Figure 5 shows a leading principal component (aka Empirical Orthogonal Function;

Question

Figure 5 shows a leading principal component (aka Empirical Orthogonal Function; EOF) of sea surface height (SSH) in the North Pacific Ocean (as measured by earth orbiting satellite altimeters) that is associated with the NPGO.
Figure 5: The second principal component of NE Pacific SSH derived from satellite data. Areas colored red and blue are of opposite sign. (http://www.o3d.org/npgo)
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(a) In just a few words, describe how the sea surface height (SSH) covaries across the NE Pacific based on the principal component for SSH shown in Fig. 5. (b) Draw a schematic of the circulation associated with the subtropical gyre and subpolar gyre in the region of the NE Pacific shown in Fig. 5. (c) The SSH pattern in Fig. 5 can also be used as an indicator of variations in the ocean pressure below the surface. Suppose that the SSH stands anomalously high equatorward of 40°N and anomalously low poleward of 40°N (i.e., the anomaly in SSH would look like Fig. 5). This would correspond to the positive phase of the NPGO. Assuming that the surface ocean circulation is in geostrophic balance with the near surface pressure field associated with the changes in SSH, what influence would the positive phase of the NPGO have on the strength of the subtropical and subpolar gyre circulations? (d) What influence would the negative phase of the NPGO have on strength of the subtropical and subpolar gyre circulations?

Explanation / Answer

a)The sea surface covers a considerably smaller area when compared to normal sea levels and mostly the sea level is covered with land area which may be eroded due to the sea waters.This sea surface height is greatly influenced in the pacific region due to emerging waves in the region.

b)The circulation associated with subtropical gyre ad subpolar gyre in the region of pacific is different from each other. The circulation in subtropical gyre is somewhat hotter and the circular associated with subpolar gyre is colder and may be present in the form of ice structure.

c)The positive phase of NPGO would have more pressure exposed on the strength of subtropical and subpolar gyre and the waves may blow out with more strength than usual strength.

d)The negative phase of NPGO would hav opposite effect as that of the positive phase and due to this,the strength of the blowing waves may decrease than the normal strength of the waves and the pressure decreases to a lesser value.

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