groundwater data J.A. Corcho Alvarado Institute of Radiation - - PowerPoint PPT Presentation

Late Pleistocene - Holocene climate variations

• ver central Europe reconstructed from

groundwater data

J.A. Corcho Alvarado Institute of Radiation Physics, Univ. Hospital and Univ. of Lausanne, Switzerland

• R. Purtschert, M. Leuenberger

Climate and Environmental Physics, Univ. of Bern, .Switzerland

• R. Kipfer
• Dep. of Water Resources and Drinking Water, EAWAG, Switzerland

Institute of Geochemistry and Petrology, ETH Zurich, Switzerland

University of Bern

Outline

• 1. Reconstruction of past climate conditions from

groundwater data: a short introduction

• 2. Groundwater ages in investigated aquifers of the

Bohemian Cretaceous Basin

• 3. Reconstruction of past climate conditions
• 4. Conclusions

Climate  Recharge conditions

Precipitation (P)

P Re Groundwater

Soil Humidity (Recharge rate)

Groundwater

Soil Temperature

Re

Groundwater as a climate proxy

Water table fluctuations Recharge-Precipit. Humidity

Solubility Temperature

Aquifer

W E L L

Quasi- saturated zone

Noble gases (He, Ne, Ar, Kr, Xe)

• 1. Reconstruct recharge temperatures:

NGT-noble gas recharge temperature

• 2. Reconstruct humidity conditions:

ΔNe- Excess air

Input of meltwater

Inverse modeling of the observed noble gas concentrations is used to interpret the data in terms of recharge temperature and excess air.

Stable isotopes (2H and 18O ) as paleoclimate proxies – Reconstruct paleotemperature (T effect) – Reconstruct paleoprecipitation (amount effect)

Stute and Schlosser, 2001. Atmospheric noble gases, in Environmental tracers in subsurface hydrogeology, Cook and Herczeg (ed). Kluwer Academic Publishers

Low resolution paleotemperature record

Recharge area Discharge area

Aquifer

Alpine ice field Scandinavian ice sheet

Bohemian Cretaceus Basin

EUROPE: last glacial maximum

Ice age Earth at glacial maximum. Based on: "Ice age terrestrial carbon changes revisited" by Thomas J. Crowley (Global Biogeochemical Cycles, Vol. 9, 1995, pp. 377-389

A key region for understanding late Pleistocene climate and glacial development

a) A large number of small glaciers developed in the Krkonose Mountains b) The basin was covered by discontinuos permafrost

Cenomanian and Turonian sands aquifers, Czech Republic

Vltava river

Prague

Mlada Boleslav

Turnov Liberec

Zivonin syncline Duba syncline

VP7502 VP7506 VP7500 VP7515 VP7517 VP7519

Karany B

VP7523 VP7512 VP7524 VP7520

N

S

• - - - - - Important faults

Wells in the Cenomanian sandstone Wells in the Turonian sandstone

Flow direction

Uranium mining

1. Noble gases: He, Ne, Ar, Kr, Xe 2. Stable isotopes: 2H, 18O, 13C 3. GW dating tracers: 3H/3He, 85Kr, 39Ar, 14C 4. Hydrochemistry, etc.

10 20 30 40 50 60 70 5000 10000 15000 20000 25000 30000

14C age (yrs.)

Distance from recharge (km)

Piston-Flow Model

An average ground water flow velocity within the aquifer of 2.3 m/y is estimated.

10 20 30 40 50 60 70 10 20 30 40 50 60

Mixture Input of mantle CO2

14C in DIC (pmC)

Distance from recharge (km) 14C activity vs distance from recharge 14C age vs distance from recharge

Initial 14C ages were corrected with the 39Ar ages Spreadsheet, NETPATH and PHREEQC calculations were performed to account for chemical reactions and isotope exchange.

