The influence of climate change on the $$\delta ^{18}\text {O}$$ and $$\delta ^{2}$$H signatures of meteoric waters in Europe and North America

Abstract The isotopic composition of meteoric waters is mainly controlled by temperature and precipitation intensity. Due to the anthropogenic climate change, global temperature and precipitation patterns are changing significantly. This study investigates the influence of ongoing climate change on the $$\delta ^{18}\text {O}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>18</mml:mn> </mml:msup> <mml:mtext>O</mml:mtext> </mml:mrow> </mml:math> and $$\delta ^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> H-signatures of meteoric waters. A spatial interpolation model, using $$\delta ^{18}\text {O}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>18</mml:mn> </mml:msup> <mml:mtext>O</mml:mtext> </mml:mrow> </mml:math> and $$\delta ^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> H-data of the last 60 years for the regions of North America and Europe, reveals that the signatures in these regions become in average more negative over that a time span. At first glance, this observation is counter-intuitive, as the temperature effect predicts a more positive isotope composition with increasing temperature. By comparing the model with other models that simulate, for example, precipitation atmospheric pathways or glacial melting, we identified three processes, that could explain the observed negative trend. First and foremost, we emphasise a change in the $$\delta ^{18}\text {O}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>18</mml:mn> </mml:msup> <mml:mtext>O</mml:mtext> </mml:mrow> </mml:math> -and $$\delta ^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> H-values of the source of the evaporating water. We suggest that the melting of the polar ice masses and the intensification of evaporation at high latitudes cause a reduction in the isotopic value of the generated water vapour. Another mechanism that could contribute to the described depletion in meteoric $$^{18}\text {O}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>18</mml:mn> </mml:mmultiscripts> <mml:mtext>O</mml:mtext> </mml:mrow> </mml:math> and $$^{2}\text {H}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>2</mml:mn> </mml:mmultiscripts> <mml:mtext>H</mml:mtext> </mml:mrow> </mml:math> is the intensification of precipitation events. A third process that probably only plays a minor role on a superregional scale is the general decrease of relative humidity over continents. Overall, we conclude that anthropogenic climate change has a major influence on the $$\delta ^{18}\text {O}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>18</mml:mn> </mml:msup> <mml:mtext>O</mml:mtext> </mml:mrow> </mml:math> and $$\delta ^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>δ</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> H signature of meteoric waters.