Laptev Sea landfast ice: Probing a frozen estuary with SAR

H. Eicken1, I. Dmitrenko2, K. Tyshko3, A. Darovskikh3, W. Dierking4, U. Blahak1, J. Groves1, H. Kassens51: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA2: International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, USA3: Arctic and Antarctic Research Institute, St. Petersburg, Russia4: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany5: Geomar Forschungszentrum, University of Kiel, Kiel, Germany

• Introduction- Fluxes of freshwater and dissolved/particulate across the Siberian shelves - Study area in the Laptev Sea

• The Lena Delta- Anatomy of the delta and ice cover- Probing the ice cover with SAR

• The Laptev Sea as a frozen estuary- Zonation of the landfast ice cover- Contribution of riverine water to ice mass balance- Under-ice mixing and freshwater dispersal

• Conclusions

The Arctic coastal zone as a multi-phase boundary

Pack iceLandfast ice 1s to 100s km

Flaw lead 1s to 10s km

Bottomfast ice

Ice entrainment and export of sediments

Aeolian transport and deposition

Deposition on fast ice (river flooding etc.)

Incorporation of (re)suspended particulate matter (suspension freezing)

Anchor-ice formation

Bottom adfreezing

Release from melting sea ice

Small-scale redistribution

Annual transport of sediment and organic carbon by sea ice

Shown are best estimatesfor annual fluxes of - sea ice (in km3)- particulates transportedby sea ice (in Tg = 106 t)

- terrestrial organic carbontransported by sea ice(in Gg = 103 t)

Maximum particulatetransport demonstratedfor individual iceentrainment events (LaptevSea):18 Tg (18 x 106 t)

490 km3 FW

The Arctic coastal zone as a multi-phase boundary

Brine rejection

Riverine freshwater input

Pack iceLandfast ice 10s to 100s km Flaw lead

1s to 10s kmBottomfast ice

30 Si > 5

Freshwater/brackish ice (10-30 km)Sw - 5 Si

Bottomfast ice: Ice bonding and coastal morphology

Reimnitz, 2002

Laptev Sea study area

Freshwater: 600 km3/yr

SPM: 21x106 t/yr

Sea ice: 550 km3/yr

SPM: ??x106 t/yr

SPM: 50x106 t/yr

Sea ice: 150 km3/yr SPM:

??x106 t/yr

SPM: 29x106 t/yr

Freshwater: 190 km3/yr

Laptev Sea

East Siberian Sea

Lena, Yana, Olenek

Indigirka, Kolyma

Coastal erosion

Sea-ice formation & export

100 m

Data sources: Are, 1999, Gordeev et al., 1996, Timokhov, 1994, Eicken et al., 1997

Laptev Sea study area

Landfast ice edge 1999

1997

2.08m 63% (C1)

2.20 m 88% (C8)

1.68m 59% (C3)

0.92m 55% (C2)

1.39m 56% (C11)1.60m

59% (C4)

1.71m 62% (C7)

1.67m 60% (C5)

2.05m 57% (C9)

1.08m 57% (C10)

0.68 m 45%* (C6)

2.07m 73%* (C1A)

Cape Buorkhaya Yana Bay

KotelnyyLe

na

Lena Delta

Lena Delta sea ice and processesA

B

D

10 m

10 m

CS1

S2S3

TIKSI

Bykov Channel

Trof

imov

Cha

nnel

s

EK1

Radarsat ScanSAR Wide, March 5, 1997, incidence angle 45-50˚

Transition between brackish and sea ice, Surface salinities, Nov. 1996(data courtesy of I. Semiletov)

River channels and nearshore ridging (with containment of freshwater)

Backscatter signa-tures and textures

0.08

0.04

0.00

f(σ

o )

-40 -20 0σo , dB

-50 -50

-40 -40

-30 -30

-20 -20

-10 -10

σo ,

dB

1208040Day of year (1997)

-40 -20 0σo , dB

0.08

0.04

0.00

σf(

o )

-50 -50

-40 -40

-30 -30

-20 -20

-10 -10

σo ,

dB

1208040Day of year (1997)

0.08

0.00

0.04f(σ

o )

