Southwest Pacific Ocean Circulation

and Climate Experiment (SPICE)—

Part I. Scientific Background

A. Ganachaud1,2, W. Kessler2, S. Wijffels3, K. Ridgway3, W. Cai3, N.

Holbrook4, M. Bowen5, P. Sutton5, B. Qiu6

, A. Timmermann7, D.

Roemmich8, J. Sprintall8, S. Cravatte1, L. Gourdeau1

, T. Aung9

1Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (LEGOS)/Institut de

Recherche pour le Développement (IRD), Toulouse, FRANCE/Nouméa, NEW CALEDONIA

2National Oceanic and Atmospheric Administration (NOAA)/Pacific Marine Environmental

Laboratory (PMEL), Seattle, WA, USA

3Commonwealth Scientific and Industrial Research Organization (CSIRO)/CSIRO Marine and

Atmospheric Research (CMAR), Hobart/Aspendale, AUSTRALIA

4Department of Physical Geography, Macquarie University, Sydney, AUSTRALIA

5National Institute of Water and Atmospheric Research (NIWA), Wellington, NEW ZEALAND

6School of Ocean and Earth Science and Technology (SOEST), University of Hawaii, Honolulu,

HI, USA

7International Pacific Research Center (IPRC), School of Ocean and Earth Science and Technology (SOEST), University of Hawaii, Honolulu, HI, USA

8Scripps Institution of Oceanography (SIO), San Diego, CA, USA

9University of the South Pacific (USP), Suva, FIJI

CLIVAR Publication Series No. 111

NOAA OAR Special Report

May 2007
NOTICE from NOAA

Mention of a commercial company or product does not constitute an endorsement by

NOAA/OAR. Use of information from this publication concerning proprietary products or the

tests of such products for publicity or advertising purposes is not authorized. Any opinions,

findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration.

This report should be cited as:

Ganachaud, A., W. Kessler, S. Wijffels, K. Ridgway, W. Cai, N. Holbrook, M. Bowen, P. Sutton,

B. Qiu, A. Timmermann, D. Roemmich, J. Sprintall, S. Cravatte, L. Gourdeau, and T. Aung

(2007): Southwest Pacific Ocean Circulation and Climate Experiment (SPICE)—Part I. Scientific Background. International CLIVAR Project Office, CLIVAR Publication Series No. 111,

NOAA OAR Special Report, NOAA/OAR/PMEL, Seattle, WA, 37 pp.

Contribution No. 3070 from NOAA/Pacific Marine Environmental Laboratory

Also available from the National Technical Information Service (NTIS)

(http://www.ntis.gov)

ii
LEGOS—Laboratoire d’Etudes en

Géophysique et Océanographie Spatiales

(www.legos.obs-mip.fr), Institut de

Recherche pour le Développement

(www.ird.fr), Toulouse, France/Nouméa,

New Caledonia (www.ird.nc)

NOAA/PMEL—National Oceanic and

Atmospheric Administration/Pacific

Environmental Laboratory, Seattle, WA,

USA (www.pmel.noaa.gov)

CSIRO/CMAR—Commonwealth Scientific

and Industrial Research Organization/

CSIRO Marine and Atmospheric Research,

Hobart/Aspendale, Australia

(www.cmar.csiro.au)

Department of Physical Geography/

Division of Environmental and Life

Sciences, Macquarie University, Sydney,

Australia (atmos.es.mq.edu.au)

SOEST—School of Ocean and Earth

Science and Technology, University of

Hawaii, Honolulu, HI, USA (www.soest.

hawaii.edu/oceanography/)

IPRC—International Pacific Research

Center, School of Ocean and Earth Science

and Technology, University of Hawaii,

Honolulu, HI, USA

(iprc.soest.hawaii.edu)

SIO—Scripps Institution of Oceanography,

San Diego, CA, USA (sio.ucsd.edu)

NIWA—National Institute of Water and

Atmospheric Research, Wellington, New

Zealand (www.niwascience.co.nz/ncco)

USP—University of the South Pacific, Suva,

Fiji (www.usp.ac.fj)

iii

Contents

1 Rationale 1

2 Objectives 2

3 Scientific Background and Issues 2

3.1 Introduction: The Southwest Pacific Ocean in the Climate System 2

3.2 Main Atmospheric Features: SPCZ and Trade Winds . . . . . . . . 5

3.2.1 SPCZ summary and issues . . . . . . . . . . . . . . . . . . . 7

3.3 Thermocline Water Inflow: Jets and Bifurcation . . . . . . . . . . . 7

3.3.1 Thermocline water inflow summary and issues . . . . . . . 12

3.4 Tasman Sea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4.1 Tasman Sea summary and issues . . . . . . . . . . . . . . . 14

3.5 Gulf of Papua and Solomon Sea . . . . . . . . . . . . . . . . . . . . . 15

3.5.1 Gulf of Papua and Solomon Sea summary and issues . . . 16

3.6 Downscaling and Environmental Impacts . . . . . . . . . . . . . . . 17

3.6.1 SST and climate . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.6.2 Sea level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.6.3 Coral reefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.6.4 Coastal circulation and biodiversity . . . . . . . . . . . . . . 19

3.6.5 Environmental impacts summary and issues . . . . . . . . 20

4 Toward a SPICE Implementation Plan 21

5 Programmatic Context 24

5.1 CLIVAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.2 Regional Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

6 Acknowledgments 25

7 References 26

8 Glossary of Acronyms 35

v

Section 1. Rationale 1

1. Rationale

S

outh Pacific thermocline waters are transported in the westward flowing South Equatorial Current from the subtropical gyre center toward

the southwestern Pacific Ocean—a major circulation pathway that redistributes water from the subtropics to the equator and to the southern ocean.

The transit in the Coral Sea is potentially of great importance to tropical climate

prediction because changes in either the temperature or the amount of water

arriving at the equator have the capability to modulate the El Niño-Southern

Oscillation (ENSO; glossary of acronyms at the end of the document) cycle and

thereby produce basin-scale climate feedbacks. The southern fate of thermocline waters is, comparably, of major influence on Australia and New Zealand’s

climate; its seasonal and interannual evolution influences air-sea heat flux and

atmospheric conditions, and it participates in the combined south Indian and

Pacific Ocean “supergyre.” Substantial changes of this circulation have been

observed over the past 50 years, and are continuing in global climate projections. The subtropical gyre has been spinning up in recent years with possible

consequences for ENSO modulation and for the East Australian Current (EAC),

whose influence has moved south, dramatically affecting the climate and biodiversity of Tasmania.

Despite its apparent importance to the climate system, few observations

are available to diagnose the processes and pathways of transport through the

complicated geography of the southwest Pacific. The South Pacific Convergence Zone is poorly documented; the region is remote, and the large temporal

variability and strong narrow currents in a complex bathymetry pose serious

challenges to an observing system. Numerical model results are sensitive to

parameter choices and forcing, and the results are uncertain because of the

lack of in situ data for validation. The existing observational network (Argo,

VOS XBT sampling, and satellite winds and altimetry) is beginning to provide a

large-scale picture, but the complex circulation and western boundary currents

require further dedicated study. This document lays out the scientific background and identifies the open issues in the southwest Pacific Ocean. Its purpose is to set the basis of a regionally coordinated experiment, the Southwest

PacIfic Ocean Circulation and Climate Experiment (SPICE, http://www.ird.

nc/UR65/SPICE) under the umbrella of the International CLIVAR program (Climate Variability and Prediction, http://www.clivar.org). The corresponding

implementation plan will be developed in a second report, integrating both ob-
2 Ganachaud et al.—SPICE, Part I. Scientific Background

servational and modeling analysis to provide a more complete description of

the mean and variable circulation and climate in the southwest Pacific Ocean.

2. Objectives

The goal of SPICE is to observe, simulate, and understand the role of the

southwest Pacific Ocean circulation in (a) the large-scale, low-frequency

modulation of climate from the Tasman Sea to the equator, and (b) the

generation of local climate signatures whose diagnosis will aid regional sustainable development. This goal will be realized through four specific efforts,

which are discussed in detail in this Scientific Plan:

1. Analysis of the southwest Pacific role in global coupled models;

2. Development of an observational program to survey air-sea fluxes and

currents in the Coral, Solomon, and Tasman Seas, and their inflows and

outflows, with special attention to the strong boundary currents and jets;

3. Combination of these observations with focused modeling efforts to devise a sustained monitoring program to adequately sample the timevariability of the currents and their heat and mass transports;

4. Using remotely and locally sampled meteorological fields, and the ocean

analysis, determination of the air-sea heat and freshwater fluxes and water mass transformations that occur in the region, and their effects on

the local and global climate. A focus here may be the design of a process

study to observe, model, and understand the South Pacific Convergence

Zone.

The simultaneous large-scale and regional approach allows applications

ranging from ENSO forecast improvement, to coral bleaching, cyclone trajectory, or projection of local ocean and climate conditions.

3. Scientific Background and

Issues

3.1 Introduction: The Southwest Pacific Ocean

in the Climate System

The characteristics of the El Niño-Southern Oscillation (ENSO) have

been shown to be sensitive to background oceanic conditions (Fedorov

and Philander, 2001). Those conditions vary on decadal timescales
Section 3. Scientific Background and Issues 3

(Wang and Ropelewski, 1995), with some hypotheses suggesting an influence

of the subtropics. Subtropical-tropical interaction and ENSO modulation has

been debated over the past 10 years, some authors suggesting that ENSO decadal variability was related to the thermocline water inflow (McPhaden and

Zhang, 2002; Schneider, 2004), others that it was caused by atmospheric variability outside the tropics conveyed via the atmosphere (Pierce et al., 2000), or

again by the non-linearities inherent in the coupled equatorial dynamics (Timmermann, 2003). The extra-tropical variability may be transmitted to the Tropics via the ocean (McGregor et al., 2004, 2007) by: (i) changing the temperature

of the water that is advected into the Tropics in the meridional overturning circulation (the vT hypothesis; Gu and Philander, 1997; Zhang et al., 1998); (ii)

changing the rate at which water in the meridional overturning circulation is

advected into the Tropics (the v

T hypothesis; Kleeman et al., 1999; McPhaden

and Zhang, 2002; Nonaka et al., 2002); and (iii) oceanic Rossby waves excited

by variations in the extra-tropical wind stress (Lysne et al., 1997; Liu et al., 1999;

Capotondi and Alexander, 2001; Capotondi et al., 2003; Wang et al., 2003a,b).

Recent numerical and data analyses suggest that the characteristics of

ENSO on decadal timescales mainly originate from the South Pacific (Luo and

Yamagata, 2001; Luo et al., 2003; Luo et al., 2005; Moon et al., 2007), a mechanism involving changes in wind stress patterns and thermocline water transports. It is conceivable that all these effects contribute to determine the characteristics of ENSO, and the coupled, non-linear nature of the system may preclude a rigorous deconvolution. Nevertheless, understanding and modeling

properly the mechanisms that determine the characteristics of the thermocline

waters that emerge within the equatorial cold tongue is of major importance to

all these processes.

Thermocline water pathways are little documented in the subtropical South

Pacific in comparison with those of the subtropical North Pacific. Both the dynamics and geography are fundamentally different between the hemispheres.

To the north, the Inter-Tropical Convergence Zone (ITCZ) inhibits equatorward

flow in the ocean interior (Johnson and McPhaden, 1999) and part of the southward western boundary current leaks into the Indonesian Throughflow. To the

south, where no ITCZ inhibition occurs and most of the equatorial thermocline waters originates, there is a dilemma between a direct (through the ocean

interior) link and an indirect (through western boundary currents) link to the

equatorial region, each having a very different impact on equatorial SST (McCreary and Lu, 1994; Luo and Yamagata, 2001; Giese et al., 2002; Lee and Fukomori, 2003; Fukomori et al., 2004). Observations have also suggested that the

equatorward thermocline transports in the ocean interior have changed in past

decades (McPhaden and Zhang, 2004), but the relative pertinence of interior

and boundary transports remains unknown.

