Status on Equatorial Indian Ocean – OceanSITES

Long-term measurements of currents in the equatorial Indian Ocean using deep-sea moorings –

Project funded by INCOIS/ MoES

byDr. VSN Murty

National Institute of Oceanography Regional Centre

176 Lawsons Bay Colony, Visakhapatnam

OceanSITES meeting in SIO30 Nov – 2 Dec. 2011

70 75 80 85 90 95 1005

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2570 75 80 85 90 95 100

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TS2 (17.5°N,89°E)

India

Lati

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Longitude° E

Equatorial Indian Ocean Observational Array since 2000

The current meter moorings project is being executed since February 2000. Servicing of the moorings is being done regularly onboard ORV Sagar Kanya.

EQCM1EQCM2EQCM3

Mooring Location

Duration of the moorings at each location D: Deployment R: Recovery 2000 2000-02 2002-03 2003-04 2004-06 2008-09 2009-10

EQCM 1[Equator, 93°E]

D 13 Feb ‘00

To

R 21 Dec ‘02

D 23 Dec ‘00

to

R 30 Mar ‘02

D 01 Apr 2002

To

R 23 Sep 2003

D 25 Sep 2003

to

R 05 Nov 2004

D 07 Nov2004

To

R 13 Sep 2006

D 15 Sep 2006

To

R 04 Jan 2009

D 05 Jan 2009 To

R 03 Oct 2009

EQCM 2[Equator, 83°E]

D 14 Dec ‘00

To

R 24 Mar ‘02

D 26 Dec 2002

To

R 17 Sep 2003

D 19 Sep 2003

To

R 24 Oct 2004

D 26 Oct 2004

To

R 19 Sep 2006

D 21 Sep 2006

To

R 30 May 2008

D 01 Jun 2008

To

R 08 Oct 2009

EQCM 3[Equator, 77°E]

D 10 Sep 2003

To

R 17 Oct 2004

D 18 Oct 2004

To

R 25 Sep 2006

D 27 Sep 2006

To

R 25 May 2008

D 27 May 2008

To

R 22 Oct 2009

Update status of 4 deep-sea current meter moorings in equatorial Indian Ocean

Each mooring has one uplooking 75 kHz ADCPs at 400 m and RCMs at 3 levels of nominal depths of 1000 m, 2000 m and 4000 m.OOS program would continue till 2012. Planning to extend the program for another 5 years [2012-2017]

Mooring Location

Duration of the moorings at each location D: Deployment R: Recovery 2009-10 2010 – 2011 2011 - 2012

EQCM1 – [1N, 93E]

EQCM 1 – [Eq., 93E]

EQCM1 – 1S, 93E]

D 01 Oct 2009 R 11 Oct 2010

D 05 Oct 2010 R 9Oct 2010

D 02 Oct 2009 R 6 Oct 2010

D 11 Oct 2010 R 2011

D 10 Oct 2010 R 2011

D 08 Oct 2010 R 2011

NOT DONE due to non-availability of the

vessels

EQCM 2[Equator, 83°E]

D 10 Oct 2009 R 01 Oct 2010 D 03 Oct 2010 R 2011 NOT DONE due to

non-availability of the vessels

EQCM3 – [1N, 77E]

EQCM 3 – [Eq., 77E]

EQCM3 – 1S, 77E]

D 21 Oct 2009 R 23 Sep 2010

D 24 Oct 2009 R 25 Sep 2010

D 20 Oct 2009 R 28 Sep 2010

D 24 Sep 2010 R 2011

D 27 Sep2010 R 2011

D 29 Sep 2010 R 2011

NOT DONE due to non-availability of the

vessels

Update status of 7 deep-sea current meter moorings in equatorial Indian Ocean

Each mooring has one uplooking 75 kHz ADCPs at 400 m and RCMs at 3 levels of nominal depths of 1000 m, 2000 m and 4000 m.