5000 10000 15000 20000 25000 30000 5.0x10

• 6

1.0x10

• 5

1.5x10

• 5

Aquifer accum. rate (calculated) 2E-11 cm

3STPHe/cm 3water/yr

[

4He] = 4.8E-10 * (Age) + 1.6E-7

R = 0.99

[

4He] (cm 3 STP/g water) 14C age (yr)

The 14C model ages are further confirmed by the linear correlation with the concentrations of radiogenic 4He .

Vertical flux of helium from deeper formations

Piston-Flow Model

Concentration of 4He vs 14C age

Age distribution along the flow direction

Last ice age Flow velocity: 2.3 m/yr

• 83
• 79
• 75
• 71
• 67
• 63
• 12.0
• 11.5
• 11.0
• 10.5
• 10.0
• 9.5
• 9.0

10000 20000 30000

δ2H (‰) δ18O (‰)

14C age (yrs)

Oxygen-18 Deuterium

LGM

Low resolution stable isotope (18O and 2H) records

• 1. Depleted δ18O and δ2H

during the LGM confirm low air temperatures

• 2. Depletion consistent with

isotope shift in the ocean surface during the LGM

Stute and Schlosser, 2001.

2 4 6 8 10 10 100 1000 10000

NGT (oC)

14C age (yrs)

Low resolution noble gas temperature (NGT) record

LGM

LGM NGT = 0.8 oC

ΔT~ 5 0C

Pre-industrial Holocene Late Holocene (Modern)

ΔT~ 7 0C

• 1. Low NGT of just above the

freezing point during the LGM

• 2. Glacial/interglacial warming
• f 5 to 7 oC

The closed-system equilibration (CE) model was used to describe the NGT and excess air component (Aeschbach-Hertig et al., 2000).

Ice covered/permafrost region -> No Infiltration during LGM, etc. Coastal areas: large variations of air Temp.

Glacial/interglacial shifts in Europe, groundwater

Bath et al., 1979; Rudolph et al., 1984; Stute and Deák, 1989; Beyerle et al., 1998; Huneau et al., 2002; Zuber et al., 2000; Vaikmäe, 2001; Zuber et al., 2004; Blaser et al., 2010; Varsanyi et al., 2011

20 40 60 80 100 120 140 10 100 1000 10000

ΔNe (%)

14C age (yrs)

Excess air in groundwater (expressed as ΔNe)

LGM

High excess air in GW during the LGM a) meltwater input?

• Pure meltwater: ΔNe > 500 %
• Stable isotopes: not highly

depleted

• Recharge of large amounts of

another water component

Typical in groundwater:

10-50 % b) Increased water table fluctuations and hydraulic loading due to frequent intense rain events? During the LGM: a) The climate was dry, with air temperatures near freezing point b) A large number of small glaciers developed in the Krkonose Mountains (Recharge area) c) The Bohemian basin was covered by discontinuos permafrost c) Abrupt change in recharge dynamics?

• progression and retreat of ice

covers and permafrost

4 6 8 10 12 14 20 40 60 80 100

Deuterium excess ( ‰)

14C activity (pmC)

MA - Cracow, Poland CA + TA - Czech Republic

Modern Glacial

Present days d-excess= 8.6 in precipitation

Deuterium excess in groundwater

Temporal decrease of deuterium excess from pre-industrial Holocene to present days

d = -0.33 (NGT) + 11.12 R² = 0.21

2 4 6 8 10 12 14 2 4 6 8 10

d excess (‰) NGT (oC)

Decrease of deuterium excess linked to an increase of air temperatures

Froehlich et al., 2002

MA – Oligocene Mazonian basin (Poland) (Zuber et al., 2000)

Conclusions

• 1. The low resolution NGT-record indicated a glacial cooling of at least 5 –

7 °C for the Bohemian Cretaceous Basin region, consistent with other studies in Europe.

• 2. A high excess air (ΔNe) in groundwater at the end of the Pleistocene is

possibly related to changes in the recharge dynamics of groundwater by the progression and retreat of ice covers and permafrost

• 3. A temporal decrease of deuterium excess in groundwater from pre-

industrial Holocene to present days is linked to an increase of the air temperatures

Thank you for your attention!!!