Modeling the dynamical sinking of biogenic particles in oceanic flow

Monroy, Pedro; Hernández-García, Emilio; Rossi, Vincent; López, Cristóbal

doi:https://doi.org/10.5194/npg-24-293-2017

Articles | Volume 24, issue 2

https://doi.org/10.5194/npg-24-293-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

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Current perspectives in modelling, monitoring, and predicting...

https://doi.org/10.5194/npg-24-293-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 24, issue 2

Research article

|

29 Jun 2017

Research article |

| 29 Jun 2017

Modeling the dynamical sinking of biogenic particles in oceanic flow

Pedro Monroy, Emilio Hernández-García, Vincent Rossi, and Cristóbal López

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Final revised paper (published on 29 Jun 2017)
Preprint (discussion started on 15 Dec 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Referee report', Anonymous Referee #1, 13 Jan 2017
- AC1: 'Response to Referee #1', Pedro Monroy, 30 Mar 2017
RC2: 'Reviewer Comment', Anonymous Referee #2, 01 Feb 2017
- AC2: 'Response referee #2', Pedro Monroy, 30 Mar 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Pedro Monroy on behalf of the Authors (30 Mar 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (01 Apr 2017) by Vicente Perez-Munuzuri

RR by Anonymous Referee #1 (20 Apr 2017)

Suggestions for revision or reasons for rejection

I found the revised version of the manuscript much improved with respect to the original submission. I have only a remark and a typo detected to signal.

A part from these two points I think the manuscript is now ripe for publication.

1) On p.12 at the end of the page the authors write:
"To assess the impact of the Coriolis and of the inertial effects we compare the positions r^(co)(t), and r^(in)(t) with the simpler dynamics r^(in)(t) for each time t. " If I understood correctly the second r^(in) should be a r^(0)
Please check.

2) I have still a remark on the issue of chaoticity. More than a remark is that I would like to understand better the point made by the authors.

As far as I understood the authors provide evidence with new fig.4 that the root mean square difference between the horizontal particle position computed by using the simple settling model Eq.(9) and the refined one including the Coriolis term grows exponentially in time. Moreover the comment that the exponential rate of about 0.08days is in agreement with the order of magnitude of the Lyapunov exponent calculated using the same ROMS velocity model and region.

This seems to agree with my comment expressed in the previous report.

Now the issue is the following. Suppose you compute the root mean square deviation between the horizontal position of particles that all follow the same simple dynamics (9) but considering two sets of particles with the positions that are initially slightly different, by a small amount similar to what would be the displacement induced by the Coriolis term, say in 1day.
What would be the behavior of the root mean square displacement?
Since the system is chaotic the root mean square will be growing exponentially with the Lyapunov exponent (I think) close to 0.08 days^{-1}. Therefore the net result would be a displacement after 180 days similar to that observed in
fig.4.

In other terms my doubt can be restated with the following question. Is the effect of the Coriolis term
the same as the effect of a small displacement of the simpler settling dynamics (9)? If yes I think it is difficult to conclude about that “the inclusion of the Coriolis term would be required to properly model slowly sinking particles at high latitudes”.

I hope my point is clearer now. I would be very grateful if the authors could answer my question.

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RR by Anonymous Referee #2 (01 May 2017)

ED: Publish subject to minor revisions (further review by Editor) (01 May 2017) by Vicente Perez-Munuzuri

AR by Pedro Monroy on behalf of the Authors (11 May 2017) Author's response Manuscript

ED: Publish as is (11 May 2017) by Vicente Perez-Munuzuri

AR by Pedro Monroy on behalf of the Authors (19 May 2017) Manuscript

Short summary

We study the problem of sinking particles in a realistic oceanic flow, with major energetic structures in the mesoscale, focussing on marine biogenic particles. By using a simplified equation of motion for small particles in a mesoscale velocity field, we estimate the influence of physical processes such as the Coriolis force and the particle's inertia, and we conclude that they represent negligible corrections to passive transport by the flow, with added vertical velocity due to gravity.