Deep through-flow in the Bight Fracture Zone

Petit, Tillys; Thierry, Virginie; Mercier, Herlé

doi:https://doi.org/10.5194/os-18-1055-2022

Articles | Volume 18, issue 4

https://doi.org/10.5194/os-18-1055-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/os-18-1055-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 4

Research article

|

15 Jul 2022

Research article |

| 15 Jul 2022

Deep through-flow in the Bight Fracture Zone

Tillys Petit, Virginie Thierry, and Herlé Mercier

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Final revised paper (published on 15 Jul 2022)
Preprint (discussion started on 25 Apr 2022)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-248', Anonymous Referee #1, 04 May 2022

Short summary:

The article "Deep through-flow in the Bight Fracture Zone and its imprint in the Irminger Sea" presents the properties of the

throughflow through the Bight Fracture Zone (BFZ) from ship based and Arvor float observations and focusses mainly on the

property transformation of ISOW passing it . The transports and hydrographic

properties of the through-flow are presented and reveal a very variable throughflow of the BFZ.

Due to a small recirculöation in the middle of the BFZ vertical mixing is discussed.

By using two Arvor floats the influence of the through-flow on the ISOW in the Irminger Sea is attempted.

The paper concludes a significant influence of the throughflow through the BFZ on the ISOW properties

in the Irminger Sea.

General remarks:

I think the paper need some minor revisions as marked in the pdf and attached to this text.

the experimental setup was thoroughly though through an only leaves one open question for me.

The reasoning about the keyrole of the BFZ for counteracting freshening in the Irminger

Sea is not supported enough by the two floats available - I think this paret should be

written a little more vague or other observational data should be included in the discussion

(remarks in the text). For this reason I would propose to change the name of the work to something

less proposing a study of the absolute influence of the BFZ on the salinification of the

ISOW signal in the Irminger Sea since from the data base presented here this is not adequately possible.

Another point which is more a general point of discussion is the name of the water mass discussed -

ISOW or NEADW (see remark in the text).

Notes with the pdf:

page 1, L10

This is maybe a general point of discussion - whether to call the water mass ISOW or NEADW. In my understanding ISOW is really the overflow water at the ISR and FBC since it is modified almost directly when entering he Iceland basin - as you describe also in this article - hence, I always call it NEADW. The same would hold for DSOW -> but here we only know one name …

page 1, L13

allow

page 1, L18

homogenized

page 1, L19

Should be rather ISOW circulating in the Irminger Sea - or are you sure the ISOW is formed in the Irminger Sea?

page 1, L20

This

page 1, L20

results

page 2, L35

reach

page 2, L36

crosses

page 2, L49

from investigating

page 2, L51

by

page 2,L 56

2 Data and Methods -> general remark : I think it would be nice for completeness to give one sentence on the used toolboxes like TEOS-10 etc for the calculations

Additionally you state you use the methods from Petit et al. 2018 it would be nice to have one or two sentences summarizing the interpolation and treatment shortly.

page 3, L 67

Regarding the km scale here I would not call them basins - rather - channels ?

page 3, L69

200-m isobaths spacing from white at the surface to dark blue at greater depths

* erase, page 3

The deepest bathymetries are represented with darkest blue

page 3, L80

at,

page 4, L82

basins -> deep channels

page 4, L102

0.002 psu ? Or g/kg salinity units

page 6, L135

0.004 psu ?

page 6, L139

salinity

page 6, L148

areas

page 6, L148

East Reykjanes Ridge section

page 7, L152

eastern entrance

page 7, L56

East section (upper panels)

page 7, L156

Middle section (lower panels)

page 8, L164

the

page 8, L165

a

page 8, L

the

page 8, L166-168

Did you check the SPG index -> maybe it also related to different states of the SPG

page 9, L189

0.005 psu

page 9, L190

shows

page 9, L196

which

page 11, L 222

channels

page 11, L 230

channels

page 11, L 232

channels

page 11, L 234

from the Irminger Sea.

I am not sure about the exact origin - It might be the ISOW that passes CGFZ, mixes etc and is then transported along the western flank of RR ? ISOW from the Irminger Sea sounds like it is formed here.

page 11, L236-237

must originate from the Irminger Sea -> see comment above

page 12, L238

channels

page 12, L239

See comment above

page 12, L243

at a few week interval -> in an interval of several weeks

page 12, L250

channels

page 12, 256

from the Irminger Sea

page 12, L263

channels

page 13, L273

additional deep inflows -> could diapycnal mixing play a role here? Since you have a steep flanks in the middle part and a recirculation cell diapycnal mixing could be an additional possible source. - how about the import of LSW and SPMW into the section - does it change between im- and export in the BFZ?

page 13, L 278

isopycnal mixing -> diapycnl mixing? See my comment above

page 14, L 279

left hand side - > southern side?

* Highlight, page 14

basins

* Highlight, page 14

isopycnal mixing

* Highlight, page 14

isopycnal mixing

page 14, L301-302

See Holliday 2018 -> 1 Sv of the flow exiting the IC in the lNADW class is added to the uNADW class at OSNAP -> is 1 Sv really playing a key role when thinking about a through flow of unsteady ~1 Sv through the BFZ? Id rather say that the BFZ is supplying salt to the Irminger Sea but if this really plays a significant role compared to the saline inflow of water in the upper AMOC component in the Irminger current and the slight freshening of ISOW in the Irminger Sea through mixing with LSW is an open question to me. As the salinification of ISOW happens just south of the ISR (Devana 2021) and the ISOW has this very saline signature at the EGC at OSNAP EAST and at OSNAP WEST. I am wondering about the relative importance here.

page 14 L303-307

I would include the OSNAP observations here - the southward current band is not stable and possibly part of a recirculation cell within the Irminger Sea. Additionally concluding from one float I rather arbitrary.

page 14, L306

a local

page 14, L310

get

page 15,L 314

floats

page 15, L 315-317

I would include the mean circulation argument from eg. Fischer et al 2018 here - the central Irminger Sea is occupied by 2 large recirculation cells rather close to the Greenland shelf break.

page 15, L321 - 324

Maybe add Fox et al 2022

Citation: https://doi.org/10.5194/egusphere-2022-248-RC1
- AC1: 'Reply on RC1', Tillys Petit, 20 Jun 2022
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-248/egusphere-2022-248-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2022-248-AC1
RC2:
'Comment on egusphere-2022-248', Anonymous Referee #2, 20 May 2022

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-248/egusphere-2022-248-RC2-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2022-248-RC2
- AC2: 'Reply on RC2', Tillys Petit, 20 Jun 2022
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-248/egusphere-2022-248-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2022-248-AC2
RC3:
'Comment on egusphere-2022-248', Anonymous Referee #3, 10 Jun 2022

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-248/egusphere-2022-248-RC3-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2022-248-RC3
- AC3: 'Reply on RC3', Tillys Petit, 20 Jun 2022
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-248/egusphere-2022-248-AC3-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2022-248-AC3

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Tillys Petit on behalf of the Authors (21 Jun 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (25 Jun 2022) by Ilker Fer

AR by Tillys Petit on behalf of the Authors (28 Jun 2022)

Short summary

The Iceland–Scotland Overflow Water is a dense water carried within the lower limb of the Atlantic Meridional Overturning Circulation. From a combination of ship-based and Deep-Argo data gathered between 2015 and 2018, our study analyzes the pathways and evolution of its properties as it flows through a main fracture of the Reykjanes Ridge, the Bight Fracture Zone (BFZ). We show that 0.8 ± 0.2 Sv of ISOW flows through the BFZ and is mainly homogenized within the rift valley of the ridge.