Ocean reanalysis suggests that thermocline waters formed near the center

of the South Pacific subtropical gyre advect spiciness anomalies (i.e., temperature anomalies on isopycnals) to the equator via complex pathways through

the southwest Pacific (Giese et al., 2002). The anomalies, with magnitudes close

to 0.5◦C, are acquired through mixing processes with the surface oceanic layer

(Yeager and Large, 2004) and advect to the equatorial cold tongue in about 10

years (Luo and Yamagata, 2001; Giese et al., 2002). Upon their arrival at the
4 Ganachaud et al.—SPICE, Part I. Scientific Background

equator, these signals have been identified, in some coupled ocean-atmosphere

models, as influential on the amplitude of ENSO (Luo and Yamagata, 2001;

Schneider, 2004; Luo et al., 2005). Some global warming simulations show a

similar mechanism, with greenhouse warming first altering subtropical thermocline waters which then advect toward the equator, thereby influencing

ENSO toward “Niño-like” conditions (Cai and Whetton, 2000). The southern

pathway of thermocline waters fuels the East Australia Current (EAC), the predominant dynamical feature south of 18◦S (Church, 1987). The EAC transports

large quantities of heat energy toward higher latitudes. It separates from the

Australian coast in filaments, giving rise to a region of intense eddy activity

and air-sea exchanges, with marked influence on climate over Australia and

New Zealand (Sprintall et al., 1995; Cai, 2006).

The southwestern Pacific Ocean is therefore the center of major water pathways from the subtropics to the equator and to southern latitudes. Both observational (Tsuchiya, 1981; Tsuchiya et al., 1989) and model tracer studies (Blanke

and Raynaud, 1997; Izumo et al., 2002; Fukumori et al., 2004) suggest that a

substantial fraction of the water arriving at the equatorial cold tongue can be

traced back to the western boundary current system of the South Pacific. Models and observations also suggest that the bulk of the transport feeding the Indonesian Throughflow transits through this region too (Inoue and Welsh, 1993;

Blanke et al., 2002; Talley and Sprintall, 2005). Conversely, the southwest Pacific

has a strong ENSO imprint on its oceanic variations (Holbrook and Bindoff,

1997; Taft and Kessler, 1991; Sutton and Roemmich, 2001; Gouriou and Delcroix, 2002) as well as on its atmospheric variations (Power et al., 1999).

An overriding issue is how inflow from the subtropical gyre is redistributed

meridionally to the equator and to the Tasman Sea as it arrives at the western

boundary. Ocean currents in the southwest Pacific Ocean are impacted by its

complex topography (Fig. 1). Westward-flowing thermocline waters encounter

successively the Fiji plateau; the Vanuatu and New Caledonia Archipelagos; the

Solomon Island Chain; the Australian Coast with the Great Barrier Reef and

Queensland Plateau; New Zealand to the south, the sharp Papua-New Guinea

coastline to the north, and the Solomon Sea with its three narrow north exits: Vitiaz and Solomon Straits and St. Georges Channel. These features cause

narrow boundary currents and jets, with structures and dynamics that are not

properly modeled or sampled.

While basin-scale climate studies point to the southwest Pacific as a region

pivotal to decadal climate variability, neither its oceanic nor atmospheric features have been properly depicted by models or observations, and key aspects

of its climate-important components are not well understood. Those components are, specifically, the main atmospheric feature, the South Pacific Convergence Zone (Section 3.2), the thermocline water pathways and variability

(Section 3.3–3.5), and the local water mass transformations and environmental

impacts (Section 3.6).
Section 3. Scientific Background and Issues 5

3.2 Main Atmospheric Features: SPCZ and Trade

Winds

The southeasterly trade winds dominate the atmospheric circulation in the

South Pacific. Their direction and strength are associated with the South Pacific Convergence Zone (SPCZ), which is noted as “one of the most expansive

and persistent cloud bands” (Fig. 2; see Vincent, 1995, for a review). The SPCZ

is a region of high convective activity associated with strong precipitation, wind

convergence, and diabatic heating (Zhang, 2001). The trade winds in the central South Pacific are substantially affected by its position (Vincent, 1995). The

SPCZ appears to be the dominant convective feature of the Southern hemisphere (Hurell and Vincent, 1987). For Zhang (2001), the Pacific double ITCZ,

and henceforth its lower branch that corresponds to SPCZ, is caused by equatorial westward advection of cold air over the cold tongue that splits the ITCZ

system. For our purposes the remarkable feature of the SPCZ is its southward

bend east of the dateline, causing a diagonal northwest/southeast shape that

distinguishes it from its northern counterpart. This shape has to do with both

SST distribution and the subtropical atmospheric jets, but its presence is not

fully understood (Kiladis et al., 1989; Yoshikane and Kimura, 2003).

The SPCZ position and activity have substantial intraseasonal, seasonal,

and interannual variations. Seasonally, it is most marked in January, when

maximum precipitation extends from New Guinea to 120◦W, 30◦S, following

closely the lines of sea surface temperature and wind convergence maximum

(Kiladis et al., 1989). In July, the SPCZ has a strong zonal portion over the warm

pool near New Guinea and a less marked diagonal portion to the southeast.

On interannual timescales, a northeastward displacement is associated with El

Niño, while a southwest displacement is associated with La Niña. On longer

timescales, its position is affected by the Interdecadal Pacific Oscillation, with

a recent equatorward shift since 1976 (Salinger et al., 2001; Folland et al., 2002).

Locally, the SPCZ has a strong influence on oceanic conditions. On decadal timescales, changes in precipitation and henceforth in the SPCZ position

are measurable in sea surface salinities (Delcroix et al., 2007). The major South

Pacific region of decadal ocean heat content anomalies driven by latent heat

exchanges is located just north of the SPCZ. Those anomalies would then advect to the northwest before joining the equator (Garreau and Battisti, 1999; Yu

and Boer, 2004). The most important decadal changes in thermocline temperature (50–200 m) also occur there, caused by variations in the wind curl (Chang

et al., 2001; Luo and Yamagata, 2001; Cibot et al., 2005).

Many coupled climate models do not reproduce properly the SPCZ and its

variations. Coupled models exhibit a South Pacific convergence zone that extends zonally all the way to the coast of South America, in quasi-symmetry with

the ITCZ north of the equator (e.g., Houghton et al., 2001, p. 480). This results

in overestimation of precipitation in the southeast Pacific and underestimation

in the central and west South Pacific where the observed SPCZ bends to the

south. The model error, though common to almost all coupled general circulation models, is not understood (Li et al., 2004). It may be related to an overestimated equatorial SST gradient and to difficulties in obtaining realistic cloudi-
6 Ganachaud et al.—SPICE, Part I. Scientific Background

Vitiaz St.

 Solomon St. Solomon St.

St. Georges Ch. St. Georges Ch. 

Coral

Sea

Tasman

Sea

Chatham Rise Chatham Rise

Campbell Campbell

Plateau Plateau

Queensland Queensland

Plateau Plateau

Gulf of Gulf of

Papua

Solomon Solomon

Sea

PapuaN. Guinea N. Guinea

Solomon Solomon

Is.

Australia

Fiji

Vanuatu Vanuatu

New

 Caledonia

New 

Tasmania Zealand

Figure 1: Topography of the southwest Pacific.

Figure 2: Left: Observed ERSST (contour) [K] averaged over the period 1954–1974, COADS cloudiness (shading)

averaged from 1960–1970. Right: Simulated time-averaged present-day SST [K] and cloudiness simulated by a

20th-century climate model simulation.
Section 3. Scientific Background and Issues 7

ness off the coast of South America (Wood et al., 2006). One consequence of

the long zonal SPCZ in coupled models is that it does not encompass the kind

of interannual variability of longitudinal position that is in fact observed. This

has unexplored repercussions on air-sea interaction and atmospheric teleconnections between the mid-latitudes and the tropics.

3.2.1 SPCZ summary and issues

The SPCZ is of major influence on the ocean circulation, on the regional climate, and on global climate. Yet, many aspects are not well understood, such

as:

• The formation of the SPCZ;

• Its annual and interannual variability, and the possibility of oceanatmosphere feedback controls;

• The southward veering of the SPCZ east of the dateline, versus the nearzonality of the ITCZ;

• Why global climate models fail to properly reproduce its southward veering (double ITCZ); and what are the consequences on ENSO forecast.

3.3 Thermocline Water Inflow: Jets and

Bifurcation

We now turn to the main water mass that transits through the southwest Pacific

region: the “thermocline” water. Thermocline waters originate from “South Pacific Eastern Subtropical Mode Water” (SPESMW, Hanawa and Talley, 2001) that

forms in the dry and windy center of the southeast Pacific gyre (high salinity

patch on Fig. 3). In this region, water acquires its high salinity and salinity

anomalies through diapycnal mixing due to winter erosion of a strong vertical

salinity gradient, rather than direct subduction (Yeager and Large, 2004; Johnson, 2006). SPESMW is then advected to the west, forming the core of the South

Equatorial Current (SEC, Gouriou and Toole, 1993; Donguy, 1994; Donguy and

Meyers, 1996) with salinities in excess of 36 practical salinity units (PSU). The

SEC carries thermocline waters to the Coral Sea (Fig. 4). Upon its encounter

with the island ridges of Fiji (Stanton et al., 2001), New Caledonia, and Vanuatu,

it divides into three main jets: the South Caledonian Jet (SCJ, 24◦S), the North

Caledonian Jet (NCJ, 18◦S), and the North Vanuatu Jet (NVJ) at 13◦S (Webb,

2000). The NCJ bifurcates on the east coast of Australia, feeding both the EAC

and the New Guinea Coastal Current (NGCC) system. The NGCC supplies the

Equatorial Undercurrent; its properties can be traced to the east Pacific cold

tongue (Tsuchiya et al., 1989). To the south, the EAC flows southward along

the eastern coast of Australia from 18◦ to 35◦S. Its circulation is complicated by

the numerous reefs, deep basins, and ridges that form a complex topography.

The main portion of the EAC separates from the coast at ∼32◦S, much of which

either recirculates northward or flows eastward across the Tasman Sea (as the
8 Ganachaud et al.—SPICE, Part I. Scientific Background

Salinity on isopycnal 25

Figure 3: Salinity on isopycnal σθ = 25 (color) and isopycnal depth (contours) from the Levitus climatology.

σθ = 25 corresponds to the core of the Equatorial Undercurrent (EUC). The white dashed arrow indicates the

main propagation direction of high-salinity waters.

NG

EUC

CUC

S

C

E NVJ

SVJ NCJ NQC

NGCC

EAC

TF EAUC

TO

SCJ

STCC

Figure 4: Integral dynamic height between 0 and 2000 m (m3/s2) from the CARS data. Overlain are the major

current systems of the southwest Pacific. Complex pathways divide the southern part of the South Equatorial

Current (SEC) into jets: North/South Vanuatu Jet (NVJ/SVJ), and South/North Caledonian Jet (NCJ/SCJ). Those

jets feed the western boundary current system: the North Queensland Current (NQC), New Guinea Coastal (Under) Current (NGCC/NGCUC), and, to the south, the East Australian Current (EAC). The northern fate of the

water is the Equatorial Undercurrent (EUC) through the Solomon Straits. The southern fate is the Subtropical

Countercurrent (STCC), the Tasman Front (TF) and the East Auckland Current (EAUC), and the Tasman Outflow

(TO).
Section 3. Scientific Background and Issues 9

Tasman Front). A portion of the Tasman Front reattaches to the northern coast

of New Zealand, forming the East Auckland Current and a sequence of permanent eddies (Ridgway and Dunn, 2003). North of the Tasman Front, a broad,

shallow northeastward flow forms, the Subtropical Countercurrent (STCC). A

remainder of the EAC transport continues southward along the Australian coast

as far as Tasmania and then turns westward into the eastern Indian Ocean as

the Tasman Outflow (Tilburg et al., 2001; Speich et al., 2002).

