Floating in the waters of the equatorial pacific, an array of buoys collects and transmits data on long-term interactions between the ocean and the atmosphere, interactions that affect global climate.

A) atmosphere, interactions that affect

I made interactions plural, as having the correct form in this version makes more sense given that this is the OA.

This version correctly uses an appositive to continue discussion of the interactions.

B) atmosphere, with interactions affecting

In this version what the interactions are with is not clear and saying that the interactions are with something does not make sense.

C) atmosphere that affects

The use of the singular form affects seems to connect affects to atmosphere and thus distorts the meaning, conveying that the atmosphere, rather than the interactions, affects global climate.

D) atmosphere that is affecting

The use of that is affecting distorts the meaning, conveying that the atmosphere is affecting global climate.

E) atmosphere as affects

The construction as affects lacks anything indicating what affects the global climate.

The correct answer is A.

C to E isn't the correct answer because of its incomplete sense so we will eliminate them.
B isn't correct because the statement shows the effect but not the on going effect.
That's why A is the correct answer