1 / 7

Water Isotopes in the hydrology 10/03/18 Dana Mawlood

Water Isotopes in the hydrology 10/03/18 Dana Mawlood . Lecture outline: the hydrological cycle d D and d 18 O variability 3) fractionation processes d 18 O, d D of precipitation 5) modeling d 18 O precip. spectrometer light intake. Water Isotopic Variations.

claudev
Download Presentation

Water Isotopes in the hydrology 10/03/18 Dana Mawlood

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Water Isotopes in the hydrology 10/03/18 Dana Mawlood • Lecture outline: • the hydrological cycle • dD and d18O variability • 3) fractionation processes • d18O, dD of precipitation • 5) modeling d18Oprecip spectrometer light intake

  2. Water Isotopic Variations NOTE: water isotopes are always reported with respect to SMOW Ocean d18O = 0 ± 2‰ dD = 0 ± 16‰ Lake Michigan d18O = -7‰ dD = -54‰ Lake Chad d18O = -20‰ dD = -110‰ Dead Sea d18O = +4.4‰ dD = 0‰ What processes explain these variations?

  3. Temperature effect on the d18O of precipitation holds for both spatial T variability and temporal variability Rozanski, 1993

  4. Surface Water Salinity-d18O relationship - tropics Fairbanks et al., 1997 Slope of d18O-salinity relationship is 0.273 in the deep tropics (<5 N and S), vs. 0.45 elsewhere. Why?

  5. The “Global Meteoric Water Line” – what happens to d18O happens to dD, but with a different a annual mean dD vs. d18O of precipitation But month-to-month variations at a given site fall off this line – “deuterium excess” Craig, 1961 Rozanski, 1993

  6. 1-3km Water Why don’t all waters fall on the GMWL? Or…. why do different “source” waters have different ‘deuterium excess’ values? Fact: water vapor above the ocean is -13‰ in d18O, not the -9.2‰ expected from equilibrium fractionation. Why? • Planetary boundary layer • the layer where exchange occurs • between the surface and the free • atmosphere • evaporation not purely • equilibrium process • what other type of fractionation • is involved? Given the potential for complicated boundary layer physics, it’s a wonder that the GMWL exists at all!

  7. Deuterium excess Humid regions will show smaller departures from GMWL than arid regions. Generally interpreted as a proxy for the “source” of the moisture.

More Related