This circulation is highly variable on a wide range of timescales. At high

frequencies, Qiu and Chen (2004, Fig. 5) identify four regions of high sea surface height variability (equivalent to thermocline displacements): (1) the South

Equatorial Countercurrent, SECC; (2) the EAC; (3) the STCC; and (4) the Antarctic Circumpolar Current (ACC). The observed eddy signals tend to migrate westward as Rossby waves (Maharaj et al., 2005, 2007), accumulating ultimately

along the western boundary of the basin, likely impacting the regional circulation changes in the west on intraseasonal timescales, as well as on longer

timescales through eddy-mean flow interaction. On seasonal timescales, upper ocean observations suggest an important role of local wind curl and remotely forced Rossby waves between 10◦S and 30◦S (Holbrook and Bindoff,

1999, 2000a,b). From a numerical model, Kessler and Gourdeau (2007) found

that the western subtropical gyre responds as a whole to wind changes, spinning up and down. Increased SEC transport in the second half of the year feeds

both the EAC and the NGCC. On interannual timescales, XBT observations suggest a dominant ENSO influence (Ridgway et al., 1993; Holbrook and Bindoff,

1997) with variations in the Solomon Sea leading ENSO. However, the mechanism of these variations remains to be understood. In the North Coral Sea, variations of the main oceanic features, and the island climate, are dominated by

ENSO (Delcroix and Hénin, 1989; Delcroix, 1998), but the main mechanisms by

which those variations are transmitted to the boundary currents and the equator/Tasman Sea remain unresolved. On longer timescales, important changes

are underway: Roemmich et al. (2005) found a strengthening of the subtropical

gyre over the last decade, related to an upward trend of the Southern Annular

Mode (SAM) (Cai et al., 2003), which has been attributed to Antarctic ozone

depletion (Cai, 2006).

In the CARS climatology (Ridgway and Dunn, 2003), the mean westward

geostrophic transport relative to 2000 m of the jets feeding the Coral Sea totals about 35 Sv between New Caledonia and the southern tip of the Solomon

Islands (Fig. 6). At 165◦E, the jets have subsurface maxima from 100 m in the

north to 250 m in the south, with eastward shear above (Reid, 1997; Qu and

Lindstrom, 2002). This structure is a consequence of the general tilt with depth

of the subtropical gyre center (defined as the location where isothermals reach

their deepest point) whose latitude at 160◦W ranges from 14◦S (24◦C, 160 m) to

32◦S (6◦C, 800 m) depth (Fig. 6). Eastward shear weakens or reverses the westward SEC above the local depth of the gyre center. In the vertical integral, the

gyre center in the western Pacific is near 30◦S, but the tilt implies that some

of the eastward recirculation of the gyre occurs as shallow flows north of 30◦S

(Roemmich et al., 2005; Fig. 6). Known as the South Subtropical Countercurrent (STCC, Fig. 6) this eastward surface flow extends to about 15◦S, broken

into filaments by the islands and jets.
10 Ganachaud et al.—SPICE, Part I. Scientific Background

Figure 5: Map of the rms sea surface height variability in the South Pacific Ocean. Based on the combined T/P

and ERS1/2 altimetric data from October 1992 to February 2002. Thick solid lines denote the 0.1-m contour. In

regions above 0.1 m, thin white lines denote contours at a 0.05-m interval (after Qiu and Chen, 2004).

STCC

SEC

SEC

Figure 6: Zonal transport at 160◦W from the CARS climatology. The indicated gyre center line marks the bowl of

the gyre at each isotherm.
Section 3. Scientific Background and Issues 11

Figure 7: Alongshore velocity (cm/s) averaged within 2◦ from the coast. Positive values

are nortwestward, and the contour of zero velocity indicates the bifurcation of the SEC

(after Qu and Lindstom, 2002).

The division of the SEC into jets is principally due to the island arcs (Godfrey’s 1989 island rule), though Kessler and Gourdeau (2006) showed that part

of the jetlike structure is due to the wind itself. The interaction with islands is

assumed to stabilize and enhance jets (Nakano and Hasumi, 2005). The bifurcation of the SEC, roughly at 18◦S along the coast of Australia, separates water

that flows into the equatorial current system from that which recirculates in the

subtropical gyre (Godfrey, 1989; Qu and Lindstrom, 2002; Blanke et al., 2002).

The South Pacific bifurcation is little documented compared with its North Pacific equivalent, and our present understanding is essentially a climatological

description (Qu and Lindstrom, 2002). According to Sverdrup theory, the bifurcation latitude is determined by the zero zonally integrated wind stress curl line

as modified by the Godfrey (1989) “Island Rule” (that shifts its latitude 1◦–2◦ to

the south). However, this simple steady-state, depth-averaged theory is not sufficient to describe the strong spatial and temporal variations in the location of

the bifurcation indicated by models, nor its vertical structure and dependence

on topography. Just as the subtropical gyre circulation varies substantially with

depth, so does the latitude of the bifurcation which is found at 15◦S near the

surface and at 22◦S at 800 m (Fig. 7). The vertical structure is complicated by

the presence of the Queensland plateau at 17◦S, 150◦E (Church and Boland,

1983; Fig. 1). The latitude of the bifurcation also varies substantially with time,

in relation to boundary current and outflow strengths. At the surface, the seasonal variations from a numerical model range range 15◦S to 19◦S (Kessler and

Gourdeau, 2007), showing that on such timescales bifurcation position variations resulted from a basin-scale response of the boundary currents to regional

wind changes.

In most published numerical experiments, the mean position of the bifurcation latitude is too far to the north (e.g., Luo et al., 2005) because of its high

sensitivity to key parameters such as the Indonesian Throughflow (Hirst and
12 Ganachaud et al.—SPICE, Part I. Scientific Background

Godfrey, 1993) and possibly the flow through the Solomon Straits. The longitudinal distribution of western boundary current transport to the equator is

sensitive to the details of the bathymetry of the narrow straits that bound the

northern Solomon Sea, and properly representing these features in models is

an ongoing subject of research.

3.3.1 Thermocline water inflow summary and issues

The dynamics of the jets and bifurcation need further understanding. We propose here to address the following issues in the SPICE context:

• The jet formation, variability, and characteristics;

• The transit in the Coral Sea and the dynamics of the bifurcation, especially on timescales longer than seasonal;

• Variability sources such as ENSO teleconnections, Rossby waves, forced

by basin-wide winds and circulation around Australia;

• The role of the NCJ in the north-south distribution of SEC waters versus

the role of the bathymetry in the vicinity of the Queensland Plateau;

• The relationship of the bifurcation latitude and vertical structure with the

inflow and the outflow streams of the Coral Sea.

3.4 Tasman Sea

The EAC provides both the western boundary of the South Pacific Gyre and

the linking element between the Pacific and Indian Ocean gyres. Climatology

shows that the current is accelerated southward along the coastal boundary

and then separates into northeastward (STCC), eastward (Tasman Front) and

residual southward (Tasman Outflow) components (Fig. 8). Between 18◦S and

35◦S the southward transport in the EAC ranges from 25 to 37 Sv, the latter

value including a significant recirculation feature. A western boundary current

forms along the northeastern coast of New Zealand and consists of the East

Auckland Current (EAUC), the East Cape Current, and a series of persistent eddies (Fig. 8). Southward transport in the EAUC is highly variable, with a mean

of about 9 Sv (Stanton and Sutton, 2003). In the interior of the Tasman Sea,

south of the Tasman Front, flow is generally westward and weak (Chiswell and

Rickard, 2006). The subtropical front crosses the south edge of the Tasman Sea

and is found close to the southern and southwestern coasts of New Zealand

before turning east over Chatham Rise (Sutton, 2001; Chiswell, 2005). On the

western side of the Tasman Sea, the residual Tasman Outflow turns west south

of Tasmania, and joins the South Indian subtropical gyre, thereby playing a significant role in the global thermohaline circulation (Speich et al., 2002).

Surprisingly few modeling studies have focused on the dynamics of the EAC

and EAUC. Tilburg et al. (2001, 2002) suggested, from a numerical model, that

gradients in wind stress curl control the separation locations while non-linear
Section 3. Scientific Background and Issues 13

20

25

30

35

40

45

150 160 170 180

WE

STF

SC

Chatham 

Rise

TF

TO

EAC

EAUC

ECC

STCC

Figure 8: A schematic summary of the EAC and its outflows in the Tasman Sea

(adapted from Ridgway and Dunn, 2003). STCC stands for South Tropical Countercurrent, TF for Tasman Front, EAUC for East Auckland Current, ECC for East Cape Current,

WE for Wairarapa Eddy, STF for SubTropical Front, and TO for Tasman Outflow. The

thick dotted lines delineate the “Tasman box” high resolution XBT lines.

dynamics induce the meanders. The quasi-permanent character of the baroclinic eddies would be associated with a “topographic coupling” between the

upper and abyssal ocean. However, in the Tilburg et al. model, the EAC variability and the southward outflows were far from realistic. The EAC demonstrates a

strong seasonal cycle with maximum alongshore flow in the summer (Ridgway

and Godfrey, 1997), and the origin of this seasonality is not well understood.

The variability is indeed as large as the mean flow, with a 30 Sv-rms variability

for a 22 Sv mean transport at 30◦S (Mata et al., 2000). The region of highest surface variability lies above an abyssal cul-de-sac basin adjacent to the western

boundary. Much of this variability arises from the production and propagation

of mesoscale eddies whose trajectories follow complex patterns that resonate

within the deep basin at periods of 100 and 150 days. The origins of the eddies

is not clearly understood, those being either generated by strong local instability or controlled by remotely forced Rossby waves from the eastern Pacific

(Bowen et al., 2005; Ridgway, 2006).

At the Tasman Sea basin scale, there is considerable interannual variability of the upper ocean temperature field, including ENSO timescale variations

(Holbrook and Bindoff, 1997; Holbrook et al., 2005). Such variations are also

observed in mode water formation rates (Holbrook and Maharaj, 2007) and in
14 Ganachaud et al.—SPICE, Part I. Scientific Background

integral heat content (Roemmich et al., 2005). Cai (2006) shows that an observed poleward displacement of the westerly wind maximum has increased

the strength of the subtropical gyre and produced an increase in the southward flow of the EAC into the Tasman Sea. The consequence of this shift is an

increase in the EAC flow into the Tasman Sea (Cai, 2006), affecting the heat balance. This spin-up of the gyre has been observed on the eastern side of New

Zealand (Roemmich et al., 2007), but the present EAC monitoring does not allow us to fully understand the associated changes in the Tasman Sea and their

relation with heat balance variability, especially on interannual timescales.

3.4.1 Tasman Sea summary and issues

• The circulation and water mass transports through the Tasman Sea need

to be established by determining robust estimates of the mean and seasonal cycle of each inflow and outflow component and identifying the

source, strength, property variability, and pathways of the major water

masses. The mechanisms associated with features such as current separation and reattachment, location of semi-permanent eddies, retroflection, and the partitioning of the flow needs a comprehensive, quantitative description. The EAC is highly variable and dominated by eddies, but

the formation mechanism needs to be understood. Are eddies generated

by local forcing or are they entering the region from the east? How do eddies interact with the mean flow and topography? An appropriate theory

needs to be developed.

• From a large-scale perspective, the partition of the western boundary

flow between the Pacific and Indian Ocean gyres is of major interest.

