12th GCOS-GOOS-WCRP Ocean Observations Panel for Climate - Paris, May 2007

Emerging Southern Ocean Science and Observing System Issues

Kevin Speer, Mike Sparrow

with input from various groups and individuals…

Southern Ocean Panel1. To design a strategy to assess climate variability and predictability of the

coupled ocean-atmosphere-ice system in the Southern Ocean region.

2. To oversee and coordinate Southern Ocean process studies, sustained observations, and model experiments needed to meet the objectives of CLIVAR, CliC and SCAR.

http://www.clivar.org/organization/southern/southern.php

Lumpkin and Speer (2006)

• The International Polar year

e.g. science and coordination issues, IPY period synthesis…

• The observing system in the Southern Ocean region

e.g. new technology and opportunities, the SOOS, gaps…

• Indices for the Southern Ocean region

Overview

Climate research themes for the IPY in the SO

• Antarctica and the Southern Ocean in the global water cycle

• Southern hemisphere teleconnections• Climate processes at the Antarctic continental

margin • Climate – ecosystem – biogeochemistry

interactions in the Southern Ocean• Records of past Antarctic climate variability and

change

• Synoptic multi-disciplinary transects

• Sea ice thickness

• Ocean circulation under sea ice

• Southern Ocean Argo… (IPY enhancement?)

• Ice cores

• Ice cavity observations

SO IPY enhancements to sustained observing system:

Two main “umbrella” projects for (physical) oceanography in the SO region:

• CASO (Climate of Antarctica and the Southern Ocean), coordinated by the SO CLIVAR/CliC/SCAR panel

• SASSI (Synoptic Antarctic Shelf-Slope Interactions Study), coordinated by iAnZone

(+ cross relationships to others such as ICED-IPY)

IPY: SO Science and Coordination Issues

CASO

http://www.clivar.org/organization/southern/CASO/index.htm

CASO aims to:

• Obtain the first circumpolar snapshot of the Southern Ocean, including physical, ecological and biogeochemical properties

• Measure the circumpolar extent and thickness of Antarctic sea ice through an annual cycle for the first time

• Observe the sub-ice ocean circulation, water mass properties and biological distributions

CASO

http://www.clivar.org/organization/southern/CASO/index.htm

Reality:

• Business as usual + But…the + is significant: substantial increase in data for the period 2007-2009 in terms of Southern Ocean hydrography

CASO ‘gaps’:

• Integrated modelling (but SO panel drafting white paper)• Open ocean Argo? For now, probably looks better than we dared to hope. Need to continue seeding to ensure coverage during 2007-9.• Argo under ice: good, growing coverage in Weddell but nothing elsewhere• Zonal lines/moorings in subtropical Indian+Pacific• Missing southern boundaries: some sections not done on ice breakers• Little increase in commitment to IPAB

CASO

http://www.clivar.org/organization/southern/CASO/index.htm

SASSI

http://woceatlas.tamu.edu/sassi/

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SASSI

http://woceatlas.tamu.edu/sassi/

• Theme 1: SASSI will provide a unique synoptic snapshot of the Antarctic continental shelf and slope environment, including physical (iAnZone), biogeochemical (GEOTRACES, SOLAS, IMBER) and biodiversity (CoML, GLOBEC) measurements: a legacy against which to measure future change.

• Theme 2: SASSI aims to understand and parameterise the continental shelf/slope processes that are currently absent from climate models, yet are critical to understanding global climate variability.

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Global IPY-period synthesis

• The International Polar Year will provide a data-intensive period during 2008-2009.

• Regional analyses are planned but a synthesis of global scope is needed to address heat and freshwater transports at the largest scales.

• Build support for a focused effort to produce a global ocean synthesis that incorporates IPY period data (GSOP, iAnZone, SO panel, SO Expert group…).

• Will need support of IPY related groups such as SCAR to create data archives and access. These efforts are starting now.

The Observing System in the SO Region

http://www.clivar.org/organization/southern/CLIVAR_CliC_Obs.html

The Observing System in the SO Region

http://www.clivar.org/organization/southern/SCAR_SCOR/index.htmhttp://www.clivar.org/organization/southern/CLIVAR_CliC_Obs.html

The Observing System in the SO Region: Argo

http://argo.ocean.fsu.edu/

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• Argo under ice (e.g. AWI group in Weddell)

• Use of animal-borne sensors (SEaOS, MEOPS etc.)

