I’m a map person. And recently I stumbled upon this map: Global catchment drainage in relation to whole oceans.
Legend: Major endorheic basins of the world are shown in dark gray; Major endorheic lakes are shown in black; Coloured regions represent the major drainage patterns of the continents to the oceans (non-endorheic); Continental divides are indicated by dark lines.
It made me dwell upon something for the first time.
That this something was most probably already the subject of numerous treatise didn’t seem to bother me. I pondered it none the less: Might there be a significant difference in the amount of surface water draining from the land into the various oceans? And what effect does this have upon the productivity of large ‘local’ oceans?
While I know that all the oceans mix to varying degrees, what does it mean that the area of lands that drain to the Atlantic (see map, which includes all the green, yellow-green and blue areas surrounding the Atlantic (including the African, southern European and Black Sea catchments that drain into the Mediterranean; and excluding the Arctic drainage lands)) is far greater than the area of lands that drain to the Pacific (only the purple areas on the map)?
And looking at the make-up of these ocean drainage divisions I would guess, at a quick glance, that the average runoff per unit area coming from the aforementioned Atlantic draining lands is greater than than average runoff from the Pacific draining lands.
Could one say therefore that nutrient inputs (i.e. those carried off the land to the sea by the various hydrological processes) are greater in the Atlantic than in the Pacific? And given that the area of the Atlantic is smaller than the Pacific, are the effects of a greater nutrient input further concentrated, giving rise to an Atlantic ocean ecosystem that is more productive than the Pacific? Before mixing? Maybe?
One could go on to compare the size of the Indian Ocean drainage catchments (all the red on the map) to that of the area of lands that drain to the Pacific, but accurate size comparisons are needed.
Why bother?, you say. Well this little map has certainly made me see the ocean ecosystems more as products of the land that nurtures them.
planetlars 