Understanding this partition requires determining the mean and timevarying components of the EAC, the Tasman Front, STCC, and the Tasman Outflow, their variations on interannual to decadal timescales, and

the effects of anthropogenic change. How are climate-change-related variations in gyre transport and density structure communicated through the

western boundary via the EAC?

• The Tasman Sea heat balance also requires specific studies. As Kelly (2004)

shows for the North Pacific, the western, poleward area of the subtropical gyre is one of important transit of heat from the tropics and to the

mid-latitude atmosphere. While recent studies in the Tasman Sea have

indicated that ocean advection processes are important for the region

(Roemmich et al., 2005), the relative contributions of advection and heat

storage compared to the surface heat flux are poorly understood, especially on interannual to decadal timescales. We need an improved understanding of the heat flux components, particularly their variability and

how heat is partitioned between the atmospheric fluxes and recirculated

within the gyre.
Section 3. Scientific Background and Issues 15

3.5 Gulf of Papua and Solomon Sea

The Solomon Sea is both a choke point and the location of intense and interleaved boundary currents that foster mixing of the thermocline waters that

feed the EUC and, eventually, the equatorial cold tongue. The partition of these

water masses among the three straits determines the thermocline water route

to the equator (the longitude at which it joins the EUC), with potential consequences for the equatorial response to changes in the South Pacific winds and

circulation.

The pioneering WEPOCS cruises of 1985–1986 (Lindstrom et al., 1987) provided important snapshots of the tropical end of the South Pacific western

boundary current system, but observations in the Coral Sea consist of scattered surveys that only sketch the large-scale mean flows. The CARS climatology suggests that SEC waters use two pathways to reach the Solomon and

Vitiaz Straits (Fig. 9): one coming from the NCJ, bifurcating against the Australian coast near 18◦S to form the North Queensland Current (NQC); another

more direct pathway flowing between the northern Vanuatu region (10◦S–15◦S)

and the center of the Solomon Sea. The NQC first accomplishes a 200◦ cyclonic

turn in the Gulf of Papua to reach the eastern tip of the Louisiades Archipelago;

it then steers north to cross the Solomon Sea, presumably against the western

boundary—implying a U-turn on the Louisiades Archipelago tip (as suggested

by available shipboard ADCP data), to reach the three northern outflows which

are Vitiaz Strait, St. Georges Channel, and Solomon Strait. Observations suggest

northward transports in Vitiaz Strait (8 to 14 Sv) and St. Georges Channel (4 to 7

Sv), with currents of order 1 m/s (Lindstrom et al., 1990) and large interannual

variations (Ridgway et al., 1993). North of the straits, about half the thermocline water (σ = 24.5 to σ = 26.5) flows in the NGCU and the other half in the

New Ireland Coastal Undercurrent (Butt and Lindstrom, 1994). Both currents

eventually join the EUC, each one using a different pathway (Butt and Lindstrom, 1994). South of the WEPOCS area (9◦S), the only existing full-depth, synoptic meridional section across the Coral and Tasman Seas was the WOCE P11

line along 154◦E–156◦E from the tip of New Guinea, south to 43◦S during June–

July 1993 (Sokolov and Rintoul, 2000). Taking geostrophic velocities relative to

the bottom, they estimated the transport of the SEC across this section to be

55 Sv, balanced almost equally by flow northward into the Solomon Sea via the

NGCC (26 Sv) and southward into the EAC (28 Sv). These single-realization

transports are about 30% larger than those indicated by climatology.

Neither the thermocline water inflow nor the outflow through the straits are

well documented, nor is the circulation within the Solomon Sea. Long-term

observations in the region are sparse, and the Argo float array does not sample this enclosed area well because of the fast flow around the numerous small

islands and passages. Climatologies are hampered by the very low data coverage, and most of the present knowledge comes from WEPOCS that covered the

northern part of the Solomon Sea and the Straits. Because the straits are narrow (Vitiaz Strait and St. Georges Channel are narrower than 50 km at 500 m

depth), published numerical models do not properly resolve flow, constraining

the thermocline water to exit the Solomon Sea to the east with unknown conse-
16 Ganachaud et al.—SPICE, Part I. Scientific Background

Figure 9: Climatological circulation at 200 m depth (CARS climatology).

quences on the total transport and timing between the bifurcation region and

the EUC formation region. The presence of highly energetic boundary currents

and their encounter with the broader SEC from the east makes the Solomon

Sea a potential region of high mixing and water mass transformation.

3.5.1 Gulf of Papua and Solomon Sea summary and issues

The whole region is very poorly described. In the SPICE context, there is an

urgent need to better understand:

• The characteristics and transports of waters transiting through the Solomon Sea. Specifically, the partitioning between the Vitiaz Strait/Solomon

Strait/St. Georges Channel transport over seasonal-to-interannual timescales;

• The respective contribution of the western boundary current and of the

direct flow from the SEC to the east Solomon Sea, as indicated by climatology (Fig. 9);

• Potentially important details of the circulation, including the permanent

eddies suggested by numerical modeling, and possible flows through topographic gaps between islands;
Section 3. Scientific Background and Issues 17

• Local versus remote influences on the western boundary current structure (wind-driven surface currents; basin-scale undercurrents);

• Water mass transformations.

3.6 Downscaling and Environmental Impacts

Downscaling is here defined as the transition from large scales to small scales,

including island scales and coastal circulation scales. Southwest Pacific countries are particularly sensitive to climate variability and the oceanic environment. Freshwater resources are a critical issue for Australia and vary substantially in relation with ENSO and decadal variability (Power et al., 1999). The

Island Nations of the southwest Pacific Ocean are often isolated, low-lying, and

densely populated, and highly dependent on their oceanic environment. As

direct consequences of global warming, the projected sea level rise, as well

as the predicted changes in the occurrence and magnitude of extreme events,

could have devastating social and economic consequences (e.g., http://www.

islandvulnerability.org). However, global climate models have relatively

coarse atmospheric and oceanic grids so that climate changes in small-scale

ecosystems are not very well understood. The ocean locally has an important influence on the climate and environment by its ability to transport large

amounts of heat, controlling the temperature and air-sea fluxes, tropical cyclone intensity and trajectories, and transports of fish larvae. The following

sections give a synopsis of the different aspects of ocean and climate impacts

in the southwest Pacific.

3.6.1 SST and climate

A base of knowledge on ocean heat transports and exchanges in the Tasman

Sea has been gained by monitoring the inflows and outflows along commercial shipping routes. In the southwest Tasman Sea a warming of 0.015◦C yr−1

between 1955 and 1988 has been observed in the upper 100 m, representing

a contribution to sea level rise, through thermal expansion, of about 0.3 mm

yr−1 (Holbrook and Bindoff, 1997; Pittock et al., 2001). In the “Tasman Box,”

as defined in Fig. 8, the regularly repeated measurements over 12 years suggest

that the advective ocean heat transport convergence was driving air-sea fluxes

(Roemmich et al., 2007). Sprintall et al. (1995) identified those fluctuations as

the cause of the 1992 New Zealand coldest winter on record. More recently,

heat content in the Tasman Sea rose markedly in 1998 before falling several

years later (Willis et al., 2004; Sutton et al., 2005). The increased ocean temperatures may have led to an increase in New Zealand’s land temperatures (Sutton

et al., 2005; see also Basher and Thompson, 1996).

Along the Australian east coast between southern Queensland and Tasmania, intense low pressure systems known as the “east coast lows” develop (Holland et al., 1987; Hopkins and Holland, 1997). With destructive potential close

to that of tropical cyclones, they can blossom in a day or so, drawing moisture from the warm waters of the Tasman Sea and producing intense, flooding
18 Ganachaud et al.—SPICE, Part I. Scientific Background

rains, wind damage, storm surges, beach erosion, and marine accidents. The

observed Tasman Sea warming (Holbrook and Bindoff, 1997; Cai, 2006), which

is expected to continue under greenhouse conditions (Cai et al., 2005), is conducive to the genesis of east coast lows. A detailed assessment of how their

intensity and frequency will change in response to the Tasman Sea warming is

needed.

To the north, climate in the Pacific Island Nations (PINs) is dominated by

the position of the SPCZ, which is itself modulated by ENSO and decadal variability (Salinger et al., 2001; Griffiths et al., 2003). The ocean component may

be, as for the Tasman Sea, an important contributor to regional climate (see

Section 3.2), the local oceanic conditions influencing cloudiness and winds

(e.g., cold upwelling water modifying land-sea temperature gradients). Understanding the present and future climate in PINs will require detailed knowledge

of the ocean and atmosphere on small scales, making use of regional, highresolution climate models embedded in global climate projections.

PINs are among the most vulnerable countries to tropical cyclones (Pelling

and Uitto, 2001). Tropical cyclones develop on a regular basis in the southwest

Pacific Summer. The upper ocean heat content and background atmospheric

conditions are of major influence on their incidence, trajectories, and impacts

(Basher and Zheng, 1995; McDonnell and Holbrook, 2004a,b). The destructiveness of tropical cyclones has been increasing over the past 30 years, and there

is a debated possibility of continued increase associated with global warming

(Emanuel, 2005; Webster et al., 2005). The upper ocean is part of a tropical

cyclone system. To predict tropical cyclone trajectories and intensity, not only

the SST and upper ocean heat content need to be determined on fine scales,

but because there are dynamical and thermodynamical feedbacks between the

ocean and the atmosphere, a coupled model approach is also necessary.

3.6.2 Sea level

IPCC reports a projected mean sea level rise up to 5 mm/yr (McCarty et al.,

2001, p. 845). This is subject to debate and new estimates modify this value

(e.g., Overpeck et al., 2006). At a given location, the effective sea level can undergo much larger variations from ocean circulation changes, either naturally

or anthropogenically induced. Besides tides, the main component is the thermosteric one, induced by changes in upper-ocean temperature. Over the past

10 years (1993–2003), Willis et al. (2004) found substantial changes in the thermosteric component from shifts in the gyre circulation (Roemmich et al., 2005;

Qiu and Chen, 2006), with strong spatial variations which, in the southwest Pacific, imply a sea level fall (from 25◦S to 32◦S) or rise (north and south of this

latitude band) of order 10 cm, a result that is related to the large-scale spin

up of the South Pacific Gyre reported by Roemmich et al. (2005). Lyman et al.

(2006) noticed, since 2003, and in our region of interest, a thermosteric sea level

fall of about 10 cm between 15◦S and 30◦S as well as along the EAC path, and

warming elsewhere with up to 10 cm rise in the Tasman Sea. Those fluctuations

need to be better understood, as they can temporarily obstruct longer-term signals.
Section 3. Scientific Background and Issues 19

On shorter timescales of a few weeks, oceanic eddies dominate the sea level

signal. A warm eddy with a radius ranging from 20 km (at 40◦S) to 100 km

(at 10◦S; Chelton et al., 1998) can raise the sea level by order 10 cm (Fig. 5),

while a cold eddy would lower it by the same amount. Constructive addition

of the large-scale changes, an oceanic eddy with high tide, and a storm surge

can have disastrous consequences. Understanding and, if possible, predicting

those components may moderate the impact, and requires a detailed knowledge of the ocean circulation at fine scales.

3.6.3 Coral reefs

Coral reefs, which constitute the most important natural resource as well as a

natural shield against storm surges in many islands, are under serious threat.

The IPCC reports that “the combination of anthropogenic pressure, ocean acidification and increased temperature maxima severely affect the reef’s ability to

keep pace with sea level rise” (McCarty et al., 2001, 17.2.4). Some reef-building

species have narrow temperature tolerances and live near their limits. Major

bleaching events occur for temperatures exceeding their average summer maximum by 1◦C—a limit that will be overreached for about 60% of the world reefs

over the next two decades (McCarty et al., 2001, 17.2.4). The 1997–1998 ENSO

event caused 90% bleaching in some regions, providing an estimate of the potential effect of future warming (McCarty et al., 2001, 6.4.5). Coral reef health is

studied and monitored within specific programs (e.g., UNESCO-funded Coral

Reef Initiative in the South Pacific program, http://www.crisponline.net;

Great Barrier Reef management at AIMS, http://www.aims.gov.au). Those

programs will benefit from an improved knowledge of temperature and sea

level changes associated with changes in the ocean circulation, from the basin

scale to the island scale and on monthly to decadal timescales.