OOS – Deep Sea Current meter moorings that are to beIncluded in the OceanSITES list from the Indian Ocean

1)1N, 93E2)Eq., 93E3)1S, 93E4)Eq., 83E5)1N, 77E6)Eq., 77E7)1S, 77E

• To generate long-term currents data from the equatorial Indian Ocean from 7 deep-sea mooring locations spread across and along the equator from 77E to 93E.

• To describe the intraseasonal, interannual and long-term variability of currents in the equatorial Indian Ocean.

• To decipher the ocean processes and dynamics those impact the surface and subsurface variability by employing various model simulations to understand climate variability of the region.

• To study the deep-sea circulation from observations and model simulations in the equatorial Indian Ocean.

Objectives

Generated a decade long time series current data at 93E location, 9 years long time series data at 83E and 7 years long time series at 77E in the eastern equatorial Indian. Additionally 4 moorings were deployed in 2009 - at 1°N, 77°E; 1°S, 77°E, and 1°N, 93°E; 1°S, 93°E.

Up-to-date data till 2010 were submitted to INCOIS and NIO, Goa.

Identified and documented the intraseasonal variability in meridional currents at biweekly (14 day) period in the upper 1000 m from both observations and OGCM model simulations [Sengupta, Retish, VSN Murty and V Fernando, JGR, 2004].

Identified and documented the intraseasonal variability in meridional currents at 10-20 day period in the deep-ocean waters (2000 m and 4000m) and its linkage to the surface wind forcing, from observations and OFES model simulations [Ogato, Masumoto, VSN Murty and MSS Sarma, JGR, 2008].

Achievements

Achievements

Identified and documented the intraseasonal variability in observed equatorial currents in relation to the Indian Ocean Dipole mode events [David, D.T., S. Prasanna Kumar, P. Byju, M.SS. Sarma, A. Suryanarayana and VSN Murty (JGR (Oceans), 2011].

360 nm

Plan of Cruises from 2012 onwards during XII plan –

i) Two separate cruises to complete servicing of 7 mooringsii) To orient optimum technical staff in the deep-sea mooring operations

Thank You

David, D.T., S. Prasanna Kumar, P. Byju, M.S.S. Sarma, A. Suryanarayana and V.S.N. Murty (2011) Observational evidence of lower frequency Yanai wave in the central equatorial Indian Ocean. J. Geophys. Res., 116(6); 2011; doi:10.1029/2010JC006603, 17 pp.

Ogata, T.; Sasaki, H.; Murty, V.S.N.; Sarma, M.S.S.; Masumoto, Y. (2008) Intraseasonal meridional current variability in the eastern equatorial Indian Ocean. J. Geophys. Res. (C: Oceans): 113(7); doi:10.1029/2007JC004331, 15 pp.  Cadden; D.D.H.; Subrahmanyam; B.; Chambers; D.P.; Murty; V.S.N. (2008) Surface and subsurface geostrophic current variability in the Indian Ocean from altimetry. Mar. Geod.: 32; 19-29.

Sengupta, D., Senan, Retish. Murty, V.S.N., Fernando, Vijayan. (2004). A biweekly mode in the equatorial Indian Ocean. J. Geophys. Res., 109, C10003, doi: 10.1029, 2004JC002329.

Publications

Conclusions

• The presentation highlights the recent studies in the EIO using the OOS currents data.

• Current variability across-the equator at 93E location is presented for the period from Sept 2006 - October 2010.

• Spring EUC occurred consistently in March-April at 93E. Monsoon season intraseasonal jets are noticed in July-August.

• Observational evidence to the meandering of the EUC and Jet. Meandering is more visible in Spring season.

Conclusions

• The presentation highlights the recent studies in the EIO using the OOS currents data.

• Current variability across-the equator at 93E location is presented for the period from Sept 2006 - October 2010.

• Spring EUC occurred consistently in March-April at 93E. Monsoon season intraseasonal jets are noticed in July-August.

• Observational evidence to the meandering of the EUC and Jet. Meandering is more visible in Spring season.

Conclusions

• The presentation highlights the recent studies in the EIO using the OOS currents data.

• Current variability across-the equator at 93E location is presented for the period from Sept 2006 - October 2010.

