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

Late Pleistocene - Holocene climate variations over 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

Groundwater as a climate proxy Precipitation (P) P Soil Soil Humidity (Recharge rate) Temperature Re Re Groundwater Groundwater Climate  Recharge conditions

Noble gases (He, Ne, Ar, Kr, Xe) 1. Reconstruct recharge temperatures: NGT-noble gas recharge temperature Solubility W E L Quasi- L Temperature saturated zone Water table Aquifer fluctuations Recharge-Precipit. 2. Reconstruct humidity conditions: Δ Ne- Excess air Humidity Inverse modeling of the observed noble gas Input of meltwater concentrations is used to interpret the data in terms of recharge temperature and excess air.

Stable isotopes ( 2 H and 18 O ) 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

EUROPE: last glacial maximum a) A large number of small Scandinavian ice sheet glaciers developed in the Krkonose Mountains Bohemian Cretaceus b) The basin was covered by Basin discontinuos permafrost Alpine ice field A key region for understanding late Pleistocene climate and glacial development 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

Cenomanian and Turonian sands aquifers, Czech Republic Uranium Flow direction mining N Liberec S VP7502 VP7506 Turnov VP7500 VP7523 Duba syncline VP7515 VP7512 Mlada Boleslav VP7524 VP7517 Zivonin syncline Vltava river VP7520 VP7519 Karany B - - - - - - Important faults Prague 1. Noble gases: He, Ne, Ar, Kr, Xe Wells in the Cenomanian sandstone Stable isotopes: 2 H, 18 O, 13 C Wells in the Turonian sandstone 2. GW dating tracers: 3 H/ 3 He, 85 Kr, 39 Ar, 14 C 3. 4. Hydrochemistry, etc.

14 C age vs distance from recharge 14 C activity vs distance from recharge 60 30000 An average ground water flow velocity within the aquifer of 50 25000 2.3 m/y is estimated. 14 C in DIC (pmC) 40 Mixture 20000 Input of 14 C age (yrs.) mantle CO 2 30 15000 20 10000 10 5000 0 0 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 Distance from recharge (km) Distance from recharge (km) Piston-Flow Model Initial 14 C ages were corrected with the 39 Ar ages Spreadsheet, NETPATH and PHREEQC calculations were performed to account for chemical reactions and isotope exchange.

Concentration of 4 He vs 14 C age Vertical flux of helium from deeper formations -5 1.5x10 Piston-Flow Model 3 STP/g water) 4 He] = 4.8E-10 * (Age) + 1.6E-7 [ R = 0.99 -5 1.0x10 4 He] (cm -6 5.0x10 [ Aquifer accum. rate (calculated) 3 STPHe/cm 3 water/yr 2E-11 cm 0 5000 10000 15000 20000 25000 30000 14 C age (yr) The 14 C model ages are further confirmed by the linear correlation with the concentrations of radiogenic 4 He .

Age distribution along the flow direction Flow velocity: 2.3 m/yr Last ice age

Low resolution stable isotope ( 18 O and 2 H) records -9.0 -63 Oxygen-18 LGM 1. Depleted δ 18 O and δ 2 H Deuterium -9.5 -67 during the LGM confirm low air temperatures -10.0 δ 18 O (‰) δ 2 H (‰) -71 -10.5 2. Depletion consistent with -75 -11.0 isotope shift in the ocean surface during the LGM -79 -11.5 -12.0 -83 0 10000 20000 30000 14 C age (yrs) Stute and Schlosser, 2001.

Low resolution noble gas temperature (NGT) record 10 LGM Late Holocene 1. Low NGT of just above the (Modern) 8 freezing point during the LGM Pre-industrial Holocene 6 2. Glacial/interglacial warming NGT ( o C) of 5 to 7 o C Δ T~ 7 0 C Δ T~ 5 0 C 4 2 LGM NGT = 0.8 o C 0 10 100 1000 10000 14 C age (yrs) The closed-system equilibration (CE) model was used to describe the NGT and excess air component (Aeschbach-Hertig et al., 2000).

Glacial/interglacial shifts in Europe, groundwater Ice covered/permafrost region -> No Infiltration during LGM, etc. Coastal areas: large variations of air Temp. 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

Excess air in groundwater (expressed as Δ Ne) a) meltwater input? 140 - Pure meltwater: Δ Ne > 500 % - Stable isotopes: not highly High excess air in 120 depleted GW during the LGM - Recharge of large amounts of 100 another water component 80 b) Increased water table ΔNe (%) fluctuations and hydraulic loading due to frequent 60 intense rain events? 40 Typical in groundwater: LGM c) Abrupt change in recharge 10-50 % 20 dynamics? - progression and retreat of ice covers and permafrost 0 10 100 1000 10000 14 C age (yrs) 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

Deuterium excess in groundwater Decrease of deuterium excess linked Temporal decrease of deuterium excess from to an increase of air temperatures pre-industrial Holocene to present days 14 14 12 Glacial Deuterium excess ( ‰ ) 12 Present days 10 d-excess= 8.6 d excess (‰) in precipitation 10 8 6 8 Modern 4 d = -0.33 (NGT) + 11.12 6 2 MA - Cracow, Poland R² = 0.21 CA + TA - Czech Republic 0 4 0 2 4 6 8 10 0 20 40 60 80 100 NGT ( o C) 14 C activity (pmC) MA – Oligocene Mazonian basin (Poland) (Zuber et al., 2000) Froehlich et al., 2002

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

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