-40 -20 0σo , dB

-50 -50

-40 -40

-30 -30

-20 -20

-10 -10

σo ,

dB

1208040Day of year (1997)

1.5

1.0

0.5

0.0

Dep

th, m

102101100Brine vol. fraction, ‰

0.08

0.04

0.00

f(σ

o )

-40 -20 0σo , dB

-50

-40

-30

-20

-10

-50

-40

-30

-20

-10

σo ,

dB

1208040Day of year (1997)

1.5

1.0

0.5

0.0

Dep

th, m

102101100Brine vol. fraction, ‰

1.5

1.0

0.5

0.0

Dep

th, m

102101100Brine vol. fraction, ‰

Brine vol. fraction, ‰

1.5

1.0

0.5

0.0

Dep

th, m

102101100

Sub-region A

Sub- region B

Sub-region C

Sub-region D

Backscatter signatures and textures

2.2

2.0

1.8

1.6

1.4

1.2

NG

LDM

ent

ropy

1601208040NGLDM second moment

A B C D

Dielectric properties and penetration in FW/brackish/sea ice

Hallikainen & Winebrenner (1992)

Dielectric properties and backscatter signatures of FW/brackish/sea ice

• Sea-ice growth/salt-flux modeling for different surface water salinities- finite-difference scheme ice growth model - coupled to salt-flux model based on Cox & Weeks (1988)- stable-isotope fractionation model (Eicken, 1998)- forced by weather station data for Tiksi (southcentral Laptev Sea

• Sea-ice backscatter modeling- Integral Equation Model for surface scattering, Independent RayleighScattering Model for volume scattering (Fung, 1994)- ice cover represented by four layers of varying salinity and temperature,based on field measurements and ice-growth model simulations- dielectric properties from empirical data for complex dielectric permittivityfrom Hallikainen & Winebrenner (1992)- ice surface and bottom roughnesses based on data for smooth, level first-year ice as supported by field observations; size of scatterers (gas and brine inclusions) field observations and data compilations

Dielectric properties and backscatter signatures of FW/brackish/sea ice

Scattering contributions of ice-water interface for freshwater ice in winter(varying correlation length l and rms-height s)

-50

-40

-30

-20

-10

15 20 25 30 35 40 45 50 55 60

l=9cml=3cm

HH-Pol.

s=10mm

s=1mm

s=0.5mm

s=8mm

s=3mm

Incidence Angle [deg]

Back

scatt

erin

g Co

effi c

i en t

[dB ]

Ice-Water-Interface

Dielectric properties and backscatter signatures of FW/brackish/sea ice

-28

-26

-24

-22

-20

-18

-16

σo, d

B

2520151050Salinity (psu)

Winter Summer Field data

Lena Delta sea ice and processesA

B

D

10 m

10 m

CS1

S2S3

TIKSI

Bykov Channel

Trof

imov

Cha

nnel

s

EK1

Radarsat ScanSAR Wide, March 5, 1997, incidence angle 45-50˚

Transition between brackish and sea ice, Surface salinities, Nov. 1996(data courtesy of I. Semiletov)

River channels and nearshore ridging (with containment of freshwater)

Detecting bottomfast ice with SAR

A: Dec. 13, 1996 5.5 km2

B: Jan. 16, 1997 51.0 km2

C: April 29, 1997 77.0 km2

D: May 23, 1997 89.8 km2

2.0

1.5

1.0

0.5

0.0

Ice

thic

knes

s, m

500450400350300Days since Jan 1 of Year 1 of growth season

Climatology 1996/97 1998/99 Freshwater ice ('98/'99) Site 3 ('98/'99) Site 11 ('98/'99)

Changes in bottomfast ice regime: Reduced ice thickness

2.0

1.5

1.0

0.5

0.0

Ice

thic

knes

s, m

500450400350300Days since Jan 1 of Year 1 of growth season

Climatology 1996/97 1998/99 Freshwater ice ('98/'99) Site 3 ('98/'99) Site 11 ('98/'99)

Zonation of landfast ice

Landfast ice edge 1999

1997

2.08m 63% (C1)

2.20 m 88% (C8)

1.68m 59% (C3)

0.92m 55% (C2)

1.39m 56% (C11)1.60m

59% (C4)

1.71m 62% (C7)

1.67m 60% (C5)

2.05m 57% (C9)

1.08m 57% (C10)

0.68 m 45%* (C6)

2.07m 73%* (C1A)

Cape Buorkhaya Yana Bay

KotelnyyLe

na

Lena Delta

Landfast ice core properties

Landfast ice core properties: Riverine water fraction from δ18O

-20

-15

-10

-5

0

δ18 O

, ‰

302520151050Salinity, ‰

Ice samples (Fall 1995) Water samples (Fall 1995) Atl. water/Lena regression Regression (water samples) 1999 ice samples

Atl.

