Water mass structure in the South Water mass structure in the South  Atlantic and its decadal variabilityAtlantic and its decadal variability

Demidov A.N., Krayushkin E.V., Demidov A.N., Krayushkin E.V., Kalashnikova N.A., Chereshnuk S.A.Kalashnikova N.A., Chereshnuk S.A.

Moscow State Universitytuda@mail.ru

••

Main goalMain goal: : determine South Atlantic water mass determine South Atlantic water mass  structure and its longstructure and its long‐‐term variability.term variability.

•• TheThe

key objectskey objects

of the investigation are the Antarctic of the investigation are the Antarctic 

Intermediate and Bottom Waters (AAIW and AABW) and Intermediate and Bottom Waters (AAIW and AABW) and  the components of the North Atlantic Deep Waters the components of the North Atlantic Deep Waters 

(NADW)(NADW)

TasksTasks••

Determination of water mass structure and boundariesDetermination of water mass structure and boundaries

•• Analysis average characteristics in the transatlantic Analysis average characteristics in the transatlantic 

sectionssections

Water mass structure of the Atlantic oceanWater mass structure of the Atlantic oceanAAIW – Antarctic Intermediate WatersNADW – North Atlantic Deep Waters

UNADW – Upper NADWMNADW – Middle NADWLNADW– Lower NADW

MIW – Mediterranean Waters ISOW – Iceland-Shetland Overflow WatersLSW – Labrador Sea WatersDSOW – Denmark Strait Overflow Waters

UCPW – Upper Circumpolar WatersAABW – Antarctic Bottom WatersLCPW – Lower Circumpolar Waters

WSDW- Weddell Sea Deep Waters

*Black lines are the boundaries of waters according to location of maximal vertical salinity gradient

UCPW

How NADW components relate to water mass of the North How NADW components relate to water mass of the North Atlantic?Atlantic?What do bottom waters to the north from the Argentine What do bottom waters to the north from the Argentine basin consist of? What proportion of WSDW and LCPW is basin consist of? What proportion of WSDW and LCPW is presentpresent

in them?in them?

Wust, 1936; CFC fromMolinari et al., 1990

Rhein et al., 1995; Vanicek, Siedler, 2002

max min max min

UNADW S,CFC SUNADW T,S,

CFC Si,P

MNADW O2 CFCLSW O2

LNADW-old O2 , CFC

LNADW O2 ,CFC OLNADW O2 ,

CFC

Wust, 1936

Tsuchiya et al., 1992

Rhein et al., 1995

Schmitz, 1996

Andrie et al. 1998

UNADWMIW MIW+

LSWUpper LSW LSW+

MIWLSW

MNADWLSW ISOW+

EBW+DSOW

LSW+ISOW

DSOW, ISOW, AABW

CPW+LSW+ISOW

LNADW DSOW AABW+DSOW

DSOW DSOW, ISOW, AABW

DSOW

North Atlantic Deep North Atlantic Deep Water components. Water components. Classification and Classification and originorigin

Location of the Location of the maximal vertical maximal vertical gradients of the gradients of the different different characteristics and characteristics and water mass structure water mass structure at the A17 sectionat the A17 section

Max grad.TSO2SiPCFC

AAIW

UCPWUNADW

MNADW

LNADW

AABW AABW

NS

Max grad.TS

∆S

∆θ

Difference of water mass Difference of water mass structure, temperature and structure, temperature and salinity between 2003 and 1994 salinity between 2003 and 1994 A17 sections. A17 sections. Solid line marked 1994 data, Solid line marked 1994 data, dashed 2003. dashed 2003. Blue line Blue line ––

location location of maximal vertical temperature of maximal vertical temperature gradient, black gradient, black --

salinitysalinity

Run 1:

500-2000 m MIW, LSW, AAIW, WNACW –

2

Run 2: below 1500 mLSW,ISOW,DSOW,MIW,AABW

Run 3:

