St.Petersburg, 27-28 September 2013 Fr-Ru seminar «Vostok » Results of the new 5G-1N ice core studies related to technology of Lake Vostok unsealing V

St.Petersburg, 27-28 September 2013Fr-Ru seminar «Vostok »

Results of the new 5G-1N ice core studies related to technology of Lake

Vostok unsealing

V. Lipenkov, N. Vasiliev, A. Ekaykin, I. AlekhinaAARI, St. Petersburg, St. Petersburg Mining University

RADARSAT CSA

Vostok


Lake Vostok - an essential element of the Antarctic subglacial environments:

• Surface area ~16,000 km2

• Lake volume ~6,000 km3 (~25% of the total volume of water beneath the Antarctic ice sheet)

• Water depth up to 1200 m• Thickness of the overlying ice

sheet up to 4350 m• A deep depression (1600 m

b.s.l.) in the southern part of the lake

Popov et al., 2011

Siegert at al., 2007

Aquatic environments beneath the Antarctic ice sheet (>22,000 km3 of water in >370 sub-ice lakes) provide a unique natural laboratory for prolonged ecological experiments


Lake Vostok and the Vostok drilling projectHole 5G setting

3460

3500

3540

-600

-400

-200

0

200

-60 -40 -20 0 20Distance from hole 5G (km )

1000

2000

3000

He

igh

t abo

ve s

ea

leve

l (m

)

5 G

5G -1

5 G -2

Lake Vostok

Lake ice 1

Lake ice 2

M eteoric ice

Met

. ic

eL

ake

ice

1L

ake

ice

2

W ater

3537

3618

3769

De

pth

(m)

Age

(ky

r)

40

25

0

VFL

Vostok

10 km

Original plan for Lake Vostok unsealing

3740

3750

3770 m

3720

Accreted (lake)

ice

Lake Vostok

Uncertainties , risks and problems:

Ice sheet thickness: 3720-3790 m (Popkov, 1998; Popov, 2003; Richter et al., 2008)

Pressure melting temperature of ice: from -2.85 to -2.62 °C

Concentration of gases in subglacial water: 0.09-2.7 liters (STP) of gas per kg of water (Lipenkov & Istomin, 2001)

Is the ice sheet in hydrostatic equilibrium at the drilling site? (e.g., Wendt, 2005; Ewert et al., 2012)

Potential for contamination

Potential for degassing of lake water allowed to rise in the hole

Fluid control: “the control of all inflows, outflows and movements of fluid at all points in the hole and the ability to stop an inflow of fluid “as desired” (Fleckenstein, 2006)

Madison, WI, USA 9-13 September 2013

Narrative of the deep drilling operationsat Vostok Station since 2007

5 G

Lake Vostok

M eteoric ice

Lake ice

0 Jan 1990

3538

3769.3

De

pth

(m

)

2502 (1991)

5 G

5 G -1

5 G -1

Lake Vostok

M eteoric ice

Lake ice

0 Jan 1990

3538

3769.3

De

pth

(m

)

3666 (O ct 2007)

2502 (1991)

2240 (1992)5 G

5 G -1

5 G -1

5 G -2

Lake Vostok

M eteoric ice

Lake ice

0 Jan 1990

3538

3769.3

De

pth

(m

)

3666 (O ct 2007)

2502 (1991)

2240 (1992)

3600 (Feb 2009)

Feb 2012

5 G

5 G -1

5 G -1

5 G -2

Lake Vostok

M eteoric ice

Lake ice

0 Jan 1990

3538

3769.3

De

pth

(m

)

3194 (D ec 2012)

3666 (O ct 2007)

2502 (1991)

2240 (1992)

3600 (Feb 2009)

Feb 2012

5 G

5 G -1

5 G -1

5 G -2

5 G -1 N

Lake Vostok

M eteoric ice

Lake ice

0 Jan 1990

3538

3769.3

De

pth

(m

)

3194 (D ec 2012)

3415

3458

3666 (O ct 2007)

2502 (1991)

2240 (1992)

3600 (Feb 2009)

Feb 2012

5 G

5 G -1

5 G -1

5 G -2

5 G -3

5 G -1 N

Lake Vostok

M eteoric ice

Lake ice

0 Jan 1990

3538

3769.3

De

pth

(m

)

3194 (D ec 2012)

3415

3458

3543,6 (Feb 2013)

3666 (O ct 2007)

2502 (1991)

2240 (1992)

3600 (Feb 2009)

Feb 2012


Penetration record from the last 5G-2 run

Fluid level before drilling: 50 mEstimated fluid level during drilling: 25…30 mFluid level 8 days after penetration: 43 m

Fluid outflow from the hole mouth started 1 min after the penetration and persisted for 5 min (total fluid loss through the hole mouth 1-2 m3)