Lena

Landfast ice core properties

Table 1: Landfast i ce core data

Site Sampl. d ate zi, m Si, ‰ δ18O, ‰ friv, % zalign, m Alignm. date

1 4/17/99 2.08 2.6 –10.5 63 1.00 12/22/981A 4/17/99 2.07 2.0 73*2 5/6/99 0.92 4.0 –8.9 55 0.70 4/5/993 4/21/99 1.68 3.6 –9.7 59 1.35 2/18/994 4/23/99 1.60 4.7 –9.6 59 0.80 n/a (drift ice)5 4/24/99 1.67 3.6 –9.8 606 (8) 4/26/99 0.68 5.6 45* 0.30 n/a (drift ice)7 4/27//99 1.71 4.2 –10.3 628 4/30/99 2.20 0.5 –15.6 88 n/a (freshwater ice)9(16) 4/30/99 2.05 4.4 –9.1 57 1.70 3/14/9910(18) 5/1/99 1.08 4.3 –9.3 57 0.80 3/23/9911(24) 5/6/99 1.39 3.8 –9.0 56 0.90 3/17/99

zi – ice thickness, S i – ice salinity, friv – fraction o f riverine water (*based on i ce salinityonly), zalign – depth of first azimuth al crystal alignment

The Arctic coastal zone as a multi-phase boundary

Brine rejection

Riverine freshwater input

Pack iceLandfast ice 10s to 100s km Flaw lead

1s to 10s kmBottomfast ice

30 Si > 5

Freshwater/brackish ice (10-30 km)Sw - 5 Si

Landfast ice: Under-ice plume spreading

2.0

1.5

1.0

0.5

0.0

Ice

thic

knes

s, m

500450400350300Days since Jan 1 of Year 1 of growth season

Climatology 1996/97 1998/99 Freshwater ice ('98/'99) Site 3 ('98/'99) Site 11 ('98/'99)

Under-ice plume spreading (freshwater volumes preliminary data!)

RFW input: 93 km3

RFW export: –118 km3

RFW freezing: –125 km3

RFW at start of winter: 400 km3

RFW at end of winter: 250 km3

RFW spreading

rate

1.3 to 2.7 cm s–1 1.0 cm s

–1

Core 8 Core 1

Winter

RFW input: 393 km3

RFW export: –368 km3

RFW from ice melting: 125 km3

RFW at start of summer: 250 km3

RFW at end of summer: 400 km3

Summer

Under-ice plume spreading and the role of ice roughness

• under-ice plume spreading in Laptev Seat larger than under Mackenzie shelf ice cover by up to one order of magnitude• critical role of ice roughness• field observations and Radarsat SAR scenes indicate general lack of deformed ice and prominent ridges in Laptev Sea landfast ice

Under-ice plume spreading and the role of ice roughness

• ERS-Scatterometer data show lowestbackscatter coefficient for Laptev Sea

April 19-25, 1999

Under-ice plume spreading and the role of ice roughness

April 19-25, 1999

Conclusions

• SAR helps probe variability patterns in frozen estuarine systems(sensitive to 1‰ sea-ice or 5 psu surface-water salinity contour; potential utility of multi-frequency (L-Band!), polarimetric SAR

• Value of SAR in monitoring bottom-fast sea ice in estuarine regions; significant discrepancies between current understanding and observations in extent of bottomfast ice need to be resolved

• Laptev Sea landfast ice composed to 60 % of riverine freshwater;impact of river discharge on ice mass balance and ice-mediated coastal processes (erosion, aggradation etc.)

• As much as 1/3 of annual riverine discharge into Laptev Sea locked up in landfast ice (compare to