• Spring EUC occurred consistently in March-April at 93E. Monsoon season intraseasonal jets are noticed in July-August.

• Observational evidence to the meandering of the EUC and Jet. Meandering is more visible in Spring season.

Last servicing of 7 mooring was done during October – November 2010

Servicing of theseMoorings could not be done in 2011due to non-availability of the vessels.

Current variability at 93E locationduring 2006 - 2010

Zonal current structure (96-464 m) at 0,93E during Sep 2006 – Dec 2008

2006 16-S 6-D 25-F 17-M 6-A 26-O 15-J 5-Ap 25-J 14-Sep 4-D 2008

Dominant eastward flows in the entire sub-surface layer

Zonal current structure (104-472 m) at Eq., 93E during Jan. 2009- Oct. 2009

2009 6-J 2-F 1-M 28-M 24-A 21-M 17-J 14-Jy 10-Au 6-Sep 3-O 2009

Winter & Spring EUC in 2009. Monsoon season EUC in 2009

Time

Dep

th(m

)

Zonal current(m/s) structure at 93E00 for 48 - 368 m layer

06-Oct-200911-Nov-200918-Dec-200924-Jan-201002-Mar-201008-Apr-201015-May-201021-Jun-2010 28-Jul-201002-Sep-201009-Oct-2010

50

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Zonal current structure (48-368 m) at Eq., 93E during Oct 2009- Oct 2010

2009 6-O 11-N 18-D 24-Jan 2-M 8-Apr 15-M 21-Ju 28-Jy 2-Sep 9-O 2010

Fall Jet in Nov 2009, Spring EUC & Jet ’10. Intraseasonal monsoon jets.

Time

Dep

th(m

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Zonal current(m/s) structure at location 93E1N for 144 - 480 m layer

02-Oct-200908-Nov-200915-Dec-200922-Jan-201028-Feb-201007-Apr-201014-May-201021-Jun-2010 28-Jul-2010 04-Sep-201011-Oct-2010

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Zonal current structure (144-480 m) at 93E, 1N during 2009-2010

2-O 8-N 15-D 22-Jan 28-F 7-Apr 14-M 21-Ju 28-Jy 4-Sep 11-O 2010

EUC in March 2010 & Semi-annual variation is evident.

Time

Dep

th(m

)

Zonal current(m/s) structure at 93E00 for 48 - 368 m layer

06-Oct-200911-Nov-200918-Dec-200924-Jan-201002-Mar-201008-Apr-201015-May-201021-Jun-2010 28-Jul-201002-Sep-201009-Oct-2010

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350 -0.8

-0.6

-0.4

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Zonal current structure (48-368 m) at Eq., 93E during 2009-10

6-O 11-N 18-D 24-Jan 2-M 8-Apr 15-M 21-Ju 28-Jy 2-Sep 9-O 2010

Fall Jet in Nov 2009, Spring EUC & Jet ’10. Intraseasonal monsoon jets.

Time

Dep

th(m

)Zonal current(m/s) structure at location 93E1S for 48 - 384 m layer

03-Oct-200908-Nov-200915-Dec-200921-Jan-201027-Feb-201005-Apr-201012-May-201018-Jun-2010 25-Jul-201030-Aug-201006-Oct-2010

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3-O 8-N 15-D 21-Jan 27-F 5-Apr 12-M 18-Ju 25-Jy 30-Au 6-O 2010

Zonal current structure (48-384 m) at 93E, 1S during Oct 2009-10

Fall Jet ‘09 Spring EUC & Jet ‘10. Intraseasonal Monsoon Jets

Zonal currentstructures in upper 400 mat 1N, Eq., 1S at 93E showsimilar structures at Eq. and 1S, suggesting the extent of Jets and EUC across the Equator up to 1S.

