SEG/AGU JOINT WORKSHOP

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SEG/AGU JOINT WORKSHOP

Enhanced Sea-Ice Thickness Retrieval

with Multi-Frequency Electromagnetic Devices

January 8, 2013

Priska Hunkeler

^1,2

, Stefan Hendricks

¹

, Andreas Pfaffhuber

³

, Malte Vöge

³

,

Rüdiger Gerdes

¹

1

2

3

Photo: David Ball, NRL

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o Motivation

o Development of MAiSIE

o First data

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o Motivation

o Development of MAiSIE o First data

Motivation

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Development

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First data

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Sea ice

nasa

Sea ice

Motivation

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Development

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First data

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nasa

Sea ice

Motivation

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Development

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First data

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nasa

Sea ice

Motivation

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Development

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First data

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Total ice plus snow thickness Freebord

Draft

AWI

ESA

R.Ricker, AWI D.Ball, NRL

CDR

Sea-ice thickness

Sea ice Ocean water Direct methods

Indirect methods

Motivation

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Development

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First data

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Airborne Electromagnetics (AEM) - 1D approach

after Hendricks, 2009 Method is based on the contrast of electrical conductivity between ocean water and sea ice

h_l Measured with laser altimeter

h₀ Secondary H_Sto primary H_P magnetic field (Phase and Amplitude, In-phase and Quadrature) can be related to h₀

h₀ - h_l Sea-ice thickness Z footprint

Holladay et al. 1990

H_S H_P

Motivation

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Development

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First data

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1D approach

Motivation

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Development

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First data

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1D approach

Motivation

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Development

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First data

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1D approach

Motivation

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Development

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First data

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1D approach

Water Sea ice

Ice

platelet

S. Günther, 1999

ISW: Ice Shelf Water

mWDW: modified Warm Depth Water S. Günther, 1999

Sea floor

Ekstrøm ice shelf

Formation of platelet ice

Sea ice

Motivation

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Development

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First data

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S. Hendricks

Pitch

Yaw Roll

Frequency Broadband 0.5-8 kHz

 Variable sounding depth

NGI, 2012

2D approach

 3D

information about

sea ice

Temperature Measurements inside the EM- Bird (receiver, amplifier,…)

 Better control of typical error sources Attitude

3 axis receiver

Motivation

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Development

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First data

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Summary MAiSIE

M A i S I E

Broadband 0.5 - 8 kHz

3 component receiver

GPS, INS, temperatures, space

for laser scanner

2.5D FE inversion

Existing AWI systems

1 frequency (4 kHz)

1 component

receiver GPS 1D processing

Motivation

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Development

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First data

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Summary MAiSIE

M A i S I E

Broadband 0.5 - 8 kHz

3 component receiver

GPS, INS, temperatures, space

for laser scanner

2.5D FE inversion

Existing AWI systems

1 frequency (4 kHz)

1 component

receiver GPS 1D processing

o 1D representation of sea ice o One sea ice layer

o Underestimation of sea-ice pressure ridges

o 2D representation of sea ice  smaller scale than footprint o One or more ice layers with variable conductivities

o Better control of typical error sources (attitude error, nonlinear system drift)

Motivation

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Development

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First data

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SIZONet campaign Barrow, Alaska

April 2012 First tests with MAiSIE

Polarstern cruise Arctic Ocean

August-October 2012

Motivation

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Development

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First data

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o Raw data, 4090 Hz

o Temperature measurements inside the EM-sensor  Improvements of signal quality and drift correction

Field campaign SIZONet in Barrow, Alaska (April 2012)

Amplitude [nT] Phase [deg]

Source height [ft] Temperature [°C]

Motivation

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Development

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First data

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Field campaign SIZONet in Barrow, Alaska - Data quality

o 4090 Hz

o Drift corrected data

o Comparison of 1D model and data over sea ice and open water

o 1D model: EM response over homogeneous half space, solving of hankel transform after W.L. Anderson, 1970.

Motivation

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Development

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First data

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Open water Field campaign SIZONet in Barrow - Data quality

o 1D sea ice thickness for different

frequencies over sea ice and open water

o Higher frequencies are within ± 10cm over open water

Motivation

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Development

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First data

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Inversion software NGI “ngi25em”

o 1D and 2.5 D FE forward model are in good agreement (<10ppm)

o Adapt “ngi25em” to airborne EM sea ice case

o Mesh for forward model, different

positions of receiver and transmitter

Motivation

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Development

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First data

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NGI, 2012

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Weddell Sea

Atka Bay

Field campaign SIMBIS, November 2012, Atka Bay, Antarctic

Motivation

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Development

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First data

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o Detection of platelet ice with the multi- frequency handheld EM device GEM-2 o Validation data sets from drillings, under-

ice inspection system, ice cores

o AEM campaign with MAiSIE in Weddell Sea 2013

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Transect GEM-2, Atka Bay

TerraSAR-X 15.11.2012

Motivation

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Development

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First data

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Upcoming field campaign November 2012 in the Antarctic Transect GEM-2, Atka Bay

5310 Hz

18330 Hz

63030 Hz

93090 Hz

Motivation

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Development

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First data

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o Grid over ridge structures

o GEM-2 data processing (any experiences?)

o AEM campaign in 2013 GEM-2, Atka Bay

8 m

Motivation

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Development

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First data

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Summary and Outlook

Hardware

o MAiSIE hardware changes: Reducing drift und noise Data analysis

o Correcting for pitch, roll and yaw o Completion of inversion software o Processing of existing AEM data sets o Processing of GEM-2 data set

Campaigns

o AEM campaigns 2013 (Barrow and Weddell sea)

AEM MAiSIE multi-frequency and multi-component datasets o Barrow 2012

o Central Arctic Ocean 2012

GEM-2 multi-frequency dataset (platelet ice, ridge) o Atka Bay 2012

SUMMARYOUTLOOK

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Thank you