3.6.4 Coastal circulation and biodiversity

The ocean currents along coastlines, barriers, and islands have various impacts on the oceanic ecosystem, besides the special case of coral discussed

above. The growth rate of many organisms is sensitive to changes in temperature, while the reproduction cycle often involves ocean transports of fish larvae. The southwest Pacific currents result from complex interactions between

large-scale currents and the numerous islands and ridges. Ocean impacts on

ecosystems fall in two main categories: island effects and boundary-current

variations.

Island effects. Southwest Pacific islands are mostly surrounded by steep

ocean bottom slopes that locally modify the large-scale physical and chemical

ocean properties, depending on their configuration with respect to the main

ocean currents and atmospheric winds. Island effects are disparate (e.g., http:

//www.islandoceanography.org): in Palau (Micronesia), internal tides produce upwelling (Wolanski et al., 2004); while west of Hawaii, an eastward flow is

generated against the main current (Qiu and Durland, 2002). In the Marquesas

Islands (south central Pacific), the modification of the SEC flow triggers phy-
20 Ganachaud et al.—SPICE, Part I. Scientific Background

toplankton blooms (Martinez and Maamaatuaiahutapu, 2004). In New Caledonia, the shelf is “felt” by the large-scale ocean dynamics like a 750-km line

obstacle oriented SE-NW, as are the dominant trade winds. This configuration

leads to the formation of boundary currents on the eastern side, and to an omnipresent upwelling on the western side (Fig. 10). This upwelling lowers the average ocean temperature on the west coast by about 2◦ (Alory et al., 2006), with

an unevaluated influence on the lagoon ecosystem and tropical cyclone trajectories. The consequences of island effects and associated biogeochemistry can

be substantial, and southwest Pacific islands are very little documented.

Islands, because of their topography and/or albedo, also have a strong local

influence on large-scale winds and cloud cover. This combines with the local

SST to modulate land-sea temperature contrasts and associated winds. Conversely, modified coastal winds alter the ocean circulation (e.g., the intensity of

an upwelling). A full understanding of the ocean-atmosphere variations, therefore, requires a coupled ocean-atmosphere approach.

Boundary-current impacts. Changes in boundary currents such as the EAC

and EAUC (Fig. 8) are dynamically different from the island effects discussed

above. The increase in temperatures in the EAC system associated with the

subtropical gyre spin-up has modified the Tasmanian ecosystem with the appearance of twenty new species (Cai et al., 2005, and references therein). This

same increase is suspected to have reduced the food supply for juvenile fish

in the Tasman Sea (Bradford-Grieve et al., 2005). The EAC has a major impact

on the shelf circulation and ecosystem south of 20◦S, with its seasonal cycle

producing strong currents (Huyer et al., 1988; Ridgway and Godfrey, 1997). Interaction of the EAC and its eddies with local topography and wind forcing also

contribute to upwelling processes (Rochford, 1975; Gibbs et al., 1998; Oke and

Middleton, 2001). East of New Zealand, the EAUC variability is spread over a

wide range of frequencies (Stanton and Sutton, 2003) and its fluctuations contribute to harmful algal blooms (Sharples, 1997) and may also induce localized upwelling along the coast (Sharples and Greig, 1998). The EAUC is part

of the lobster reproduction cycles, with its semi-permanent eddies along the

east coast of the North Island retaining the larvae near the coast during their

planktonic stage (Chiswell and Booth, 1999). In the North Coral Sea, including

the Gulf of Papua and Solomon Sea, a substantial oceanic influence is foreseeable, given the strong boundary currents and their variations (Lindstrom et al.,

1990). Nevertheless, this is a region where a basic knowledge of the structure

and dynamics of the currents needs to be established, as discussed in Section

3.5.

3.6.5 Environmental impacts summary and issues

The ocean circulation and biogeochemical properties are poorly known near

most Pacific Island nations. How does the large-scale ocean circulation interact with regional climate and circulation near the Pacific Islands? How does the

ocean circulation and its variations affect ecosystems and populations? How

will climate change influence these systems? These three questions are of major concern to all southwest Pacific nations. The coastal waters of eastern Aus-
Section 4. Toward a SPICE Implementation Plan 21

tralia and New Zealand are better understood for having been studied for several decades, but many aspects still remain unexplored. Climate change and

projected ocean circulation changes will have a strong, potentially dramatic

impact on the southwest Pacific countries. Societal and environmental aspects

of this impact are addressed within specific programs, and we propose within

SPICE to tackle their oceanic and atmospheric components. We identified a

number of sensitive issues, including:

1. Downscaling of projected global climate change;

2. Coral reef sustainability: variations of SST and SSH on timescales from

weeks (SST, SSH) to decades (SSH);

3. Small-scale oceanic circulation around islands: the effect on ecosystem,

local climate, and cyclones;

4. Impact of cyclone surge: background SSH variations over weekly timescales;

5. Large-scale gyre spin-up: effect on New Zealand and southeast Australian

climate and ecosystems.

4. Toward a SPICE

Implementation Plan

This first of two reports formulates the main issues of the southwest

Pacific Ocean and its relation to local and remote climate. The second

report will propose a coordinated study of the circulation of the southwest Pacific to address these in a collaborative and cost-effective approach

based on existing human and technical resources.

SPICE is regionally focused, but designed within the basin-scale

ocean-atmosphere system. The large-scale context, including the basin-scale

South Pacific circulation and its connection with equatorial processes and climate variability, are addressed within other CLIVAR experiments. The priorities

that are specific to SPICE are summarized in Fig. 11.

The following institutions have expressed interest in contributing to specific aspects of SPICE, given funding opportunities:

1. LEGOS-Toulouse (http://www.legos.obs-mip.fr, and its New Caledonia branch at IRD (http://www.ird.nc), Noumea; numerical modeling and seagoing facilities; 28-m Research Vessel (RV) and possibilities

for using French National Fleet RVs (http://www.ifremer.fr/flotte/

navires); XBT and thermosalinograph network management).

2. NOAA/PMEL (http://www.pmel.noaa.gov, Seattle, WA, USA, theoretical, glider data analysis, and XBT expertise).
22 Ganachaud et al.—SPICE, Part I. Scientific Background

Figure 10: SST image of the southern part of New Caledonia during an upwelling event (A. Vega, P. Marchesiello,

J. Lefèvre, and A. Ganachaud, Coastal upwelling modulated by island wake effect off New Caledonia, personal

communication, 2007).

SPICE 

North Coral Sea: issues

WBC and Straits

Thermocline 

water

formation

Link to the Equator and ENSO modulation

SEC inflow:

Jets and Bifurcation

Heat transports

EAC/EAUC:

Variability and air-sea fluxes

Local and regional

oceanic impacts

Figure 11: Main issues addressed within SPICE, in addition to the SPCZ caveat. Thermocline water formation

and junction to the Equator are addressed within larger-scale programs.
Section 4. Toward a SPICE Implementation Plan 23

3. CSIRO-Hobart (http://www.cmar.csiro.au, Hobart: numerical modeling and seagoing facilities; 66 m RV Southern Surveyor; state-of-the-art

ocean reanalysis system with a domain that includes the whole of the

Indo-Pacific; XBT, and Argo data analysis center).

4. CSIRO-Melbourne (http://www.cmar.csiro.au, Melbourne: advanced

global climate model; Regional Atmospheric Models).

5. NIWA (http://www.niwascience.co.nz/ncco, Wellington, New Zealand: numerical modeling and sea going facilities; 70 m RV Tangaroa,

28 m RV Kaharoa; XBT and Argo support; regional modeling using ROMS,

MOMA, Gerris, RiCom).

6. University of Hawaii (http://www.soest.hawaii.edu/oceanography/,

Honolulu: analysis and interpretations of satellite altimetrically derived

sea surface height data in conjunction with in situ observational data and

numerical model output).

7. SIO (http://sio.ucsd.edu, San Diego, CA: expertise in using floats, gliders, hydrography, moorings, and data assimilating models).

8. Macquarie University (http://www.mq.edu.au/, Sydney, Australia: analysis and interpretation of satellite altimeter sea surface height data; in

situ ocean data analysis; reduced-gravity ocean modeling and continuously stratified (multi-mode) ocean modeling; climate analysis and climate modeling).

9. Bureau of Meteorology (http://www.bom.gov.au/bmrc/ocean/index.

htm, Melbourne, Australia: Ocean and marine forecasting, research, and

operational data assimilation, seasonal prediction, real-time networks

(weather stations, including buoys, VOS SST observations, tide gauges)).

10. SOPAC (www.sopac.org.fj), the South Pacific Applied Geoscience Commission, is an inter-governmental regional organization “dedicated to providing services to promote sustainable development in the countries it

serves.” Research, development, and management of the oceanic environment is one of SOPAC’s key programs. A component of this program

is the Pacific Islands Global Ocean Observing System, PI-GOOS (http://

www.sopac.org.fj/tiki/tiki-index.php?page= PIGOOS), aimed at

developing capacity in operational oceanography in the Pacific region.
24 Ganachaud et al.—SPICE, Part I. Scientific Background

5. Programmatic Context

5.1 CLIVAR

CLIVAR (http://www.clivar.org) is the World Climate Research Programme (http://wrcp.wmo.int) project that addresses climate variability and predictability. CLIVAR is focused on the role of oceanatmosphere interactions in climate. It aims at developing our understanding of

the physical processes responsible for climate modulation on seasonal, interannual, decadal, and centennial timescales. This objective requires monitoring

ongoing changes in our climate system. The work points toward an extension

of the range and accuracy of predictions to provide useful information so that

governments can make informed decisions about societal impacts.

SPICE has been built to contribute to the CLIVAR objectives, with a largescale approach targeted toward decadal climate prediction through a better understanding and modeling of the equatorial and southwest Pacific Ocean circulation, and an embedded smaller-scale objective targeted toward coastal and

island climate processes and prediction. There is a particular focus here on

western boundary currents, which are recognized as a key issue by CLIVAR because they accomplish a large and rapid meridional transport of mass and heat.

Though the southwest Pacific boundary currents are less studied than in other

parts of the world, they are of special interest for climate because they provide

an efficient communication from the subtropical gyre to the equator.

In SPICE we take the first steps toward implementing the observations necessary to interpret the southwest Pacific circulation and its effects on local and

remote climate, and to build a regional observing system that will allow ongoing monitoring of its variability. This effort follows the philosophy of the

US-CLIVAR Pacific Basin Extended Climate Study (PBECS; Kessler et al., 2001;

Davis et al., 2000; Lukas et al., 1998) which was an early effort to frame the

problem of observing and interpreting the climate of the Pacific basin. The

PBECS view was that the basin-scale observing network (Argo, satellite observations, TAO moorings, ship-of-opportunity cruises) could adequately resolve

the broad interior flows, but that special attention would be needed to sample

the boundaries (including the surface layer and the equatorial current system

and its intimate interaction with the atmosphere).

5.2 Regional Programs

• The PACific Source Water Investigation (PACSWIN) is currently being designed as a follow-up of the International Nusantara Stratification and

Transport (INSTANT) program (http://www.esr.org/instant_index.
Section 6. Acknowledgments 25

html) on the Indonesian Throughflow. The PACSWIN plan is to extend

the INSTANT region of interest, including the Coral Sea, to better resolve

origins and fates of water masses crossing the Indonesian Seas (P.I.J. You,

University of Sydney, Institute of Marine Science).

