Arlindo mixing : CTD and hydrographic data from the August 1993 and January 1994 cruises

446 Pages·1996·39 MB·English

by  Mele, Philip A., author

Arlindo Mixing
AM93 - AM94
CTD and Hydrographic Data
Technical Report: LDEO-96-6
Lamont-Doherty
Earth Observatory
of Columbia University

Arlindo Mixing:
CTD and Hydrographic Data
from the August 1993 and
January 1994 Cruises
Philip A. Mele
Bruce A. Huber
Arnold L. Gordon
A. Gani llahude
Pusat Penelitian Dan Pengembangan Oseanologi
of the Indonesian Institute of Sciences
Kevin Sullivan
Rosenstiel School of Marine and Atmospheric Science
University of Miami
John Marra
Technical Report: LDEO-96-6
Lamont-Doherty Earth Observatory
of Columbia University
Palisades, New York
Lamont-Doherty
Earth Observatory
of Columbia University

Introduction
Inter-ocean transport within the Indonesian seas is the primary means of exporting excess
freshwater from the North Pacific Ocean. The efficiency of this transfer dictates to a large
measure the meridional overturning of the Pacific and Indian Oceans and perhaps of the
global thermohaline "conveyor belt" circulation. The Indonesian throughflow is relevant to
ENSO as it allows "seepage" of the western Pacific's warm pool water into the Indian
Ocean, adjusting the volume of the warm pool. Furthermore, the regionally intense tidal
induced mixing may govern to some extent the SST and sea-air coupling, with feedback on
ENSO. These mixing processes enhance buoyancy fluxes, inducing locally strong
upwelling and influencing the circulation pattern.
The Arlindo Project' was conceived to investigate the oceanography of the Indonesian seas
in a joint oceanographic research endeavor of Indonesia and the United States.
The Arlindo Project - Background
The primary goal of Arlindo is to observe the circulation and water mass stratification to
sufficient detail to allow for a thorough description of the source, spreading patterns and
dominant mixing processes of the waters influencing the Indonesian seas. Such products
can be used for the development of ocean circulation models for the Indonesian seas; large
scale coupled ocean/atmosphere models sufficient for prediction of climate and global
change; understanding of the environmental conditions within the Indonesian seas and
improved understanding of the factors that affect primary productivity and associated
fisheries within Indonesian waters.
The specific objectives of Arlindo are incorporated in each of its three phases:
Phase /, Arlindo Mixing
The field work for Phase I of Arlindo was carried out in 1993 and 1994. Phase I consisted
of an extensive array of CTD, tracer and productivity stations within the interior seas of
Indonesia. A summary of the results was presented at the WestPac III meeting in Bali, 22-
26 November 1994. The main objective of Phase I was to use water properties to identify
the main advective pathways of the throughflow for both monsoon phases. A Phase I
biological component investigated rates of primary production and evaluated if enhanced
vertical mixing influences primary production.
Phase //, Arlindo Circulation
The objectives of Arlindo Circulation (1996-1997) are to resolve the throughflow transport
and velocity field across the central passages of the Indonesian seas; extend the Arlindo
1993/94 CTD/CFC coverage both temporally-to 1996/97, and regionally to the eastern
Banda Sea. The Arlindo Circulation mooring design, based on Arlindo Mixing results,
will measure the mean and variable current and thermohaline stratification associated with
the inter-ocean throughflow for a 13 or 14 month period. The moorings are placed within
the dominant passages crossing a 1.5°S to 3°S band from Kalimantan to Irian Jaya which
marks a relatively shallow ridge system dividing the northern and southern Indonesian
seas.
I
Arlindo is an acronym tor Arus Lintas Indonen. meaning 'throughflow' in Bahasa Indonesia
1
Digitized by the Internet Archive
in 2020 with funding from
Columbia University Libraries
https://archive.org/details/arlindomixingctdOOmele
Introduction
Inter-ocean transport within the Indonesian seas is the primary means of exporting excess
freshwater from the North Pacific Ocean. The efficiency of this transfer dictates to a large
measure the meridional overturning of the Pacific and Indian Oceans and perhaps of the
global thermohaline "conveyor belt" circulation. The Indonesian throughflow is relevant to
ENSO as it allows "seepage" of the western Pacific's warm pool water into the Indian
Ocean, adjusting the volume of the warm pool. Furthermore, the regionally intense tidal