• Sea-ice buoys

• Ice cavity monitoring stations

The Observing System in the Southern Ocean Region: New Technology and Opportunities

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Ice compatibility of ARGO floats: a 3 step process

Ice sensing algorithm (ISA)

Interim storage

(iStore)

RAFOS

Checks temperature in the upper 50 m, ascent aborted if

near freezing point

Provides delayed mode profile when surfacing

impossible

Provides subsurface profile position when surfacing impossible

Tested successfully

about 80% survival rate

additional modifications are planned

8 NEMO floats are

currently under test and delivered first results

Tested in 2003/4 with 5 RAFOS floats: tracking range is at least 600 km

throughout season.

Now standard for all AWI float orders (APEX and NEMO)

Ordered for all further NEMO floats

Ordered for further NEMO floats

(APEX and NEMO)

ISA/iSore/RAFOS – Float = fully ice compatible

Sound sources (red: deployed by Keith Nichols, BAS, black: in the water, blue: planned) and floats (green) in the Weddell Sea west of the Greenwich Meridian. The extension of the network will occur in cooperation with Svein Osterhus frorm the Bjerknes centre in Bergen (Norway)

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ture

[°C

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Temperature and currents in the Warm Deep Water of the Weddell Sea derived from profiling

float data

Courtesy E. Fahrbach

Sea Mammal Research unit

MAMVis-AD

CEBC-CNRS

Kerguelen

Antarctica

1200 m

Maximum sea-ice extent (previous winter)

Winter Water

Sea temperature

SEaOS: Number of profiles

http://biology.st-andrews.ac.uk/seaos/index.html

SODB: 10513

Argo: 19463

SEaOS: 22230

Courtesy L. Boehme

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Sea-ice Buoys

New technology for observations in the sea-ice zone now being used in the Arctic Ocean. New developments appropriate for the Southern Ocean are needed.

Arctic example:http://www.whoi.edu/beaufortgyre/deployment2003/index.html#F19

METOCEAN expendable ice beacons suspend 3 SeaBird MicroCats at 15, 25 and 40 m depths interrogate each sensor twice per day, and broadcast the data via Argos, which also provides each drifter’s location. These ice drift timeseries are immediately made available to the IABP and GTS. The temperature and salinity data are updated daily on the BGFE website.

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Ice-Front Cruises

Ice-Front Moorings

Autonomous vehicles

Ice cavity monitoring stations: In situ

Radio Echo Soundingvia airplane

Phase-Sensitive Radar

Hot-Water Drilling

Topographic Soundings

Melting 12 tonnes of snow

Heaters and pumps

Hot-Water Drilling

Drill Stand

Courtesy of Keith Nicholls, B.A.S.

• The last SCAR/COMNAP meeting in 2006 brought together on an opportunistic basis a group of oceanographers, biologists and engineers, to examine the feasibility of establishing a Southern Ocean Observation System (SOOS) and in particular to investigate the possibility of incorporating data collected by marine mammals and seabirds. With reference to observation systems in the other oceans of the world, the importance of sustainable and coordinated observations was emphasized.

• SOOS planning workshop will be held in Bremen, Germany 1-3 October 2007

The Southern Ocean Observing System (SOOS)

http://www.clivar.org/organization/southern/expertgroup/SOOS.htm

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• Around 30 attendees representing “data providers” (CLIVAR, SOLAS, POGO, SCOR….) and “users” (COMNAP, WMO, NOAA…)

• Methodology:

Before: Each group to complete questionnaire in advance detailing e.g. observations of interest, gaps in areas of interest, priorities (short and long term)…

During: Break-out groups looking at different aspects of system. Plan outline and writing assignments

After: Circulation of plan to wider community (March 2008); Presentation of plan at SCAR open science conf. (July 2008); Finalise plan (Sept. 2008)

The Southern Ocean Observing System (SOOS)

http://www.clivar.org/organization/southern/expertgroup/SOOS.htm

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“Gaps” in the SO Observing System

• Transport Monitoring

• Glacier grounding line (relation to sea level rise). Support for InSAR mission (2010-2013…)

• Problems with air-sea reanalysis: need a better assessment of fluxes and errors in Southern Ocean region… atmospheric reanalysis:

Proposed SH regional atmospheric reanalysis (Bromwich et al.)