SPICE will establish the link between large-scale ocean currents and coastal/

island circulation in collaboration with the following programs that concern

the Pacific Island Countries:

• SOPAC, see Section 4.

• PRIDE (http://apdrc.soest.hawaii.edu/PRIDE), Pacific Region Integrated Data Enterprise; aims at providing regional needs for ocean, climate, and ecosystem information to protect lives and property, support

economic development, and enhance the resilience of Pacific Island communities in the face of changing environmental conditions.

• SPREP (http://www.sprep.org), Pacific Regional Environment Programme; focus on sustainable planning, protection, management, and

use of Pacific Island environment.

• START-Oceania (http://www.usp.ac.fj/start), capacity building in

the domain of impacts of climate change research.

6. Acknowledgments

The concept of a coordinated experiment in the southwest Pacific

emerged during a workshop in August 2005 in Malanda, Australia, cosponsored by the Institut de Recherche pour le Développement and the

French Pacific Funds. AG thanks NOAA’s Pacific Marine Environmental Laboratory and its director, Dr. Eddie Bernard, for hosting him during the writing of

this document, and the NOAA PRIDE program led by Howard Diamond, which

helped support the visit. This document benefited from valuable comments

and insights by S. Behera, G. Brassington, R. Davis, T. Delcroix, G. Eldin, J. Luo,

C. Maes, P. Marchesiello, T. Qu, B. Timbal, T. Tozuka, M. Williams, and T. Yamagata. We are grateful to K. Birchfield, R.L. Whitney, and T. Nakamura of PMEL

for their help with figures and editing.
26 Ganachaud et al.—SPICE, Part I. Scientific Background

7. References

Alory, G., A. Vega, A. Ganachaud, and M. Despinoy (2006): Influence of upwelling, subsurface stratification, and heat fluxes on coastal sea surface

temperature off southwestern New Caledonia. J. Geophys. Res., 111, C07023,

doi: 10.1029/2005JC003401.

Basher, R.E., and C.S. Thompson (1996): Relationships of air temperature in

New Zealand to regional anomalies in sea surface temperature and atmospheric circulation. Int. J. Climatol., 16, 405–425.

Basher R., and X. Zheng (1995): Tropical cyclones in the Southwest Pacific: Spatial patterns and relationships to the Southern Oscillation and sea surface

temperature. J. Climate, 8, 1249–1260.

Blanke, B., and S. Raynaud (1997): Kinematics of the Pacific equatorial undercurrent: An Eulerian and Lagrangian approach from GCM results. J. Phys.

Oceanogr., 27, 1038–1053.

Blanke, B., S. Speich, G. Madec, and R. Maugé (2002): A global diagnostic of interior ocean ventilation. Geophys. Res. Lett., 29(8), 1267, doi: 10.1029/2001

GL013727.

Bowen, M., J. Wilkin, and W. Emery (2005): Variability and forcing of the East

Australian Current. J. Geophys. Res., 110, C03019, doi: 10.1029/

2004JC002533.

Bradford-Grieve, J., M. Livingston, P. Sutton, and M. Hadfield (2004): Fisheries

Oceanography: Ocean variability and hoki decline. Water Atmos., 12(4),

20–21.

Butt, J., and E. Lindstrom (1994): Currents off the east coast of New Ireland,

Papua New Guinea, and their relevance to regional undercurrents in the

western equatorial Pacific Ocean. J. Geophys. Res., 99(C6), 12,503–12,514.

Cai, W.J. (2006): Antarctic ozone depletion causes an intensification of the

southern ocean supergyre circulation. Geophys. Res. Lett., 33, L03712,

doi: 10.1029/2005GL024911.

Cai, W.J., G. Shi, T. Cowan, D. Bi, and J. Ribbe (2005): The response of southern

annular mode, the East Asutralian Current, and the southern midlatitude

ocean circulation to global warming. Geophys. Res. Lett., 32, L23706, doi:

10.1029/2005GL024701.

Cai, W.J., and P.H. Whetton (2000): Evidence for a time-varying pattern of greenhouse warming in the Pacific Ocean. Geophys. Res. Lett., 27(16), 2577–2580.

Cai, W.J., P.H. Whetton, and D.J. Karoly (2003): The response of the Antarctic

oscillation to increasing and stabilized atmospheric CO2. J. Climate, 16(10),

1525–1538.

Capotondi, A., and M.A. Alexander (2001): Rossby waves in the tropical Pacific

and their role in decadal thermocline variability. J. Phys. Oceanogr., 31(12),

3496–3515.
Section 7. References 27

Capotondi, A., M.A. Alexander, and C. Deser (2003): Why are there Rossby wave

maxima in the Pacific at 10◦S and 13◦N? J. Phys. Oceanogr., 33(8), 1549–

1563.

Chang, P., B. Giese, L. Ji, H. Seidel, and F. Wang (2001): Decadal change in the

south tropical Pacific in a global assimilation analysis. Geophys. Res. Lett.,

28(18), 3461–3464.

Chelton, D., R. deSzoeke, M. Schlax, K. El Naggar, and N. Siwertz (1998): Geographical variability of the first-baroclinic Rossby radius of deformation. J.

Phys. Oceanogr., 28(3), 433–460.

Chiswell, S.M. (2005): Mean and variability in the Wairarapa and Hikurangi Eddies, New Zealand. N.Z.J. Mar. Freshw. Res., 39, 121–134.

Chiswell, S.M., and J.D. Booth (1999): Rock lobster Jasus edwardsii larval retention by the Wairarapa Eddy off New Zealand. Mar. Ecol. Prog. Ser., 183,

227–240.

Chiswell, S.M., and G.J. Rickard (2006): Comparison of model and observational ocean circulation climatologies for the New Zealand region. J. Geophys. Res., 111, C10011, 10.1029/2006JC003489.

Church, J.A. (1987): East Australian Current adjacent to the Great Barrier Reef.

Aust. J. Mar. Freshw. Res., 38, 671–683.

Church, J., and F. Boland (1983): A permanent undercurrent adjacent to the

great barrier reef. J. Phys. Oceanogr., 13(9), 1747–1749.

Cibot, C., E. Maisonnave, L. Terray, and B. Dewitte (2005): Mechanisms of tropical Pacific interannual-to-decadal variability in the ARPEGE/ORCA global

coupled model. Climate Dyn., 24(7–8), 823–842, 10.1007/s00382-004-

0513-y.

Davis, R.E., W.S. Kessler, R. Lukas, R.A. Weller, D.W. Behringer, D.R. Cayan, D.B.

Chelton, C. Eriksen, S. Esbensen, R.A. Fine, I. Fukumori, M.C. Gregg, E.

Harrison, G.C. Johnson, T. Lee, N.J. Mantua, J.P. McCreary, M.J. McPhaden,

J.C. McWilliams, A.J. Miller, H. Mitsudera, P.P. Niiler, B. Qiu, D. Raymond, D.

Roemmich, D.L. Rudnick, N. Schneider, P.S. Schopf, D. Stammer, L. Thompson, and W.B. White (2000): Implementing the Pacific Basin Extended Climate Study (PBECS). U.S. CLIVAR Office Report, Version 2000.2, U.S. CLIVAR Office, 123 pp.

Delcroix, T. (1998): Observed surface oceanic and atmospheric variability in the

tropical Pacific at seasonal and ENSO timescales: A tentative overview. J.

Geophys. Res., 103(C9), 18,611–18,633.

Delcroix, T., S. Cravatte, and M. McPhaden (2007): Decadal variations and

trends in tropical Pacific sea surface salinity since 1970. J. Geophys. Res.,

112, C03012, doi: 10.1029/2006JC003801.

Delcroix, T., and C. Hénin 1989: Mechanisms of subsurface thermal structure

and sea surface thermohaline variabilities in the southwestern tropical Pacific during 1975–85. J. Mar. Res., 47, 777–812.

Donguy, J.-R. (1994): Surface and subsurface salinity in the tropical Pacific

Ocean: Relations with climate. Prog. Oceanogr., 34, 45–78.

Donguy, J.-R., and G. Meyers (1996): Mean annual variation of transport of major currents in the tropical Pacific Ocean. Deep-Sea Res. I, 43, 1105–1122.

Emanuel, K. (2005): Increasing destructiveness of tropical cyclones over the

past 30 years. Nature, 436(7051), 686–688.
28 Ganachaud et al.—SPICE, Part I. Scientific Background

Fedorov, A.V., and S.G. Philander (2001): A stability analysis of Tropical OceanAtmosphere Interactions: Bridging measurements and theory for El Niño.

J. Climate., 14(14), 3086–3101.

Folland, C.K., J.A. Renwick, M.J. Salinger, and A.B. Mullan (2002): Relative influences of the Interdecadal Pacific Oscillation and ENSO on the south Pacific Convergence Zone. Geophys. Res. Lett., 29(13), 1643, doi: 10.1029/

2001GL014201.

Fukumori, I., T. Lee, B. Cheng, and D. Menemenlis (2004): The origin, pathway and destination of the Niño-3 water estimated by a simulated passive

tracer and its adjoint. J. Phys. Oceanogr. 34(3), 582–604.

Garreaud, R.D., and D.S. Battisti (1999): Interannual (ENSO) and Interdecadal

(ENSO-like) variability in the southern hemisphere tropospheric circulation, J. Climate, 12(7), 2113–2123.

Gibbs, M.T., J.H. Middleton, and P. Marchesiello (1998): Baroclinic response of

Sydney shelf waters to local wind and deep ocean forcing. J. Phys. Oceanogr.,

28(2), 178–190.

Giese, B., C. Urizar, and N. Fuˇckar (2002): Southern hemisphere origins of the

1976 climate shift. Geophys. Res. Lett., 29(2), 1014, doi: 10.1029/

2001GL013268.

Godfrey, J.S. (1989): A Sverdrup model of the depth-integrated flow for the

world ocean allowing for island circulations. Geophys. Astrophys. Fluid

Dyn., 45, 89–112.

Gouriou, Y., and T. Delcroix (2002): Seasonal and ENSO variations of sea surface salinity and temperature in the South Pacific Convergence Zone during 1976–2000. J. Geophys. Res., 107(C12), 3185, doi: 10.1029/2001JC000830.

Gouriou, Y., and J. Toole (1993): Mean circulation of the upper layers of the

western equatorial Pacific Ocean. J. Geophys. Res., 98(C12), 22,495–22,520.

Griffiths, G., M. Salinger, and I. Leleu (2003): Trends in extreme daily rainfall

across the South Pacific and relationship to the South Pacific Convergence

Zone. Int. J. Climatol., 23(8), 847–869.

Gu, D., and S.G.H. Philander (1997): Interdecadal climate fluctuations that depend on exchanges between the tropics and extratropics. Science, 275(5301),

805–807.

Hanawa, K., and L. Talley (2001): Mode waters. In Ocean Circulation and ClimateObserving and Modelling the Global Ocean, G. Siedler, J. Church, and J.

Gould (eds.), Academic Press, 373–368.

Hirst, A., and S. Godfrey (1993): The role of Indonesian Throughflow in a global

ocean GCM. J. Phys. Oceanogr., 23(6), 1057–1086.

Holbrook, N.J., and N.L. Bindoff (1997): Interannual and decadal temperature

variability in the southwest Pacific Ocean between 1955 and 1988. J. Climate, 10(5), 1035–1049.

Holbrook, N.J., and N.L. Bindoff (1999): Seasonal temperature variability in the

upper southwest Pacific Ocean. J. Phys. Oceanogr., 29(3), 366–381.

Holbrook, N.J., and N.L. Bindoff (2000a): A statistically efficient mapping technique for four-dimensional ocean temperature data. J. Atmos. Ocean. Technol., 17(6), 831–846.