induced mixing may govern to some extent the SST and sea-air coupling, with feedback on
ENSO. These mixing processes enhance buoyancy fluxes, inducing locally strong
upwelling and influencing the circulation pattern.
The Arlindo Project1 was conceived to investigate the oceanography of the Indonesian seas
in a joint oceanographic research endeavor of Indonesia and the United States.
The Arlindo Project - Background
The primary goal of Arlindo is to observe the circulation and water mass stratification to
sufficient detail to allow for a thorough description of the source, spreading patterns and
dominant mixing processes of the waters influencing the Indonesian seas. Such products
can be used for the development of ocean circulation models for the Indonesian seas; large
scale coupled ocean/atmosphere models sufficient for prediction of climate and global
change; understanding of the environmental conditions within the Indonesian seas and
improved understanding of the factors that affect primary productivity and associated
fisheries within Indonesian waters.
The specific objectives of Arlindo are incorporated in each of its three phases:
Phase 1, Arlindo Mixing
The field work for Phase I of Arlindo was carried out in 1993 and 1994. Phase I consisted
of an extensive array of CTD, tracer and productivity stations within the interior seas of
Indonesia. A summary of the results was presented at the WestPac III meeting in Bali, 22-
26 November 1994. The main objective of Phase I was to use water properties to identify
the main advective pathways of the throughflow for both monsoon phases. A Phase I
biological component investigated rates of primary production and evaluated if enhanced
vertical mixing influences primary production.
Phase II, Arlindo Circulation
The objectives of Arlindo Circulation (1996-1997) are to resolve the throughflow transport
and velocity field across the central passages of the Indonesian seas; extend the Arlindo
1993/94 CTD/CFC coverage both temporally, to 1996/97, and regionally to the eastern
Banda Sea. The Arlindo Circulation mooring design, based on Arlindo Mixing results,
will measure the mean and variable current and thermohaline stratification associated with
the inter-ocean throughflow for a 13 or 14 month period. The moorings are placed within
the dominant passages crossing a 1.5°S to 3°S band from Kalimantan to Irian Jaya which
marks a relatively shallow ridge system dividing the northern and southern Indonesian
seas.
I
Arlindo is an acronym for Arus Lintas Indonen. meaning throughflow' in Bahasa Indonesia
1
Phase III, Arlindo Monitoring
(1998 to 2007) is a long term monitoring program of the throughflow to enable study at
time scales of ENSO events. The results of Arlindo Circulation will guide the formulation
of an efficient monitoring plan. Long term monitoring will insure detection of changes in
throughflow associated with ENSO.
The Arlindo Implementation Agreement was signed by Prof. Arnold L. Gordon, Professor
of Oceanography at Columbia University and Prof. Dr. Kasijan Romimohtarto, Director of
Pusat Penelitian Dan Pengembangan Oseanologi of the Indonesian Institute of Sciences
(LIPI) in August 1992. This is a project under the Memorandum of Understanding for
Collaboration in Climate Research between Indonesia and the United States of America,
signed in Washington DC by NOAA for the US and LAPAN for Indonesia on 28 October
1992. The Project Design for Phase I was prepared in August 1992 and signed by the
heads of the two national components, Arnold L. Gordon of Columbia University, USA
and A. Gani Ilahude of Pusat Penelitian Dan Pengembangan Oseanologi, LIPI, Indonesia.
The data analysis phase will be carried out by US and Indonesian scientists following the
plan presented in the August 1992 Implementation Agreement.
The field phase of Arlindo began in 1993. This is the first US report of the Arlindo
Project, presenting oceanographic data collected during the Arlindo Mixing cruises of 1993
and 1994.
The Arlindo Mixing Cruises
Arlindo Mixing consisted of 2 cruises, in order to sample the integrated effects of the
southeast and northwest monsoons.
The Arlindo Mixing "August 1993" southeast monsoon cruise aboard the Baruna Jaya I left
Jakarta at 1430 on 6 August 1993 and returned to Jakarta on 12 September 1993. Port
stops were made at Bitung, Ambon and Kupang. The science team consisted of 7 US
scientists and 13 Indonesian scientists, including the chief scientist A. Gani Ilahude.
During the 38 day cruise (counting departure and return days), 103 CTD stations and five
