We also have a
gallery where people have each chosen colors for heights
and depths in their own way;
you too can explore and color this world topography dataset.
Temperature and salinity together essentially determine the density of water, and thus how it moves about. rhoa is the density minus one (the density of water is about 1). The pressure increases with depth because of the weight of the water above: the increase in pressure tends to heat the water. The potential temperature theta compensates for those pressure-caused temperature changes to create an adiabatic tracer.
The steady state distributions of SIO2 (silicate), NO3 (nitrate), PO4 (phosphate), and O2 (oxygen) in the global ocean are controlled by a balance between dynamics and biological cycling. Due to photosynthesis in the ocean's euphotic (or sunlit) zone, the nutrients SIO2, NO3, and PO4 are stripped from surface waters on a timescale of months. Thus for most of the ocean the concentrations of these nutrients are much lower than they are at a depth of 500 meters. However, there are regions of the world ocean such as the Equatorial Pacific and the Southern Ocean where the vertical exchange of water between the surface and subsurface (>150 meters) occurs quickly enough to maintain a local maximum in surface nutrient concentrations.
Because O2 (dissolved oxygen) is produced during photosynthesis in the surface ocean (and consumed during respiration below the euphotic zone), it typically has lower concentrations in the subsurface waters than it does in the surface layer. Thus changes in the O2 content of a water parcel will tend to be inversely related to changes in nutrients.
Unlike the nutrients SIO2, NO3, and PO4, O2 exists in a gas phase and is thus exchanged between the atmosphere and the ocean. The saturation concentration of oxygen, or O2SAT, is primarily controlled by temperature. Surface water is usually quite close to saturation, so that at the sea surface O2 is within ten percent of O2SAT. For water parcels which sink from the surface layer and are away from sunlight, their O2 level tends to decrease in time as their nutrient levels increase due to respiration. The difference between O2SAT and O2 for a given water parcel is referred to as AOU (apparent oxygen utilization).
Let us know what you find in the Introduction to Climate Data Discussion. Or explore the other datasets in the Data Library.
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