Ossë vs Ulmo: Insubordination?

[Iluisa Olórin]

In The Book of Lost Tales: Part I - The Chaining of Melko, Ossë is said to have been "... wroth at the upheaval of his realm and feared the displeasure of Ulmo his overlord."

Later, in The Coming of the Elves, it is said that he felt an "... ever-smouldering jealousy and rebellion..." against Ulmo.

Can anyone reconcile this apparent contradiction for me? Why would Ossë rebel against Ulmo when he feared him?

Even though Ossë was, at this time, numbered among the Valar, was he not always subordinate to Ulmo? In The Coming of the Valar, he is said to have been subordinate "... for fear and reverence and not for love."

[redline2200]

I have not read that book myself, but I will try and answer your question.
Fisrt, Ossë was a Maia and Ulmo was a Vala, so Ossë is always under the power of Ulmo. Also, you can still be under someone and fear them, yet be in rebellion. Like when Adolf Hitler ruled Germany all the poeople under him had him as lord and they feared him, yet some were still in rebellion (just not neccesarily open rebellion). Now I know that is probably not a far comparison (Ulmo/Ossë and Hitler/Germans), but I think you understand what I mean.
There was no contradiction because Ossë could feel both of those feelings at the same time. Does it ever say that Ossë openly rebeled against Ulmo?

[Iluisa Olórin]

Having shown a genuine concern for his superior's reaction to the upheaval, it is difficult to conceive how Ossë, in the same breath, can be jealous of and rebellious against him.

My understanding is that, although a hierarchy exists, the Ainur are ultimately answerable to Ilúvatar and so are largely free to carve out their own courses. However, surely, being his subordinate, Ossë is also answerable for his actions to Ulmo?

I can see what you're driving at, but those who rebelled against Hitler were his enemies (including those in his own camp), the same which cannot be said of Ossë.

Certainly, Ossë has rebelled against Ulmo. On one occassion I can recall, in The Silmarillion, how Voronwë, the messenger sent by Turgon (whom Ulmo had led to Tumladen) from Gondolin, was saved by Ulmo from Ossë's storm (although, granted, it is an assumption that the storm was deliberate).

[gate7ole]

Ossë was a rare exception of a quick-tempered Ainu. At the first ages of the world, when nothing had yet awoken, Ossë was seduced by Morgoth and would have been at this side but for Uinen’s intervention. Besides he was not easily restrained by Ulmo. But let Tolkien talk instead of me:
From the Silmarillion:: Of the Maiar
Melkor hated the Sea, for he could not subdue it. It is said that in the making of Arda he endeavoured to draw Ossë to his allegiance, promising to him all the realm and power of Ulmo, if he would serve him. So it was that long ago there arose great tumults in the sea that wrought ruin to the lands. But Uinen, at the prayer of Aulë, restrained Ossë and brought him before Ulmo; and he was pardoned and returned to his allegiance, to which he has remained faithful. For the most part; for the delight in violence has never wholly departed from him, and at times he will rage in his wilfulness without any command from Ulmo his lord. Therefore those who dwell by the sea or go up in ships may love him, but they do not trust him.
As for the rebel you mention against Ulmo (Voronwë), it was not a rebel of Ossë, but mostly of Ulmo, who disagreeing with the Hiding of Valinor helped the Exiled Noldor.
My understanding is that, although a hierarchy exists, the Ainur are ultimately answerable to Ilϊvatar and so are largely free to carve out their own courses. However, surely, being his subordinate, Ossλ is also answerable for his actions to Ulmo?
Very true. They are independent and intelligent and disagreements among them are inevitable. And little diversions from the main course of action set by Manwë is forgivable. Remember, Ulmo forgave Ossë for his rebellion.