Main.CurrentWorkSalinitydrift History
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Changed lines 7-8 from:
-> An iceberg calving field has been made by simply scaling the pattern derived for [=HadCM3=] to match the FAMOUS water-loss - NB I didn't repeat the process by which the [=HadCM3=] field was derived using various regional components. This is included in the Summer '07 FAMOUS release. Whilst very small, salinity drift is still not zero, as the snow build up on land/ice is not constant - after 200 years running with the new iceberg field the original positive salinity drift has become a very small negative drift. In its present form the iceberg field is thus not suitable for really extended runs. It's probably inappropriate for paleoruns anyway, seeing as it's derived for modern conditions. To answer the questions in July below: snow on land is not reduced at any point, so this does "create" water in the system. And it's not really desirable to have iceberg calving match the snow accumulation rate - iceberg calving is obvious dependent on the wider ice sheet growth/dynamics that we don't have: having a constant rate is one thing, having a variable rate based on a (basically) arbitrary climate variable is just silly. It's a quick fix that can be justified for a single, stable climate state - pretending we've got an iceberg model of any sort would be ingenuous.
to:
-> An iceberg calving field has been made by simply scaling the pattern derived for [=HadCM3=] to match the FAMOUS water-loss - NB I didn't repeat the process by which the [=HadCM3=] field was derived using various regional components. This is included in the Summer '07 FAMOUS release. Whilst very small, salinity drift is still not zero, as the snow build up on land/ice is not constant - after 200 years running with the new iceberg field the original positive salinity drift has become a very small negative drift. In its present form the iceberg field is thus not suitable for really extended runs. It's probably inappropriate for paleoruns anyway, seeing as it's derived for modern conditions. To answer the questions in July below: snow on land is not reduced at any point, so this does "create" water in the system. And it's not really desirable to have iceberg calving match the snow accumulation rate - iceberg calving is obvious dependent on the wider ice sheet growth/dynamics that we don't have: having a constant rate is one thing, having a variable rate based on a (basically) arbitrary climate variable is just silly. It's a quick fix that can be justified for a single, stable climate state - pretending we've got an iceberg model of any sort would be disingenuous.
Changed lines 21-23 from:
-> For open ocean points, the water fluxes and virtual salt fluxes are accumulated every timestep. Once a year these are summed and a globally constant correction is derived. This is then applied over the course of the next year so that the long term salinity drift in the ocean matches any long term drift in the water fluxes applied (drift in water fluxes may come about from the accumulation of snow on land, for example). The correction is applied to every ocean box, not just at the surface: adtan has already run long enough that the current drift is fairly uniform with depth, and applying the correction only at the surface would result in a strong freshening of surface salinity (whilst the deep ocean still gets saltier) that impacts the MOC strength. This mod is included in the December 2006 FAMOUS (xbyvs)
to:
-> For open ocean points, the water fluxes and virtual salt fluxes are accumulated every timestep. Once a year these are summed and a globally constant correction is derived. This is then applied over the course of the next year so that the long term salinity drift in the ocean matches any long term drift in the water fluxes applied (drift in water fluxes may come about from the accumulation of snow on land, for example). The correction is applied to every ocean box, not just at the surface: adtan has already run long enough that the current drift is fairly uniform with depth, and applying the correction only at the surface would result in a strong freshening of surface salinity (whilst the deep ocean still gets saltier) that impacts the MOC strength. This mod is included in the December 2006 FAMOUS (xbyvs). For more technical details, see VfluxDriftXdbua