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Brine flow through sea ice

Entry ID: ASAC_1060

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Summary

Abstract: Metadata record for data from ASAC Project 1060
See the link below for public details on this project.

Taken from the referenced publications:

Sea ice exhibits a marked transition in its fluid transport properties at a critical brine volume fraction Pc of about 5 percent, or temperature Tc of about -5 degrees Celsius for salinity of 5 parts per thousand. For ... temperatures warmer than Tc brine carrying heat and nutrients can move through the ice, whereas for colder temperatures the ice is impermeable. This transition plays a key role in the geophysics, biology, and remote sensing of sea ice. Percolation theory can be used to understand this critical behaviour or transport in sea ice. The similarity of sea ice microstructure to compressed powders is used to theoretically predict Pc of about 5 percent.

The snow cover on Antarctic sea ice often depresses the ice below sea level, allowing brine or seawater to infiltrate, or flood the snowpack. This significantly reduces the thermal insulation properties of the snow cover, and increases the ocean/atmosphere heat flux. The subsequent refreezing of this saturated snow or slush layer, to form snow-ice, can account for a significant percentage of the total ice mass in some regions. The extent of saturated snow cannot presently be estimated from satellite remote-sensing data and, because it is often hidden by a layer of dry snow, cannot be estimated from visual observations. Here, we use non-parametric statistics to combine sea-ice and snow thickness data from drillhole measurements with routine visual observations of snow and ice characteristics to estimate the extent of brine-infiltrated snow.

During a field experiment in July 1994, while the R.V. Nathaniel B. Palmer was moored to a drifting ice floe in the Weddell Sea, Antarctica, data were collected on the sea-ice and snow characteristics. We report on the evolution of ice which grew in a newly opened lead. As expected with the cold atmospheric conditions, congelation ice initially formed in the lead. Subsequent snow accumulation and large ocean heat fluxes resulted in melt at the base of the ice, and enhanced flooding of the snow on ice surface. This flooded snow subsequently froze, and, five days after the lead opened, all the congelation ice had melted and twenty-six centimetres of snow ice had formed. We use measured sea-ice and snow salinities, thickness and oxygen isotope values of the newly formed lead ice to calculate the salt flux to the ocean. Although there was a salt flux to the ocean as the ice initially grew, we calculate a small net fresh-water input to the upper ocean by the end of the 5 day period. Similar processes of basal melt and surface snow-ice formation also occurred on the surrounding, thicker sea ice. Oceanographic studies in this region of the Weddell Sea have shown that salt rejection by sea-ice formation may enhance the ocean vertical thermohaline circulation and release heat from the deeper ocean to melt the ice cover. This type of deep convection is thought to initiate the Weddell polynya, which was observed only during the 1970s. Our results, which show than an ice cover can form with no salt input to the ocean, provide a mechanism which may help explain the more recent absence of the Weddell polynya.

Related URL

Link: VIEW PROJECT HOME PAGE

Description: Public information for ASAC project 1060

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: -60.0

S: -68.0

E: 5.0

W: -20.0

Temporal Coverage

Start Date: 1994-07-01

Stop Date: 1994-08-31

Location Keywords

OCEAN > SOUTHERN OCEAN

CONTINENT > ANTARCTICA

GEOGRAPHIC REGION > POLAR

OCEAN > SOUTHERN OCEAN > WEDDELL SEA

Science Keywords

CRYOSPHERE > SEA ICE > PACK ICE

CRYOSPHERE > SEA ICE > POLYNYAS

ISO Topic Category

OCEANS

Platform

SHIPS

R/V NBP > R/V Nathaniel B. Palmer

Quality Values provided in temporal and spatial coverage are approximate only.

Access Constraints PDF copies of the referenced papers are available for download by AAD staff at the provided URL.

Use Constraints This data set conforms to the PICCCBY Attribution License
(http://creativecommons.org/licenses/by/3.0/).

Please follow instructions listed in the citation reference at the provided URL when using these data.

Ancillary Keywords

sea-ice

Nathaniel B. Palmer

Data Set Progress

COMPLETE

Data Center

Australian Antarctic Data Centre, Australia

Data Center URL: http://data.aad.gov.au

Data Center Personnel
Name: DATA OFFICER AADC Phone: +61 3 6232 3244 Fax: +61 3 6232 3351 Email: metadata at aad.gov.au Contact Address: Australian Antarctic Division 203 Channel Highway City: Kingston Province or State: Tasmania Postal Code: 7050 Country: Australia

Distribution

Distribution Media: HTTP

Distribution Size: 7.90 MB

Distribution Format: PDF

Fees: Free

Personnel

VICTORIA LYTLE

Role: INVESTIGATOR

Role: TECHNICAL CONTACT

Role: DIF AUTHOR

Phone: +61 3 6226 7652

Email: vicky.lytle at aad.gov.au

Contact Address:

GPO Box 252-80

Antarctic CRC

City: Hobart

Province or State: Tasmania

Postal Code: 7001

Country: Australia

Creation and Review Dates

DIF Creation Date: 2004-11-09

Last DIF Revision Date: 2005-12-29

Future DIF Review Date: 2005-08-13

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