Holbrook, N.J., and N.L. Bindoff (2000b): A digital upper ocean temperature

atlas for the southwest Pacific: 1955–1988. Aust. Meteorol. Mag., 49, 37–49.
Section 7. References 29

Holbrook, N.J., P.S.-L. Chan, and S.A. Venegas (2005): Oscillatory and propagating modes of temperature variability at the 3–3.5- and 4–4.5-yr time scales

in the upper southwest Pacific Ocean. J. Climate, 18(5), 719–736.

Holbrook, N.J., and A.M. Maharaj (2007): Southwest Pacific Subtropical Mode

Water: a climatology. Prog. Oceanogr. (accepted).

Holland, G.J., A.H. Lynch, and L.M. Leslie (1987): Australian east-coast cyclones.

Part I: Synoptic overview and case study. Mon. Wea. Rev., 115(12), 3024–

3036.

Hopkins, L.C., and G.J. Holland (1997): Australian heavy-rain days and associated east coast cyclones: 1958–92. J. Climate, 10(4), 621–635.

Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K.

Maskell, and C.A. Johnson (2001): Climate Change 2001: The Scientific Basis. Cambridge University Press, 882 pp., ISBN 0521014956.

Hurell, J., and D. Vincent (1987): Significance of the South Pacific Convergence

Zone (SPCZ) in the energy budget of the southern hemisphere tropics. Mon.

Wea. Rev., 115(8), 1797–1801.

Huyer, A., R.L. Smith, P.J. Stabeno, J.A. Church, and N.J. White (1988): Currents

off southeastern Australia: Results from the Australian Coastal Experiment.

Aust. J. Mar. Freshw. Res., 39, 245–288.

Inoue, M., and S. Welsh (1993): Modeling seasonal variability in the wind-driven

upper-layer circulation in the Indo-Pacific region. J. Phys. Oceanogr., 23(7),

1411–1436.

Izumo, T., J. Picaut, and B. Blanke (2002): Tropical pathways, equatorial undercurrent variability and the 1998 La Niña. Geophys. Res. Lett., 29(22), 2080,

doi: 10.1029/2002GL015073.

Johnson, G.C. (2006): Generation and initial evolution of a mode water θ-S

anomaly. J. Phys. Oceanogr., 36(4), 739–751.

Johnson, G., and M. McPhaden (1999): Interior pycnocline flow from the subtropical to the equatorial Pacific Ocean. J. Phys. Oceanogr., 29(12), 3073–

3089.

Kelly, K. (2004): The relationship between oceanic heat transport and surface

fluxes in the western North Pacific: 1970–2000. J. Climate, 17(3), 573–588.

Kessler, W.S., R.E. Davis, K. Takeuchi, and R. Lukas (2001): The Pacific Basin

Extended Climate Study. In: Observing the Ocean in the 21st Century, C.J.

Koblinsky, and N.R. Smith (eds.), Bureau of Meteorology, Melbourne, Australia.

Kessler, W., and L. Gourdeau (2006): Wind-driven zonal jets in the South Pacific

Ocean. Geophys. Res. Lett., 33, L03608, doi: 10.1029/2005GL025084.

Kessler, W., and L. Gourdeau (2007): The annual cycle of circulation of the

southwest subtropical Pacific analyzed in and ocean GCM. J. Phys.

Oceanogr., in press.

Kiladis, G.N., H. von Storch, and H. van Loon (1989): Origin of the South Pacific

convergence zone. J. Climate, 2(10), 1185–1195.

Kleeman, R., J.P. McCreary, Jr., and B.A. Klinger (1999): A mechanism for the

decadal variation of ENSO. Geophys. Res. Lett., 26(12), 1743–1746.

Lee, T., and I. Fukumori (2003): Interannual to decadal variations of tropicalsubtropical exchanges in the Pacific Ocean: Boundary versus interior transports. J. Climate, 16(24), 4022–4042.
30 Ganachaud et al.—SPICE, Part I. Scientific Background

Li, J., X. Zhang, Y. Yu, and F. Dai (2004): Primary reasoning behind the double ITCZ phenomenon in a coupled ocean-atmosphere general circulation

model. Advances Atmos. Sci., 21, 857–867.

Lindstrom, E., R. Lukas, R. Fine, E. Firing, J.S. Godfrey, G. Meyers, and M.

Tsuchiya (1987): The Western Equatorial Pacific Ocean Circulation Study.

Nature, 330(6148), 533–537.

Lindstrom, E., J. Butt, R. Lukas, and S. Godfrey (1990): The flow through Vitiaz Strait and St. Georges Channel, Papua New Guinea. In The Physical

Oceanography of Sea Straits, L. Pratt (ed.), Kluwer Academic, Dordrecht,

171–189.

Liu, Z., L. Wu, and E. Bayler (1999): Rossby wave-coastal Kelvin wave interaction in the extratropics. Part I: Low-frequency adjustment in a closed basin.

J. Phys. Oceanogr., 29(9), 2382–2404.

Lukas, R., R.E. Davis, and W.S. Kessler (1998): Prospectus for a Pacific Basinwide

Extended Climate Study. Texas A&M University.

Luo, J.-J., S. Masson, S.K. Behera, P. Delecluse, S. Gualdi, A. Navarra, and T. Yamagata (2003): South Pacific origin of the decadal ENSO-like variation as

simulated by a coupled GCM. Geophys. Res. Lett., 30(24), 2250, doi: 10.1029/

2003GL018649.

Luo, Y., L. Rothstein, R.-H. Zhang, and A. Bussalacchi (2005): On the connection

between South Pacific subtropical spiciness anomalies and decadal equatorial variability in an ocean general circulation model. J. Geophys. Res.,

110, C10002, doi: 10.1029/2004JC002655.

Luo, J.-J., and T. Yamagata (2001): Long-term El Niño-Southern Oscillation

(ENSO)-like variation with special emphasis on the South Pacific. J. Geophys. Res., 106(C10), 22,211–22,227.

Lyman, J., J. Willis, and G. Johnson (2006): Recent cooling of the upper ocean.

Geophys. Res. Lett., 33, L18604, doi: 10.1029/2006GL027033.

Lysne, J., P. Chang, and B. Giese (1997): Impact of extratropical Pacific on equatorial variability. Geophys. Res. Lett., 24(21), 2589–2592.

McCarty, J.J., O.F. Canziani, N.A. Leary, D.J. Dokken, and K.S. White (2001): Climate Change 2001: Impacts, Adaptation, and Vulnerability. Cambridge

University Press, 1032 pp., ISBN 0521807689.

McCreary, J., and P. Lu (1994): Interaction between the subtropical and equatorial ocean circulations: The subtropical cell. J. Phys. Oceanogr., 24(2), 466–

497.

McDonnell, K.A., and N.J. Holbrook (2004a): A Poisson regression model of

tropical cyclogenesis for the Australian-southwest Pacific Ocean region.

Wea. Forecast., 19(2), 440–455.

McDonnell, K.A., and N.J. Holbrook (2004b): A Poisson regression model approach to predicting tropical cyclogenesis in the Australian/southwest Pacific Ocean region using the SOI and saturated equivalent potential temperature gradient as predictors. Geophys. Res. Lett., 31, L20110, doi:

10.1029/2004GL020843.

McGregor, S., N.J. Holbrook, and S.B. Power (2004): On the dynamics of interdecadal thermocline depth and sea surface temperature variability in

the low to mid-latitude Pacific Ocean. Geophys. Res. Lett., 31, L24201, doi:

10.1029/2004GL021241.
Section 7. References 31

McGregor, S., N.J. Holbrook, and S.B. Power (2007): Interdecadal sea surface

temperature variability in the tropical Pacific Ocean. Part I: The role of offequatorial wind stresses and oceanic Rossby waves. J. Climate (in press).

McPhaden, M., and D. Zhang (2002): Slowdown in the meridional overturning

circulation in the upper Pacific Ocean. Nature, 415(6872), 603–608.

McPhaden, M., and D. Zhang (2004): Pacific Ocean circulation rebounds. Geophys. Res. Lett., 31, L18301, doi: 10.1029/2004GL020727.

Maharaj, A.M., P. Cipollini, and N.J. Holbrook (2005): Observed variability of the

South Pacific westward sea level anomaly signal in the presence of bottom

topography. Geophys. Res. Lett., 32, L04611, doi: 10.1029/2004GL020966.

Maharaj, A.M., P. Cipollini, N.J. Holbrook, P.D. Killworth, and J.R. Blundell (2007):

An evaluation of the classical and extended Rossby wave theories in explaining spectral estimates of the first few baroclinic modes in the South

Pacific Ocean. Ocean Dyn., online first, doi: 10.1007/s10236-006-0099-5.

Martinez, E., and K. Maamaatuaiahutapu (2004): Island mass effect in the Marquesas Islands: Time variations. Geophys. Res. Lett., 31, L18307, doi:

10.1029/2004GL020682.

Mata, M.M., M. Tomczak, S. Wijffels, and J.A. Church (2000): East Australian

Current volume transports at 30◦S: Estimates from the World Ocean Circulation Experiment hydrographic sections PR11/P6 and the PCM3 current

meter array. J. Geophys. Res., 105(C12), 28509, 28,509–28,526.

Moon, B.-K., S.W. Yeh, B. Dewitte, J.-G. Jhun, and I.S. Kang (2007): Source of low

frequency modulation of ENSO amplitude in a CGCM, in press

(swyeh@kordi.re.kr).

Nakano, H., and H. Hasumi (2005): A series of zonal jets embedded in the broad

zonal flows in the Pacific obtained in eddy-permitting ocean general circulation models. J. Phys. Oceanogr., 35(4), 474–488.

Nonaka, M., S.-P. Xie, and J.P. McCreary (2002): Decadal variations in the subtropical cells and equatorial Pacific SST. Geophys. Res. Lett., 29(7), 1116, doi:

10.1029/2001GL013717.

Oke, P.R., and J.H. Middleton (2001): Nutrient enrichment off Port Stephens:

The role of the East Australian Current. Cont. Shelf Res., 21(6–7), 587–606.

Overpeck, J.T., B.L. Otto-Bliesner, G.H. Miller, D.R. Muhs, R.B. Alley, and J.T.

Kiehl (2006): Paleoclimatic evidence for future ice-sheet instability and

rapid sea-level rise. Science, 311(5768), 1747–1750.

Pelling, M., and J. Uitto (2001): Small island developing states: Natural disaster

vulnerability and global change. Environ. Haz., 3, 49–62.

Pierce, D., T. Barnet, and M. Latif (2000): Connections between the Pacific

Ocean tropics and midlatitudes on decadal timescales. J. Climate, 13(6),

1173–1194.

Pittock, B., D. Wratt, R. Basher, B. Bates, M. Finlayson, H. Gitay, and A. Woodward (2001): Australia and New Zealand. Climate Change 2001: Impacts,

Adaptation and Vulnerability. J.J. McCarthy et al. (eds.), Cambridge University Press, 591–639.

Power, S., T. Casey, S. Folland, A. Colman, and V. Mehta (1999): Inter-decadal

modulation of the impact of ENSO on Australia. Climate Dyn., 15, 319–324.
32 Ganachaud et al.—SPICE, Part I. Scientific Background

Qiu, B., and T.S. Durland (2002): Interaction between an island and the ventilated thermocline: Implication for the Hawaiian Lee Countercurrent. J.

Phys. Oceanogr., 32(12), 3408–3426.

Qiu, B., and S. Chen (2004): Seasonal modulations in the eddy field of the South

Pacific Ocean. J. Phys. Oceanogr., 34(7), 1515–1527.

Qiu, B., and S. Chen (2006): Decadal variability in the large-scale sea surface

height field of the South Pacific Ocean: Observations and causes. J. Phys.

Oceanogr., 36(9), 1751–1762.

