Dear Authors,

I have just read the new posted replies to the reviews.
Overall, I find that you are doing a good job in taking them into account,
and that the proposed changes respond well to the comments posted.
There is just one part that left me somehwat puzzled (here, I cite it
from the reply to reviewer 2):

... the uncertainty of the 210Po export flux was on average
2-fold larger than the value of 210Po export flux.
When the uncertainty propagated from all the variables
mentioned above confirms that our estimates are the right order of magnitude,
we feel justified in publishing the results, and confident...

2-fold for me means 'double'... If that's correct, I understand that the
uncertainty is twice the export flux. Thus it implies that one is not sure of even
the sign of the export flux.
This might be the case (except if I misunderstood the statement),
but reading the abstract, I got the feeling that
the results were more certain than that.

So, if I understood correctly and based on these changes in the manuscript,
I believe that it is necessary to modify slightly the abstract
and that refering to this careful estimate of the uncertainty might be warranted.

With best regards, Gilles Reverdin

Dear Authors,

thank-you to have modified the abstract and for the minor changes that you have made in the paper.

With best regards, Gilles Reverdin.