On the modifications of the Denmark Strait overflow plume during its descent into the North Atlantic
Download
1 / 15

Kerstin Jochumsen 1 , Detlef Quadfasel 1 , Manuela Köllner 1,2 , and Stephen Dye 3 - PowerPoint PPT Presentation


  • 107 Views
  • Uploaded on

On the modifications of the Denmark Strait overflow plume during its descent into the North Atlantic. Kerstin Jochumsen 1 , Detlef Quadfasel 1 , Manuela Köllner 1,2 , and Stephen Dye 3 1 University of Hamburg, ZMAW, Germany 2 now at GEOMAR, Kiel, Germany 3 CEFAS, Lowestoft, UK.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Kerstin Jochumsen 1 , Detlef Quadfasel 1 , Manuela Köllner 1,2 , and Stephen Dye 3' - carson


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
On the modifications of the Denmark Strait overflow plume during its descent into the North Atlantic

Kerstin Jochumsen1, Detlef Quadfasel1, Manuela Köllner1,2, and Stephen Dye3

1 University of Hamburg, ZMAW, Germany

2 now at GEOMAR, Kiel, Germany

3 CEFAS, Lowestoft, UK


Motivation during its descent into the North Atlantic

Denmark Strait Overflow Water (DSOW) forms the densest part of North Atlantic Deep Water (~6 Sv after entrainment)

Dickson et al., 2002

Fischer et al., 2010

van Akenand de Jong, 2012


Open during its descent into the North Atlanticquestions

Will Arctic temperature/salinity variability be seen in downstream DSOW measurements?

Which water masses are responsible for the variability observed in the Deep Western Boundary Current?

EG Spill Jet

  • Is the influence of the East Greenland Spill Jet detectable in the downstream mooring time series?

from Vage et al. (2011), modified


Observations during its descent into the North Atlantic

Mooring arrays

DenmarkStraitsill (NORTH) – DSOW entrainmentregion (CENTRAL) – DSOW atAmmassalik (SOUTH)


Mooring during its descent into the North Atlanticdesigns

Denmark Strait sill array (NORTH)NORTH

σθ=27.8

σθ=27.85

σθ=27.8

Ammassalik array (SOUTH)


Array during its descent into the North Atlanticcoherence

Pot. temperature fluctuations are similar within the mooring arrays

NORTH

mean: -0.08°C ± 0.13°C

r=0.8

CENTRAL

pot. temperature [°C]

r>0.9

mean: 1.10°C ± 0.21°C

r>0.7

mean: 1.45°C ± 0.16°C

SOUTH


Array during its descent into the North Atlanticcoherence

Salinity fluctuations are small at DS sill and increase downstream

NORTH

mean: 34.900 ± 0.004

r=0.6

CENTRAL

r>0.8

salinity

mean: 34.897 ± 0.008

mean: 34.895 ± 0.010

r>0.9

SOUTH


Array during its descent into the North Atlanticcoherence

Velocity fluctuations are dependent on the plume position

NORTH

r=0.4

r=-0.4

SOUTH


Signal during its descent into the North Atlanticpropagation

pot. temperature

salinity

velocity

NORTH

NORTH

NORTH

r=0.8, 2d lag

r<0.3

CENTRAL

CENTRAL

r<0.4

16d lag

r<0.3

16d lag

r>0.7

10-14d lag

r>0.6

8-12 d lag

r>0.5

13-16d lag

SOUTH

SOUTH

SOUTH

Pot. temperature signals are advected (mean speed: 45 cm/s), salinity and velocity signals are strongly modified by entrainment


Mixing of Water Masses during its descent into the North Atlantic

DeepAmmassalik (SOUTH) measurementscloseto DS 5-7(CENTRAL)

→ entrainmentoccursmainlybetweenDS silland DS 5-7 (180 km downstream)


Mixing of Water Masses during its descent into the North Atlantic

Modified Atlantic Water

(from CTD sections)

East Greenland

CurrentWater

(e.g. Rudels et al., 2002)

DSOW at

Ammassalik

DSOW atthesill


Conclusions during its descent into the North Atlantic

  • good correlation of temperature time series → temp. signals are advected from the sill

  • low/no significant correlation in salinity and velocity

  • → entrainment processes strongly modify salinity/velocity

  • East Greenland current water is needed to obtain low salinities

  • entrainment is dominant between DS sill and DS 5-7 EGC spill jet plays a minor role for DSOW south of 64°N intermittent spill events likely combine to long term effects

  • downstream DSOW properties do not necessarily reflect Nordic Seas conditions (especially in salinity)


Conclusions during its descent into the North Atlantic

Will Arctic temperature/salinity variability be seen in downstream DSOW measurements?

Probably not, only if the signals are very pronounced.

Which water masses are responsible for the variability observed in the Deep Western Boundary Current?

The original overflow crossing the GSR, but also the Atlantic Water in the Irminger Sea, as well as the EGC spill jet waters.

  • Is the influence of the East Greenland Spill Jet detectable in the downstream mooring time series?

Yes, in low salinity signals.


Longterm during its descent into the North Atlanticperspective

DSOW transports, updated from Jochumsen et al. (2012) and Dickson et al. (2007)

no trends in transports, warming from 1998 - 2006, since then t is rather stable


The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299

NACLIM http://www.naclim.eu


ad