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Sea Ice Mass Balance in the Antarctic - Shipboard Electro-Magnetic induction (EMI) Ice Thickness

Entry ID: SIMBA_Shipboard_EMI_Ice_Thickness

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Summary

Abstract: EMI (electromagnetic induction) records of ice thickness, utilized a Geonics EM-31 induction meter, were conducted with the meter suspended from the ship’s starboard A-frame, at heights varying from 2.5 to 4.0 meters. Conductance data (in millisiemens/meter) were acquired at 2 second intervals. Heights to the snow/ice surface were measured with a sonic ranger attached to the frame housing the ... EMI device. Data were recorded on a Campbell Scientific CX200 data logger (range measurements) and with Allegro Windows CX handheld computer (conductivity data) running Geonics EM31 acquisition software. Due to design constraints with the CX200 data logger, range measurements were only acquired at 60 second intervals. Range measurements were adjusted for speed of sound variation due to temperature. Geolocation of EMI/ranger data pairs was accomplished through simultaneous logging of the ships GPS track at a mean positional accuracy of &amp;amp;amp;lt; 3.0 meters. The data set includes EMI records of ice thickness along an outbound track from Palmer Station commenced 8 September at 18:49 GMT, at 64.48S 64.03W and terminated 9 September at 04:00 GMT at 64.53S 65.00W. However, due to uncertainties of conductivity measurements in predominately pancake ice conditions (&amp;amp;amp;lt; 100% ice concentration), ice thicknesses for this track will not be reported. The dataset also includes EMI records of ice thickness along an inbound track to Belgica Station commenced 25 September at 13:00 GMT, at 69.78S 90.02W and terminated 27 September at 3:41 GMT at the conclusion of way station 3 operations, due to high winds that persisted the remainder of the day. An estimated 90 kilometers of EMI data were collected along this inbound track. A frequency histogram of ice thickness measurements (n=957) along inbound track to Ice Station Belgica was constructed. During the journey out to the ice edge, the EM-31 was again deployed from the starboard A-frame to collect ice thickness data during transit. This transit began at approximately 69°55’S 93°45’W and extended to 68°50’S 90°12’W, a distance covered of 216 km. A digital surveillance camera was added to the instrumentation on the kayak to record images of the EM footprint (target ice) concurrent with the conductivity measurements. This video record was used in analyses to correct ice thickness determinations for varying ice concentration.

The Ice Thickness by Ship-borne Electromagnetic Induction (EMI) data provided plots of calibration values and fitted exponential models. Calibration of EMI conductance for instrument height was conducted using the open water method. Twenty two conductance measurements were acquired over open water (an ice lead at Palmer Station) at heights ranging from 4.2 to 0.6 meters, as acquired from an on-board distance ranger. All conductance values at heights over 1.4 meters (corresponding to the right flank of the theoretical curve) were fit to an exponential model. Y= 840.85e^(-.4947x), where y is conductance in millisiemens/meter, and x is instrument height (or distance to sea water). This equation was subsequently inverted to generate distance from seawater from conductivity measurements acquired in underway operations. A plot of calibration values and the fitted calibration curve can be found in the data set.

Purpose: Ice thickness values in continuous tracks in the Antarctic sea ice zone obtained here are important for determining the ice thickness variations over distances of tens of kilometers. Measurements made on ice floes by drilling provide important calibration points but the areal distribution of ice thickness can only be determined by these shipborne methods, and these are commensurate with the scale of satellite remote sensing imagery and the grid resolution of sea ice models.

Related URL

Link: VIEW PROJECT HOME PAGE

Geographic Coverage

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Spatial coordinates

N: -61.85

S: -70.68

E: -64.05

W: -94.85

Parent DIF

This data set description is a member of a collection. The collection is described in
Project ID: SIMBA Drift Station

Temporal Coverage

Start Date: 2007-09-01

Stop Date: 2007-10-31

Location Keywords

CONTINENT > ANTARCTICA

GEOGRAPHIC REGION > POLAR

OCEAN > SOUTHERN OCEAN > BELLINGSHAUSEN SEA

Science Keywords

CRYOSPHERE > SEA ICE > ICE DEPTH/THICKNESS

CRYOSPHERE > SNOW/ICE > ICE DEPTH/THICKNESS

OCEANS > SALINITY/DENSITY > CONDUCTIVITY

OCEANS > SEA ICE > SNOW DEPTH

ISO Topic Category

CLIMATOLOGY/METEOROLOGY/ATMOSPHERE

ENVIRONMENT

OCEANS

Platform

SV > Snow Vehicle

GPS > Global Positioning System Satellites

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

Instrument

EMIS > ELECTROMAGNETIC INDUCTION SENSORS

Project

NSF/OPP > Office of Polar Programs, National Science Foundation

IPY > INTERNATIONAL POLAR YEAR

Access Constraints None

Ancillary Keywords

SHIP-BASED SEA ICE OBSERVATIONS THROUGH EMI

Data Set Progress

IN WORK

Originating Center

Laboratory for Remote Sensing and Geoinformatics UTSA

Data Center

National Snow and Ice Data Center

Data Center URL: http://nsidc.org

Data Center Personnel
Name: STEPHEN ACKLEY Phone: +1 1 210 341 6556 Email: sackley at pol.net, Stephen.ackley at utsa.edu Contact Address: 118 W Castle Ln City: San Antonio Province or State: Texas Postal Code: 78213 Country: USA

Data Center Personnel
Name: NSIDC USER SERVICES Phone: +1 (303) 492-6199 Fax: +1 (303) 492-2468 Email: nsidc at nsidc.org Contact Address: National Snow and Ice Data Center CIRES, 449 UCB University of Colorado City: Boulder Province or State: CO Postal Code: 80309-0449 Country: USA

Personnel

STEPHEN ACKLEY

Role: INVESTIGATOR

Phone: +1 1 210 341 6556

Email: sackley at pol.net, Stephen.ackley at utsa.edu

Contact Address:

118 W Castle Ln

City: San Antonio

Province or State: Texas

Postal Code: 78213

Country: USA

JESSICA JIMENEZ

Role: DIF AUTHOR

Phone: 956-451-9288

Email: Jessica.jimenez_eng at yahoo.com

Contact Address:

3407 Ivy Ave

City: Hidalgo

Province or State: Texas

Postal Code: 78557

Country: USA

Publications/References

Xie, H., S.F. Ackley, D. Yi, H.J. Zwally, P. Wagner, B. Weissling, M. Lewis, K. Ye (May 2011), Sea ice thickness distribution of the Bellingshausen Sea from surface measurements and ICESat altimetry, Deep Sea Research Part II, 58, 9-10, 1039-1051, doi:10.1016/j.dsr2.2010.10.038, http://www.sciencedirect.com/science/article/pii/S0967064510003255

Creation and Review Dates

DIF Creation Date: 2012-02-16

Last DIF Revision Date: 2012-04-20

Future DIF Review Date: 2012-02-16

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