below 2500m LCPW, WSDW, NADW, SPDW

Bottle data of WOCE Sections –

initial data for OMP analysis

Extended Optimum Multiparameter AnalysisExtended Optimum Multiparameter Analysis

OMP package for Matlab by Karstensen, Tomczak, 1999

Source water typesSource water types

TT SS OO22 SiSi NONO33 POPO44

AAIW 4.00 34.21 5.84 18.89 28.40 1.91

MIW 11.11 36.30 4.34 8.66 16.20 1.12

LSW 3.08 34.86 6.88 9.08 16.53 1.06

ISOW 2.92 35.00 6.33 10.20 16.00 1.04

DSOW 0.25 34.93 7.05 7.91 12.09 0.91

NADW 3.02 34.95 6.35 14.11 17.68 1.16

AABW (WSDW) -0.74 34.65 5.90 114.8 31.38 2.07

uWNACW 18.90 36.60 4.72 2.00 6.00 0.25

lWNACW 9.40 35.10 4.06 15.00 24.00 1.70

SPDW 2.02 34.67 3.90 100.5 34.70 2.39

UCPW 2.50 34.60 4.60 70.00 29.00 2.20

LCPW 0.92 34.72 4.65 113.6 31.07 2.29

Source water types from WOA09

OMP Result OMP Result Run 1Run 1: A20: A20MIW, LSW, AAIW, WNACWBlack line –

water mass boundaries

%LSW

%AAIW

WNACW AAIW

UNADWLSW

WNACW AAIW

UNADWLSW

OMP Result OMP Result Run 1Run 1: A20: A20MIW, LSW, AAIW, WNACW

%MIW

%WNACW

WNACW AAIW

UNADWLSW

WNACW AAIW

UNADWLSW

OMP Result OMP Result Run 2Run 2: A06: A06LSW,ISOW,DSOW,MIW,AABW

%LSW

%ISOW

WB EB

UNADW

MNADW

LNADW AABW

UNADW

MNADW

LNADW AABW

WB EB

OMP Result OMP Result Run 2Run 2: A06: A06LSW,ISOW,DSOW,MIW,AABW

%DSOW

%AABW

WB EB

UNADW

MNADWLNADW

AABW

UNADW

MNADW

LNADW AABW

Eq. Ch. Brazil Basin Vema Ch. Arg. B.

Eq. Ch. Brazil Basin Vema Ch. Arg. B.

OMP Result OMP Result Run 3Run 3: A17: A17LCPW, WSDW, NADW, SPDW without Si

% WSDW% WSDW

% LCPW% LCPW

LNADW

LNADWMNADW

MNADW

80 60 40 20 0 20 40 606000

5000

4000

3000

2000

1000

0

80-40 %10-40 %

30-50 %70-45 %

0 - 5 %

50-60 %20 %10 %

20-10 %

10 %50-60 %10-20 %20-10 %

10-20 %

10-5 %20-40 %

70-55 %

10-20 %

10-30 %80-50 %

10-20 %

10-30 %

10-20 %70-30 %

60-40 %40-60 %

10-5 %20-40 %

60-40 %40-60 %

10-50 %

80-65 %

80-30 %10-20 %

10-20 %60-20 %

10 %20-40 %

40-60%60-40%

60-40%40-60%

10-40%

0-10%

10-20%

80-30%

MIW AAIW

+ UCPW

SPDW

LCPW

UNADW

MNADW

LNADW

NA

DW

LSW

ISOW

DSOW WNACW

AABW WSD

W

70-

55 %

40-55 %0-5 %

60-40 %

40-55 %0-5 %

60-40 %

0-20 %60 %

40-20 %

(EBW)

Dep

th

N S

All OMP Runs results schemeAll OMP Runs results scheme

Latitude

This work max min The main originUNADW S,CFC P, Si LSW, AAIW, MIWMNADW O2, P CFC ISOW, LSW, EBWLNADW O2 ,CFC P ISOW, AABW, DSOW

Origin of the NADW componentsOrigin of the NADW components

NADW components pathwaysNADW components pathways

[Morozov,Demidov et al.,2010]

Vema channelVema channel

Equatorial channelEquatorial channel

Potential temperature Potential temperature temporal variability temporal variability near bottom in the near bottom in the Vema and Equatorial Vema and Equatorial channels (minimal at channels (minimal at the each section).the each section).

map

ºC

ºC

LongLong--term variabilityterm variability

AABWAABW

AABW temporal and AABW temporal and spatial variability in spatial variability in the Vema Channelthe Vema Channel

Bot.θ,S

From Morozov, Demidov et al., Springer, 2010

θ

Stations along Vema Channel

Example of difference between Example of difference between 2009 and 1983 sections at the 242009 and 1983 sections at the 24ººSS

Computing average values. We used γn

approximation of the maximal vertical gradients position

∆S

∆θ

AAIW NADW

AABW

Temporal Temporal θθ,S variability of water mass ,S variability of water mass in DWBCin DWBC88--1111

S S ––

dashed, 24 S dashed, 24 S ––

solid, black horizontal line solid, black horizontal line ––

climate (Gouretsky, Koltermann)climate (Gouretsky, Koltermann)

θ

S

AAIW NADW

AABW

Integral temporal Integral temporal θθ,S variability of water mass at the sections,S variability of water mass at the sections88--1111

S S ––

dashed, 24 S dashed, 24 S ––

solid, black horizontal line solid, black horizontal line ––

climate (Gouretsky, Koltermann)climate (Gouretsky, Koltermann)

θ

S

11 S

11 S

11S

Conclusion••

Due to results of OMP analysis it is established that Due to results of OMP analysis it is established that NADW the South Atlantic consist mainly of ISOW and NADW the South Atlantic consist mainly of ISOW and LSWLSW

••

The Antarctic waters in the bottom layer in the Brazil The Antarctic waters in the bottom layer in the Brazil basin have LCPW share, approximately exceeding basin have LCPW share, approximately exceeding WSDW 2 timesWSDW 2 times

••

MNADW probably propagated from the eastern basin. MNADW probably propagated from the eastern basin. MNADW penetrates into the western basin through MNADW penetrates into the western basin through MAR only to the south of 20 NMAR only to the south of 20 N

••

In the Southern Atlantic we observed the cooling and In the Southern Atlantic we observed the cooling and desalination tendency of water mass below the surface desalination tendency of water mass below the surface layer (especially AAIW and AABW), that is in a good layer (especially AAIW and AABW), that is in a good agreement with results of [Levitus et al., 2005]agreement with results of [Levitus et al., 2005]

Thank you for your attentionThank you for your attention