris on 19/05/2013 12:05:46

That's fascinating; I did not know any of that; thanks for sharing it.

Chris

Title: Re: Is the Mediterranean getting saltier?
Post by: evan_au on 20/05/2013 12:49:50

During the second world war, submarines used these currents to move into and out of the Mediterranean without their engine noise giving them away.

There are large salt deposits on the floor of the Mediterranean, suggesting that at some time in the past, the Mediterranean did actually dry up (a really dead sea). Additional evidence comes from the fact that the Nile valley has a deep gorge cut into the rock (and now filled with silt).

See: https://en.wikipedia.org/wiki/Messinian_Salinity_Crisis