Subantarctic Mode Water

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Subantarctic mode water (SAMW) is an important water mass in the earth's oceans. It is formed near the Subantarctic Front on the northern flank of the Antarctic Circumpolar Current. The surface density of Subantarctic Mode Water ranges between about 1026.0 and 1027.0 kg/m³ and the core of this water mass is often identified as a region of particularly low stratification.

Another important facet of SAMW is that silicate (an important nutrient for diatoms) is relatively depleted relative to nitrate. This depletion can be tracked over much of the globe, suggesting that SAMW helps set the blend of nutrients delivered to low-latitude ocean ecosystems, and thus determines the balance of species within these ecosystems.

Salinity (colors) and temperature (contours) at 50E, illustrating the low stratification layer associated with the Subantarctic Mode Water at this longitude.

Salinity (colors) and temperature (contours) at 170W, showing that the SAMW is much closer in temperature to the salinity minimum associated with the Antarctic Intermediate Water.

[edit] References

• Sarmiento, J. L., N. Gruber. M. Brzezinski, and J. P. Dunne, 2004: High-latitude controls of thermocline nutrients and low latitude biological productivity. Nature, 427, 56-60.
• Morris, M., H. Neil, B. Stanton, Subantarctic Mode Water: the ocean's memory, National Institute of Water and Atmospheric Research (New Zealand).