LSG/Marginal Sea Model (MSM) Coupling Report #1

This note shows a few graphs from the coupled LSG/MSM.

Model Configuration:

The LSG model's Mediterranean Sea has been filled in, and replaced by the Marginal Sea Model. There is net flow into the marginal sea, since it is a evaporation basin; global sea-level budgets suggest that this is correctly taken care of (but I still need to do a more detailed check). For the runs shown here, the ocean model was initialized with a constant salinity of 35 ppt, so that the Mediterranean outflow water (which is of higher salinity) could be easily distinguished from the water which originally filled the basin. (The LSG model's construction is such that it would be a lot of effort to add a passive tracer, unfortunately).

Figure 1 shows the salinity 10 years after the run begins, at a depth of 700 meters (near the final outflow depth, including entrained water).

Figure 1. North Atlantic Salinity, year 10; depth=700 m.

The initial location of the outflow water is clearly evident. I should mention that "outflow water" in this context always means the water after the effects of entrainment have been added. The way I added the MSM to the LSG, only the final product water, after the entrainment process has occurred, is relevant.

The salinity at year 70 is shown in Figure 2.

Figure 2. North Atlantic Salinity, year 70; depth=700 m.

One branch of the Med Sea outflow has flowed north along the coast, almost reaching Iceland. Another, broader portion is directly filling the North Atlantic.

This pattern with two branches continues; Figure 3 shows the salinity after 110 years, when the Med Sea has infiltrated the GIN sea and begun to affect the NADW.

Figure 3. North Atlantic Salinity, year 110; depth=700 m.

The influence of the Med water on the NADW by year 150 can be seen in a east-west transect along 37.5 N, which is shown in Figure 4.

Figure 4. Salinity Transect along 37.5 N, year 150.

The NADW core, flowing South along the east coast of the U.S., shows up as a region of elevated salinity due to mixing-in of the Med water. The Med water itself is the high-salinity water mass flowing north on the eastern side of the basin.

This Med-salinified water goes on to fill up the entire world ocean. Figure 5 shows a time series of salinity at 3000 meters, with the interval between frames being 100 years.

Figure 5. Time series of salinity at 3000 meters

It is easy to see how the Med water, carried by the NADW at this depth, goes eastward around the tip of Africa, and gets advected into the Pacific basin by the ACC.

Finally, a profile of velocities into and out of the marginal sea, as calculated by the MSM, is shown in Figure 6.

Figure 6. Velocity profile at "mouth" of marginal sea

The strong, shallow flow into the marginal sea can be seen, as well as the broad outflow of water after the entrainment process has been added in. The slight "shoulder" on the inflow peak shows the inflowing water which is entrained into the descending plume.

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