Qu, T., and E. Lindstrom (2002): A climatological interpretation of the circulation in the western south Pacific. J. Phys. Oceanogr., 32(9), 2492–2508.

Reid, J. (1997): On the total geostrophic circulation of the Pacific Ocean: Flow

patterns, tracers, and transports. Prog. Oceanogr., 39(4), 263–352.

Ridgway, K.R. (2006): East Australian Current eddies: A response to remotely

forced Rossby waves and local topography. Submitted to Deep-Sea Res.

Ridgway, K., and J. Dunn (2003): Mesoscale structure of the East Australian Current System and its relationship with topography. Prog. Oceanogr., 56(2),

189–222.

Ridgway, K.R., J.S. Godfrey (1997): Seasonal cycle of the East Australian Current.

J. Geophys. Res, 102(C10), 22,921–22,936.

Ridgway, K.R., J.S. Godfrey, G. Meyers, and R. Bailey (1993): Sea level response

to the 1986–1987 El Niño-Southern event in the western Pacific in the vicinity of Papua New Guinea. J. Geophys. Res., 98(9), 16,387–16,395.

Rochford D.J. (1975): Nutrient enrichment of Australian coastal waters. II: Laurieton upwelling. Aust. J. Mar. Freshw. Res., 26, 233–243.

Roemmich, D., J. Gilson, J. Willis, P. Sutton, and K. Ridgway (2005): Closing

the time-varying mass and heat budgets for large ocean areas: The Tasman

Box. J. Climate, 18(13), 2330–2343.

Roemmich, D., J. Gilson, R. Davis, P. Sutton, S. Wijffels, and S. Riser (2007): Decadal spinup of the South Pacific subtropical gyre. J. Phys. Oceanogr., 37(2),

162–173.

Salinger, J., J. Renwick, and A. Mullan (2001): Interdecadal Pacific Oscillation

and South Pacific climate. Int. J. Climatol., 21(14), 1705–1721.

Schneider, N., 2004. The response of tropical climate to the equatorial emergence of spiciness anomalies. J. Climate, 17(5), 1083–1095.

Sharples, J. (1997): Cross-shelf intrusion of subtropical water into the coastal

zone of northeast New Zealand. Cont. Shelf. Res., 17(7), 835–857.

Sharples, J., and M.J.N. Greig (1998): Tidal currents, mean flows, and upwelling

on the north-east shelf of New Zealand. N. Z. J. Mar. Freshw. Res., 32, 215–

231.

Sokolov, S., and S. Rintoul (2000): Circulation and water masses of the southwest Pacific: WOCE section P11, Papua New Guinea to Tasmania. J. Mar.

Res., 58(2), 223–268.

Speich S., B. Blanke, P. de Vries, S. Drijfhout, K. Döös, A. Ganachaud, and R.

Marsh (2002): Tasman leakage: A new route in the global ocean conveyor

belt. Geophys. Res. Lett., 29(10), 1416, doi: 10.1029/2001GL014586.

Sprintall, J., D. Roemmich, B. Stanton, and R. Bailey (1995): Regional climate

variability and ocean heat transport in the Southwest Pacific Ocean. J. Geophys. Res., 100(C8), 15,865–15,871.
Section 7. References 33

Stanton, B., and P. Sutton (2003): Velocity measurements in the East Auckland

Current north-east of North Cape, New Zealand. N. Z. J. Mar. Freshw. Res.,

37, 195–204.

Stanton, B., D. Roemmich, and M. Kosro (2001): A shallow zonal jet south of

Fiji. J. Phys. Oceanogr., 31(10), 3127–3130.

Sutton, P. (2001): Detailed structure of the Subtropical Front over the Chatham

Rise, east of New Zealand. J. Geophys. Res., 106(C12), 31,045–31,056.

Sutton, P., M. Bowen, and D. Roemmich (2005): Decadal temperature changes

in the Tasman Sea. N. Z. J. Mar. Freshw. Res., 39, 1321–1329.

Sutton, P., and D. Roemmich (2001): Ocean temperature climate off north-east

New Zealand. N. Z. J. Mar. Freshw. Res., 35, 553–565.

Taft, B.A., and W.S. Kessler (1991): Variations of zonal currents in the central

tropical Pacific during 1970 to 1987: Sea level and dynamic height measurements. J. Geophys. Res., 96(C7), 12,599–12,618.

Talley, L., and J. Sprintall (2005): Deep expression of the Indonesian Throughflow: Indonesian intermediate water in the South Equatorial Current. J.

Geophys. Res., 110, C10009, doi: 10.1029/2004JC002826.

Tilburg, C.E., H.E. Hurlburt, J.J. O’Brien, and J.F. Shriver (2001): The dynamics

of the East Australian Current system: The Tasman Front, the East Auckland Current, and the East Cape Current. J. Phys. Oceanogr., 31(10), 2917–

2943.

Tilburg, C.E., H.E. Hurlburt, J.J. O’Brien, and J.F. Shriver (2002): Remote topographic forcing of a baroclinic western boundary current: An explanation

for the Southland Current and the pathway of the Subtropical Front east of

New Zealand. J. Phys. Oceanogr., 32(11), 3216–3232.

Timmermann, A. (2003): Decadal ENSO amplitude modulations: A nonlinear

paradigm. Global Planet. Change, 770, 1–22.

Tsuchiya, M. (1981): The origin of the Pacific Equatorial 13◦C water. J. Phys.

Oceanogr., 11(6), 794–812.

Tsuchiya, M., R. Lukas, R.A. Fine, E. Firing, and E. Lindstrom (1989): Source

waters of the Pacific Equatorial Undercurrent. Prog. Oceanogr., 23(2), 101–

147.

Vincent, D. (1995): The South Pacific Convergence Zone (SPCZ): A review. Mon.

Wea. Rev., 122(9), 1949–1970.

Wang, X., F.F. Jin, and Y. Wang (2003b): A tropical ocean recharge mechanism

for climate variability. Part II: A unified theory for decadal and ENSO modes.

J. Climate, 16(22), 3599–3616.

Wang, X.L., and C.F. Ropelewski (1995): An assessment of ENSO-scale secular

variability. J. Climate, 8(6), 1584–1599.

Webb, D. (2000): Evidence for shallow zonal jets in the South Equatorial Current

region of the southwest Pacific. J. Phys. Oceanogr., 30(4), 706–720.

Webster, P., G. Holland, J. Curry, and H. Chang (2005): Changes in tropical cyclone number, duration, and intensity in a warming environment. Science,

309(5742), 1844–1846.

Willis, J., D. Roemmich, and B. Cornuelle (2004): Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global

scales. J. Geophys. Res., 109, C12036, doi: 10.1029/2003JC002260.
34 Ganachaud et al.—SPICE, Part I. Scientific Background

Wolanski, E., P. Colin, J. Naithani, E. Deleersnijder, and Y. Golbuu (2004): Large

amplitude, leaky, island-generated, internal waves around Palau, Micronesia. Estuar. Coast. Shelf Sci., 60(4), 705–716.

Wood, R., and the VOCALS Scientific Working Group (2006): VOCALS—Regional

Experiment: Scientific Programme overview, www.eol.ucar.edu/

projects/vocals.

Yeager, S.G., and W.G. Large (2004): Late-winter generation of spiciness on subducted isopycnals. J. Phys. Oceanogr., 34(7), 1528–1547.

Yoshikane, T., and F. Kimura (2003): Formation and mechanism of the simulated SPCZ and Baiu front using a regional climate model. J. Atmos. Sci.,

60(21), 2612–2632.

Yu, B., and G.J. Boer (2004): The role of the western Pacific in decadal variability. Geophys. Res. Lett., 31, L02204, doi: 10.1029/2003GL018471.

Zhang, C. (2001): Double ITCZs. J. Geophys. Res., 106(D11), 11,787–11,792.

Zhang, R.H., L.M. Rothstein, and A.J. Busalacchi (1998): Origin of upper-ocean

warming and El Niño change on decadal scales in the tropical Pacific Ocean.

Nature, 391(6670), 879–883.
Section 8. Glossary of Acronyms 35

8. Glossary of Acronyms

AAIW Antarctic Intermediate Water

ACC Antarctic Circumpolar Current

ADCP Acoustic Doppler Current Profiler

AIMS Australian Institute of Marine Science

ANR Agence Nationale de la Recherche (Funding agency, France)

CARS CSIRO Atlas of Regional Seas

CLIVAR Climate Variability and Predictability

CMAR CSIRO Marine and Atmospheric Research

COADS Comprehensive Ocean-Atmosphere Data Set

CSIRO Commonwealth Scientific and Industrial Research

Organization

EAC East Australia Current

EAUC East Auckland Current

ECC East Cape Current

ENSO El Niño-Southern Oscillation

ERS1/2 European Remote-Sensing Satellites1/2

ERSST Extended Reconstructed Sea Surface Temperature

EUC Equatorial Undercurrent

GBRUC Great Barrier Reef Undercurrent

IMET Improved Meteorology system for marine meteorological

observations

INSTANT International Nusantara Stratification and Transport

IPCC Intergovernmental Panel on Climate Change

IPRC International Pacific Research Center

IRD Institut de Recherche pour le Développement

ITCZ Intertropical Convergence Zone

LEFE Les Enveloppes Fluides de l’Environement (Funding agency,

France)

LEGOS Laboratoire d’Etudes en Géophysique et Océanographie

Spatiales

MOMA Modular Ocean Model—Array processor version

NCJ North Caledonian Jet

NGCC New Guinea Coastal Current

NGCUC New Guinea Coastal Under Current

NIWA National Institute of Water and Atmospheric Research

NQC North Queensland Current

NOAA National Oceanic and Atmospheric Administration
36 Ganachaud et al.—SPICE, Part I. Scientific Background

NTIS National Technical Information Service

NVJ North Vanuatu Jet

OAR Oceanic and Atmospheric Research [NOAA]

PACSWIN PACific Source Water Investigation

PBECS Pacific Basin Extended Climate Study

PI-GOOS Pacific Islands Global Ocean Observing System

PINs Pacific Island Nations

PMEL Pacific Marine Environmental Laboratory [NOAA]

PRIDE Pacific Region Integrated Data Enterprise

PSU practical salinity units

REMO Max-Planck Institut für Meteorologie Regional climate Model

RiCom River, Coast and ocean model

ROMS Regional Ocean Modeling System

RV Research Vessel

SAM South Annular Mode

SAMW SubAntarctic Mode Water

SCJ South Caledonian Jet

SEC South Equatorial Current

SECC South Equatorial Countercurrent

SIO Scripps Institution of Oceanography

SLW Subtropical Lower Water

SOEST School of Ocean and Earth Science and Technology

SOPAC South Pacific Applied Geoscience Commission

SPCZ South Pacific Convergence Zone

SPESMW South Pacific Eastern Subtropical Mode Water

SPICE Southwest Pacific Ocean Circulation and Climate Experiment

SPMW South Pacific Mode Water

SPREP Pacific Regional Environment Programme

SSH Sea Surface Height

SST Sea Surface Temperature

START Global Change System for Analysis, Research, and Training

STCC Subtropical Countercurrent

STF Subtropical Front

STMW Subtropical Mode Water

SVJ South Vanuatu Jet

T/P TOPEX/Poseidon

TAO Tropical Atmosphere Ocean

TF Tasman Front

TO Tasman Outflow

UNESCO United Nations Educational, Scientific and Cultural

Organization

USP University of South Pacific

VOS Voluntary Observing Ship
Section 8. Glossary of Acronyms 37

WBC Western Boundary Current

WE Wairarapa Eddy

WEPOCS Western Equatorial Pacific Ocean Circulation Study

WOCE World Ocean Circulation Experiment

XBT eXpandable Bathy Thermograph

ZONECO Zone Economique Exclusive de Nouvelle Calédonie (Applied

oceanic and shore research, New Caledonia)