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Differing source water inputs, moderated by evaporative enrichment, determine the contrasting δ 18 O CELLULOSE signals in maritime Antarctic moss peat banks
Author(s) -
Royles Jessica,
Sime Louise C.,
Hodgson Dominic A.,
Convey Peter,
Griffiths Howard
Publication year - 2013
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/jgrg.20021
Subject(s) - moss , peat , cellulose , snow , precipitation , environmental chemistry , isotopes of oxygen , stable isotope ratio , surface water , geology , environmental science , hydrology (agriculture) , chemistry , geochemistry , ecology , biology , geomorphology , physics , organic chemistry , quantum mechanics , environmental engineering , geotechnical engineering , meteorology
Oxygen isotope palaeoclimate records, preserved in moss tissue cellulose, are complicated by environmental influences on the relationships between source water inputs and evaporative conditions. We carried out stable isotope analyses of precipitation collected from the maritime Antarctic and cellulose extracted from co‐located Chorisodontium aciphyllum dominated moss peat bank deposits accumulated since 1870 A.D. Analyses of stable oxygen and hydrogen isotope composition of summer precipitation on Signy Island (60.7°S, 45.6°W) established a local meteoric water line (LMWL) similar to both the global MWL and other LMWLs, and almost identical to the HadAM3 isotope‐enabled global circulation model output. The oxygen isotopic composition of cellulose (δ 18 O C ) revealed little temporal variation between four moss peat banks on Signy Island since 1870. However, δ 18 O C followed two patterns with Sites A and D consistently 3‰ enriched relative to δ 18 O C values from Sites B and C. The growing moss surfaces at Sites A and D are likely to have been hydrated by isotopically heavier summer precipitation, whilst at Sites B and C, the moss banks are regularly saturated by the isotopically depleted snow melt streams. Laboratory experiments revealed that evaporative enrichment of C. aciphyllum moss leaf water by 5‰ occurred rapidly following saturation (ecologically equivalent to post‐rainfall or snow melt periods). In addition to the recognized source water‐cellulose fractionation extent of 27 ± 3‰, such a shift would account for the 32‰ difference measured between δ 18 O of Signy Island precipitation and cellulose.