12 hour productivity stations were obtained (Table I and Figure I).
Baruna Jaya I left Jakarta for the Arlindo Mixing “January 1994” northwest monsoon
cruise at 1215 local time on 26 January 1994 and returned to Jakarta at 0800 local on 28
February 1994. Port stops were made at Kupang and Bitung. The science team consisted
of 9 US scientists and 14 Indonesian scientists, including the chief scientist A. Gani
Ilahude. During the 34 day cruise (counting departure and return days), 106 CTD stations,
46 XBT T-7 probes and five 12 hour productivity stations were obtained (Table I and
Figure 2). The total number of CTD stations for both Arlindo Mixing cruises is 209,
providing excellent spatial coverage of the main deep water channels for each monsoon
season.
Data Collection and Processing Methods
August 93 Cruise (AM93)
CTD/Oxygen
A total of 103 CTD 12 bottle rosette stations were obtained at 85 ship’s stations during the
AM93 cruise (Table 1 and Figure 1). At the CTD stations, water samples were drawn for
9
120° 125° 130°
Figure 1. AM93
110 115° 120° 125° 130° 135
Figure 2. AM94
3
salinity and oxygen (which are also used for <ca3ibrailiiG© «f ttfofc C’TD sensors), for the
chemical tracers of CFC and Tr/He and for productive Tneasaw^mTcts.
The CTD package consisted of the LDEO NBJS MKJJJ CTD S/N 2W9 mounted inside an
aluminum frame with 12 10-liter water sample bottles manufactured by ODF/Scripps.
Salinity samples were run on a Guildline 8400A salinometer standardized against OSI
Standard water batch PI23 (K15 = 0.99994). Standards were run at the start and end of
each session, and drift corrections were applied to the calculated .salinity values based on
standardization drift. Replicate and substandard samples were collected on 3 casts 26, 53.
and 77. The salinometer was installed in a .small darkroom, in which environmental
temperature control was poor. The temperature typically varied by !-3°C during the course
of one run of 24-36 samples. The salinometer was run on ship's power (220V/50Hz).
Oxygen samples were titrated using a modified Winkler procedure with amperometric
endpoint detection. The apparatus used was desmned and constructed by C. Lansdon of
LDEO.
Tracers
The analyses for two cholorfluorocarbons (CFCs), CFC-11 and CFC-12, were made using
shipboard methods described by Bullister and Weiss (1988). Water samples were drawn
and stored temporarily in lOOcc glass syringes. The dissolved CFCs were purged from
approximately 50 ml aliquots and trapped prior to separation via gas chromatography. The
response of an electron-capture detector was quantitated as integrated areas that were
proportional to the picomoles of CFCs.
The concentrations of the CFCs in water and air were calculated using external gas
standards. The aqueous and gaseous analyses were first corrected for any blank due to the
analytical system using a weighted average of the four surrounding appropriate blank
analyses. The temporal variation of the detector was compensated for by calculating a
normalization factor for each analysis. The normalization factor is determined by a
polynomial regression on groupings of analyses of a reference standard gas volume (2.97
ml) versus time. Equations that closely resemble straight lines were fit to groupings of
normalized standard analyses to yield calibration curves. These calibration curves were
applied to the aqueous and gaseous sample analyses to result in the concentrations of the
CFCs. A final correction was applied to aqueous analyses. This correction was estimated
from the samples collected in waters that were very likely free of CFCs and was to
compensate for any trace CFCs originating from the sampling bottles and/or handling.
Biology
At each CTD station along the cruise tracks, samples for chlorophyll analysis were
collected, either from a Niskin tripped just below the surface, or using a bucket. 200-500
ml of water was filtered through a Millipore FIA filter. The material on the filter was
extracted in 90% acetone for 24 hours, and the extract's fluorescence was measured on a
Turner Designs Model 10 fluorometer. The fluorometer was calibrated using pure
chlorophyll a. These data are reported in this document. At five stations on each cruise,
samples were also collected for incubations with C-14 and for dissolved oxygen analysis.
These latter data are reported elsewhere".
1
Kinkade, C.S . J Marra. C. Langdon and C Knudson 1996. Phytoplankton
stocks and production as indicators of upwclling and vertical mixing in
the Indonesian seas. Deep-Sea Res, (in press)
4