Oceans Program

The Southern Ocean and Sea-Level Rise
1. Overview of the program + who’s involved
2. Plans for contributing to IPCC 5 th Assessment

Evolving state of the Southern Ocean
1. How is the Southern Ocean changing?
2. What is the impact of changes in ocean
circulation and water properties on the
cryosphere, biogeochemical cycles and biology
of the Southern Ocean?
3. What is the cause of observed changes in
the Southern Ocean? How much of the signal is
consistent with anthropogenic climate change?

Research plan: Fieldwork
Argo, including ice floats
Moorings: Mertz polynya region and Antarctic
margin near Casey
Repeat hydrographic + tracer sections
• Dec 2010: southern end of SR3 + shelf/slope
• Feb 2012: recover 115E moorings
• Jan 2013: Mertz area, on Tangaroa
• I9S (115E): 2011-12? Or 2014?

Modelling and synthesis
Analyse output from heirarchy of models, from
regional high-resolution to global coarseresolution
climate models.
Detection – attribution studies.

Who’s involved?
ACE + local partners:
•Steve Rintoul
•Nathan Bindoff
•Serguei Sokolov
•Mark Rosenberg
•2 new hires (physical oceanographers)
•Students
International:
•Eberhard Fahrbach (AWI, Germany)
•Shigeru Aoki (ILTS, Japan)
•Rosemary Morrow (LEGOS, France)
•Mike Williams (NIWA, NZ)
•Weidong Yu (FIO, China)

ACE Science for IPCC 5 th Assessment (AR5)
Strategy:
• Nominate for lead author positions
• Focus our effort on high impact science relevant to AR5

IPCC Oceans chapter outline
Chapter 3: Observations: Ocean
• Changes in ocean temperature and heat content
• Ocean salinity change and freshwater fluxes
• Sea level change, ocean waves and storm surges
• Ocean biogeochemical changes, including ocean
acidification
• Changes in ocean surface processes
• Changes in ocean circulation
• Spatial and temporal patterns of ocean variability

Future of the overturning circulation
Rintoul, 2001

Overturning circulation acts as a valve regulating
exchange between atmosphere and deep sea
Sigman et al.,
Nature, 2010

Water mass changes:
freshening of Antarctic Bottom Water
neutral density
salinity

Warming of the abyssal ocean
Purkey and Johnson, 2010

Warming of deep North Pacific caused by
change in air-sea flux in East Antarctica?
Masuda et al., Science, 2010

Kerguelen Deep Western Boundary Current
Experiment: Australia - Japan
12 Sv ± 1.2 Sv of AABW ( 20 cm s -1 .
Fukamachi et al.,
Nature Geoscience,
2010

Ekman, eddies and mean flow all contribute to
transfer of water between the surface and interior
Sallée et al 2009

Subduction hot-spots

Subduction hot-spots and distribution of potential
vorticity and anthropogenic CO 2
PV on γ = 26.8
C anthrop on γ = 26.8
Red: subduction
Color: PV (yellow is low)
Sallee, Speer, Rintoul + Wijffels, JPO, 2009
green: subduction
yellow: upwelling
Color: C_ant (red is high)

Sallee, Speer, Rintoul, Nature Geoscience, 2010
Structure and variability of the mixed layer
Seasonal
variations in
mixed layer
depth
Variations in
mixed layer
depth with the
Southern
Annular Mode
SAM + SAM -

Response of upper limb of overturning to climate
change
Downes, Bindoff & Rintoul, 2010

Can IPCC models parameterise the effect of
eddies?
Sallée & Rintoul, in prep

Yes, if you use the right coefficient (which no
one does)

Trends in sea surface height: 1992-2007
Sokolov and Rintoul, JGR-Oceans 2009a,b

Southward shift of ACC fronts
Change in latitude of fronts (degrees)
Sokolov and Rintoul, JGR, 2009
year

Diagnosing the causes of SO change
Air-sea flux
Southward
shift of fronts
Sum
Sum from a
different
analysis
Meijers et al., sub.

Loss of Antarctic ice: melt by a warmer ocean?
Antarctic mass
loss increased by
70% in last
decade, as a result
of warmer air and
sea temperatures.
Rignot et al., Nature
Geoscience, 2008

East Antarctica more vulnerable than expected?
Fox, Science, 2010

Quantifying basal melt potential with elephant
seal data
Cross-shelf intrusions of warm
MCDW observed near Budd
Glacier (109E) and Dibble Ice
Tongue (135E).
Bestley, Rintoul and Charassin, in prep

Basal melt rates vs. temperature elevation above
freezing point temperature at grounding line
Bestley, Rintoul and Charassin, in prep

Massom et al., 2001

With additional
support from
The Southern Ocean
Observing System
(SOOS)
www.scar.org/soos

Summary
Oceans program making good progress.
Strategy for IPCC in place:
• Lead authors
• Target effort at key uncertainties:
• Overturning circulation (upper and lower limb)
• Ocean change (shallow and deep)
• Ocean – ice interaction
• Modes of variability
• Detection and attribution
• Model improvements
• Marine impacts

Mawson meets Scott
The Monthly, July 2010

Andrew Meijers

EAST-WEST 5
Andrew Meijers + Ben Galton-Fenzi

B09B
C28
MGT
15-03-2010 (TerraSAR-X)

Measuring the ACC flow through gaps in the
Macquarie Ridge

Measuring the ACC flow through gaps in the
Macquarie Ridge
Strong barotropic
flow in the branch of
the Subantarctic
Front passing
through the 50 km
wide gap north of
Macquarie Island.
Mean transport of
57.0 ± 8.5 Sv.

Injection of Subantarctic Mode Water
Herraiz-Borreguero + Rintoul, subm