Rate of fluid rise ≤ 0.4 м/s


The last ice core from hole 5G-2

#3 #3

3608 m

20 mLV 3D circulation modelKazko et al., 2012

Beneath Vostok Station:Upwelling ≤ 0.1 mm/sMaximum size of particles in suspension 10-15 m

Madison, WI, USA 9-13 September 2013

3194 m – hole reaming start

3200 m – first cork of bright white hard material

3385 m – first crescent-shaped fragments of refrozen water ice

3415-3427 m – mixed clathrate hydrate of lake gases and hydrochloroflurocarbon densifier (HCFC-141b) fills ~ 30% of the hole volume

Ice core studies (5G-1N and 5G-3 holes)


3424-3427 m –

hydrate core inside refrozen water ice core

80 0 mm



3427-3458 m – “solid” water ice (refrozen lake water):

-radial ice structure with preferred horizontal orientation of c-axes

-concentric layering implies several stages in ice growth

- many gas and liquid inclusions, concentration of which increases toward 5G-1 hole axis

- refrozen water ice easily come off a hole wall (hydrate layer)



5G-1 hole wall, depth 3599 mObtained by drilling branch hole 5G-2

5G-1 hole wall, depth 3436 mObtained by redrilling 5G-1 (5G-1N) hole)



Water level fluctuation after lake unsealing

5 G

5 G -1

5 G -1

5 G -2

5 G -3

Lake Vostok

M eteoric ice

Lake ice

0

33853427

3538

3769.3

Ice

core

dep

th (

m)

Max

imu

m w

ate

r h

eig

ht

(382

m)

He

igh

t o

f s

olid

wa

ter

ice

(3

40 m

)

3194

3415

3458

3543,6

3666

2502

2240

3600

5 G -1 N

3759

Vostok 2012EDML 2006

b

Ice-coated units of the drill pulled out from the borehole:EDML ice core Vostok ice core


3426m

Hydrate center

Core with hydrate center


Drilling fluid components in the water ice corefrom hole 5G-1N

Composition of the drilling fluid (sample from 3630 m depth), %:

Aliphatic hydrocarbons - 45.0

Naphthene hydrocarbons - 23.0

Aromatic hydrocarbons - 27.8

Hydrochloroflurocarbone (HCFC-141b) – 3.2

Ethylene glycol <0.03

Unidentified -1

= kerosene

+

densifier

+

Refrozen water ice:Total concentration of DF components ~15 % (volume)

Hydrate core: 4% of core volume:DF components ~15%, but HCFC-141b is increased by factor of 2

Meteoric iceHydrate layer

Refrozen water ice:Concentration of DF components ~16 mg/l

Central channel:HCFC-141b ~15 mg/lPhenol congeners ~35 mg/l And NO KEROSENE!

3426 m

3436 m

Central channel3436 m

3450m

Peripheral core part

Elemental analysis - increased concentrations of some elements (Na, Mg, Si, S, K, Fe – level of some mineral waters with low salt content)

Concentration factor – 30-50 No any firm conclusions about the composition of the lake water. contamination samples with DF

St.Petersburg, 27-28 September 2013Fr-Ru seminar «Vostok»

0,0001

0,001

0,01

0,1

1

10

3420 3425 3430 3435 3440 3445 3450 3455

Глубина (м)

Нап

ряж

ени

е (В

)

наружная часть столба замерзшей озерной воды

вблизи центрального

канала

переход к белесому(гидратному?) слою и атмосферномульду


канала

средняя часть столба замерзшей озерной воды

центральныйканал

атмосферный лед


канала

Depth

Vol

tage

(V

)

Outer part of secondary frozen lake

water

Meteoric ice

Central channelCentral channel

Vicinity of central channel



Transit to hydrate layer and meteoric ice

Midpoint of secondary frozen lake water core

Electro conductivity of secondary lake ice


- Ice sheet thickness: 3759±3 m (Pice= 33.70±0.03 MPa)

- Pressure melting temperature at the bottom (most probable value): -2.67 °C

- Concentration of dissolved gases in the surface layer of lake water (m.p.v): 0.7 litre/kg, far from the equilibrium with hydrate phase

- Poor mixing of the source (melt) water with resident water of the main lake body

- Hydrostatic imbalance, if exists, can not be resolved because of the large uncertainties of the drilling fluid pressure estimates

- A series of reactions may occur between subgalcial water rising in the hole and different components of the drilling fluid

- The unexpectedly high water rise in the hole can be explained by the suction effect, high level of the drilling fluid in the hole (and by degassing?)

Summary

Recommendations: 1. Buy a good pressure sensor and install it in the drill!2. Keep fluid level low and density high (instead of other way round)!3. Try to reduce suction effect

Documents

St.Petersburg, 27-28 September 2013 Fr-Ru seminar «Vostok » Results of the new 5G-1N ice core studies related to technology of Lake Vostok unsealing V