1S, 93E

6 Oct. 2009 08 Apr 2010 6 Oct. 2010

1N, 93E

Eq, 93E

Meridional current structure across the Equator at 93E during 2009-10

Time

Depth(m

)

Meridional current(m/s) structure at location 93E1N for 144 - 480 m layer

02-Oct-200908-Nov-200915-Dec-200922-Jan-201028-Feb-201007-Apr-201014-May-201021-Jun-2010 28-Jul-2010 04-Sep-201011-Oct-2010

150

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400

450 -0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

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Time

Depth(m

)

Meridional current(m/s) structure at location 93E00 for 48 - 368 m layer

06-Oct-200911-Nov-200918-Dec-200924-Jan-201002-Mar-201008-Apr-201015-May-201021-Jun-2010 28-Jul-201002-Sep-201009-Oct-2010

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350 -1

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Time

Depth(m

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Meridional current(m/s) structure at location 93E1S for 48 - 384 m layer

03-Oct-200908-Nov-200915-Dec-200921-Jan-201027-Feb-201005-Apr-201012-May-201018-Jun-2010 25-Jul-201030-Aug-201006-Oct-2010

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3-O 8-N 15-D 21-Jan 27-F 5-Apr 12-M 18-Ju 25-Jy 30-Aug 6-O2010

1N, 93E

Eq, 93E

1S, 93E

Thank You

Period in days

EIO experiencedIOD event in 2002

Intraseasonal variability at 30-50 d penetrates up to 4000 m depth and the ISV period increases with depth: 75 d at 500-1000m and 85 d at 2 km.

Period in days

Intraseasonal variability at 30-40 d penetrates up to 4000 m depth and the ISV period increases with depth: 85 d at 500-1000m and 110 d at 2-4 km.

EIO experiencedIOD events in 2005andin 2006

Impact of equatorial zonal currents on thealongshore currents off east coast of India

1. Zonal current variability at Eq., 93E during May – Oct. 2010

2. Alongshore current variability off Visakhapatnam at the same period3. Comparison of the zonal currents and alongshore currents at 48 m depth4. Spectra in the alongshore currents at different depths.

Zonal current structure (48 – 96 m) at Eq., 93E from May-Oct. 2010

Alongshore current structure (48 – 96 m) at Visakhapatnam

With a lag of 21 days, the alongshore currents do relate to the Zonal current at the Equator and the linkage is through Kelvin Waves

Spectra of alongshore currents off Visakhapatnam at 24, 56 & 92 m

The spectral peaks at 21 d and 24 d at 24 m, 56 m depth reveal theEquatorial connection in the shelf currents at 100 m water depth

360 nm

Plan of Cruises from 2012 onwards during XII plan –

i) Two separate cruises to complete servicing of 7 mooringsii) To orient optimum technical staff in the deep-sea mooring operations

Conclusions

• The presentation highlights the recent studies in the EIO using the OOS currents data.

• Current variability across-the equator at 93E location is presented for the period from Sept 2006 - October 2010.

• Spring EUC occurred consistently in March-April at 93E. Monsoon season intraseasonal jets are noticed in July-August.

• Observational evidence to the meandering of the EUC and Jet. Meandering is more visible in Spring season.

• Meridional currents show the observational evidence of the opposing currents at 1N and 1S at biweekly intervals – more clear in winter months.

• During the IOD events the intraseasonal variability at 30-50 day period penetrates up to 4 km.

• The zonal currents at Eq, 93E during May-October 2010 are compared with the alongshore currents off Visakhapatnam during the same period.

• A lag of 21 days in the alongshore currents relates the alongshore currents with the equatorial zonal currents through the propagation of downwelling and upwelling Kelvin waves.

Conclusions contd…

Zonal currentstructures in the upper 400 mat 1N/1S, 77E &Eq. , 83Edo suggest large scaleextent of EquatorialUndercurrent (EUC) across Equator.

Fall jet – 3 dSpring jet – 15 d

1N, 77E

Eq, 83E

1S, 77E

6 Oct. 2009 08 Apr 2010 6 Oct. 2010

Period in days

Intraseasonal variability at 50-60 day period is dominant.

OFES simulations showing large scale meander of spring and fall jets in EIO

October 11, 2003 April 14, 2004

Comparison of OFESand ADCP currents

Semi-annual period of 180 day in U and bi-weekly wave of 15 day period in V are evident.

ADCP data analysis at 77E

At 38 m At 94 m