Moving from chemistry to oceanography as a current chemistry PhD student? I am currently working my way towards a PhD in chemistry in a very good EU university. Things are running smooth and I expect to graduate within 1 to 2 years. But there is one big problem: the time spent in the lab made me realise that this is not the life I want. Although my passion for science is still intact after all those years, I have to admit that the lab work, the dreadful academic and private job market and the unexciting prospect of "parallel careers" have finally dented my motivation to pursue such a path.

I do, however, have a second passion in life: the ocean. I simply love earth, climate and ocean science about as much as I love chemistry, and seriously considered going for such studies instead. Since I started college, I have continuously taken classes in related subjects (biological oceanography, biogeochemistry, atmospheric physics...), and have enjoyed every bit of it. The only reasons why I picked chemistry for grad school were that I considered the outcome of the research I would do as more valuable for society (I specialise in cancer biochemistry) and the illusion that surely, I would get my own lab some day. But with the current physical sciences job market being grimmer than ever in both academia and private research, I have to accept the possibility of doing no research at all after graduating as the likeliest scenario. And the mere thought of ending up in careers such as consulting, no matter how lucrative, makes me want to off myself straight away.

On the other hand, the job prospects in marine and earth sciences appear somewhat more decent (please correct me if I am wrong here) - at least in the sense that you have better chances of working as a scientist in the end, although not necessarily in a tenure-track position or in an elite institution. This, coupled with my very strong interest in the field, has led me to consider quitting traditional chemistry for a field such as chemical oceanology and the likes. To do so, several branching pathways seem not entirely absurd:

1) Finishing my PhD in chemistry, and then jump into oceanography via post-doc training: this would be the easiest and safest option IF permanently moving from chemistry to oceanography is realistically doable. (It seems to me that the fine understanding of the physical and chemical processes common in living systems and natural milieus deriving from a PhD in basic chemistry could be a plus in that prospect).

If 1) was to be an impossible/unrealistic course of action, I guess my options would then be:

2) Finishing my PhD in chemistry, and then do a second PhD in oceanography: I am honestly not a huge fan of this idea, as it would considerably extend the duration of my studies. I have also read quite often that already holding a PhD will basically disqualify you from being admitted in any serious graduate programme (committees would understandably see you as a degree chaser, an eternally indecisive student or a pisstaker). I would however gladly follow that path, provided that it is actually possible to go for the second PhD route and if it was my only option.

3) Dropping out of my current PhD and start another one in oceanography as soon as possible: This would be the Mad Max card. I am obviously very, very reluctant to this idea, but would consider it if everything else was to fail.

In the end, my question(s) would be: which one of these scenarios appears the more realistic? Is 1) a plausible option, and do I have to consider the other, riskier courses of action?

I would welcome any insight from people experienced in the related fields or who have heard of similar situations.
Chemistry and oceanography are quite closely related, with a lot of people who explicitly overlap the two.  A nice example that I happen to be familiar with is Chris Reddy at Woods Hole, who works on marine chemistry, especially in the area of oil spills.  There are lots more like him, so I think that a transition via postdoc is entirely feasible to attempt.

Whether you stay in biochemistry or shift to oceanography, however, I think that you may wish to consider the broader scientific ecosystem of research opportunities.  Your view of the biochemistry world is probably somewhat distorted by an environment dominated by highly competitive "big PIs" with large labs.  There's a lot more to the research world than that, even in medical biochemistry.