CSIR NET June 2016 Q61: Physical Oceanography
Antarctic Bottom Water (AABW) is the coldest, densest, most saline-in-effect water mass that fills the deep ocean basins and drives the deep limb of the global thermohaline (meridional overturning) circulation.
AABW forms mainly around Antarctica (e.g., Weddell and Ross Seas) through brine rejection during sea-ice formation, sinks to abyssal depths, and spreads northward into all major ocean basins. Its climatic importance lies in absorbing and redistributing heat within the deep ocean as part of the global overturning circulation, acting as a major heat sink/transporter that modulates global climate over long timescales. Option 3 is correct.
1) Incorrect — AABW does not primarily control surface wind patterns. 2) Incorrect — it is not principally a nutrient source in this specific climatic-role framing. 3) Correct — heat absorption/transfer via deep circulation is its key climatic role. 4) Incorrect — sea-level regulation is not its defining function.