1. Would Pédelaborde approve of Curry et al.'s explanation for the cause of the monsoon? Why or why not?

He would probably be disappointed in the simplistic nature of Curry et al.'s explanation, which cites only the heating of the lower atmosphere over the Asian continent as the cause of the monsoon. The higher latitude changes that Pédelaborde said caused the changes in the position of the ITCZ are not mentioned. Because Curry et al. have no data from the higher latitudes, their meterological explanation is a conservative one.

2. What is Ekman drift and how does it work?

When the wind blows across water, the water column reacts as if it were a pile of slabs of water. The 'top slab' of water is swept slightly to the right (in the northern hemisphere) of the direction of the wind because of the Coriolis force. This moving slab of water sets in motion the slab below it, which moves to the right of the motion of the one above it. This continues to happen with the cumulative effect of the water at a greater depths moving progressively more to the right of the water above it. This creates the 'Ekman spiral'. The net effect is move the water 90° to the right of the direction of the wind at the surface.

3. Why are nutrient concentrations higher in upwelling cells?

If the wind is moving from SW to NE (summer monsoon) along the coast of Oman, then water affected by the wind is swept to the southeast, away from the Omani shore. Water cannot move from the northwest because the Arabian peninsula is there. Therefore water comes up from depth to replace the water swept away by the wind.

This water from depth is laden with nutrients because organic matter is lysed at depth and there is not much biota at depth to uptake the nutrients as food. Upwelling brings this water to the surface.

In oceanic areas far from shore the same phenomenon is driven by positive wind stress curl. Upwelling occurs when water is locally pushed in opposite directions along the boundary of a fast moving jet of air and a slower moving air mass.

4. Why might the water temperature predicted from the O-18 of G. ruber shells be higher than that predicted based on equilibrium calcite precipitation and known values of O-18 in the regional water?

Globigerinoides ruber may calcify during transient cooler events (perhaps associated with short-term upwelling events). Because large numbers of shells may be produced during these brief cool events, your chances of measuring their isotopic composition are greater than your chances of measuring the relatively rarer shells produced during the intervening warmer periods.

5. Why is it expected that the nutrient rich water brought up from depth in the upwelling zone would be low in C-13?

Organic matter has very low d¹³C values because during photosynthesis ¹²CO₂ is incorporated into organic molecules at a higher rate than is ¹³CO₂ (fractionation). Most of the H¹³CO₃^- in upwelled water is derived from lysed organic matter.