- Boundary layer component to improve fluxes

- Produce a validation and assessment of the quality of air-sea flux products in the SO region

- Resolve key processes (e.g. katabatic wind effects, topographic flow)

International efforts not coordinated, though components already exist

Arctic reanalysis is underway

Observational Techniques Grounding Line: Remote Sensing

Fast Recession of a West Antarctic Glacier E. J. RIGNOT

Satellite radar interferometry observations of Pine Island Glacier, West Antarctica, reveal that the glacier hinge-LINE position retreated 1.2 ± 0.3 kilometers per year between 1992 and 1996, which in turn implies that the ice thinned by 3.5 ± 0.9 meters per year. The fast recession of Pine Island Glacier, predicted to be a possible trigger for the disintegration of the West Antarctic Ice Sheet, is attributed to enhanced basal melting of the glacier floating tongue by warm ocean waters.

Science 24 July 1998:Vol. 281. no. 5376, pp. 549 - 551

Atmosphere Ocean

SLP/SAM

SLP/ENSOSLA/ENSO

SLA/SAM

Sallée et al. - Response of the ACC to atmospheric variability -

Southern Ocean Indices: The ACC system

Southern Ocean Indices

Covariance of PF and SAM or ENSO

Indian - SAM dominates

SE Pacific - ENSO dominates

ACC frontal system has complex response depending on region, not a simple ocean « mode » linked to a single atmospheric mode

Longitude

Covar.

Stratification indices1. At nominal 35°S locations in the South Atlantic, South Pacific, and Indian

Ocean, together with 2. AA peninsula and time-series stations in polar basins but significantly distant

from the source areas: - Weddell Gyre - Ross GyreIce indices3. Satellite sea-ice extent; thickness on repeat tracks4. Grounding line index (InSAR mission)Upper Ocean5. Shelf salinity in Ross Sea6. Mixed layer depth and salinityTransport(7. AA continental slope at 3 locations and northern Drake Passage)

Based on an assessment of IPCC runs, SO panel determines that stratification and watermass indices (e.g. north-south density differences) will be primary. The role of transport indices is still under investigation…

Southern Ocean Indices

1. Data-stream from animal-borne CTDs (e.g. SEaOS) is a new important component of observing system as is under-ice Argo. However, does not yet solve under-ice & polynya gaps - key areas for climate change

2. Importance of the Southern Ocean Observing System

3. Propose a “Global IPY-period synthesis”

4. Air-sea flux improvements in Southern Ocean region

5. Panel determines that stratification and water mass indices (e.g. north-south density differences) could be key. Focused transport indices required. More discussion/investigation needed…

OOPC Southern Ocean issues

The End…

http://woceatlas.tamu.edu/

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Additional Slides…

Modeling Techniques: Grounding Line Migration

Grounding line migration is a key process affecting the stability of marine ice sheets such as the West Antarctic Ice Sheet (WAIS).

Model predictions of grounding line migration and the cause and effect of changes in the grounding line are still UNSOLVED problems.

One reason for that is the lack of a widely agreed method of treating grounding line changes in numerical models.

Climate models do not include grounding-line processes, but MUST do so if they are to predict sea-level change.

Summary: Southern Ocean Region Panel

• The Panel recognizes that one of the largest uncertainties regarding future sea-level changes come from possible ice shelf/stream movement.

• The processes which control the location of the ice sheet edge are not properly represented in climate models. IPCC-type simulations normally do not allow for the evolution of the ice sheet and ocean boundary. One component controlling the location of grounding lines is the melt and freezing associated with convection in ice shelf cavities.

•We feel that progress may be made in reducing uncertainties of sea-level rise with a concerted effort to monitor the grounding line, representing the boundary between the ice sheet and the ocean. Measuring and modeling the characteristics of convection in ice-shelf cavities, calving, and the intersection of ice streams with the ocean are necessary parts of this effort.

• As a step in this direction we recommend establishing a remotely-sensed "grounding line index" based, for example, on Rignot et al. Eventually an operational system for monitoring the circumpolar location of the grounding line could be put into place and maintained.

• Another step is to create ocean and ice-sheet models capable of exchanging mass with one another, i.e., possessing a migrating grounding line capability.

Conclusions

• The development of ice compatible ARGO floats is (almost) completed

– ISA is ~80% successful

– iStore delivered first profiles

– RAFOS works fine for distances < 600 km

• The first fully ice compatible floats are now deployed

• Float and sound source network will be extended in international cooperation

• Preliminary analysis of the data confirms conclusions derived from CTD sections and allows to extend the regional analysis