Oxygen stable isotope ratios from British oak tree-rings provide a strong and consistent record of past changes in summer rainfall

Abstract

United Kingdom (UK) summers dominated by anti-cyclonic circulation patterns are characterised by clear skies, warm temperatures, low precipitation totals, low air humidity and more enriched oxygen isotope ratios ( 18 O) in precipitation. Such conditions usually result in relatively more positive (enriched) oxygen isotope ratios in tree leaf sugars and ultimately in the tree-ring cellulose formed in that year, the converse being true in cooler, wet summers dominated by westerly air flow and cyclonic conditions. There should therefore be a strong link between tree-ring  18 O and the amount of summer precipitation. Stable oxygen isotope ratios from the latewood cellulose of 40 oak trees sampled at eight locations across Great Britain produce a mean  18 O chronology that correlates strongly and significantly with summer indices of total shear vorticity, surface air pressure, and the amount of summer precipitation across the England and Wales region of the United Kingdom. The isotope-based rainfall signal is stronger and much more stable over time than reconstructions based upon oak ring widths. Using recently developed methods that are precise, efficient and highly costeffective it is possible to measure both carbon ( 13 C) and oxygen ( 18 O) isotope ratios simultaneously from the same tree-ring cellulose. In our study region, these two measurements from multiple trees can be used to reconstruct summer temperature ( 13 C) and summer precipitation ( 18 O) with sufficient independence to allow the evolution of these climate parameters to be reconstructed with high levels of confidence. The existence of long, well-replicated oak tree-ring chronologies across the British Isles mean that it should now be possible to reconstruct both summer temperature and precipitation over many centuries and potentially millennia.

Absence of Age‐Related Trends in Stable Oxygen Isotope Ratios From Oak Tree Rings

“…Trends in the isotope data from the modern trees are compared with those in the England and Wales precipitation record for May to August (Alexander & Jones, 2001;Young et al, 2015). Trends in the preindustrial series are compared with relevant sections of a long stable oxygen isotope "master chronology" based on pooled latewood cellulose from 10 separate trees (Loader et al, 2019).…”

“…Given the cost involved, suitable data sets are sparse and are also heavily biased toward conifers growing at high latitudes and altitudes. No similarly detailed studies have been conducted on European oaks, but the limited evidence that is available suggests that there are no long age trends in oak tree ring δ 18 O (Duffy et al, 2017;Li et al, 2015;Young et al, 2015). However, in perhaps the most comprehensive single study, Young et al (2011) identified no such effect in tree line conifers.…”

Seasonal temperature and precipitation recorded in the intra-annual oxygen isotope pattern of meteoric water and tree-ring cellulose

“…One fate for meteoric water is uptake by plant roots and incorporation into plant tissues; in fact, meteoric water exerts fundamental control on the oxygen isotope signature of plant tissues (Deniro and Epstein, 1979). Because trees are long-lived and tree fossils are abundant in the fossil record, workers have long sought to gain physiological (Gessler et al, 2009;Offermann et al, 2011) or environmental information from the oxygen isotope composition of both modern (Brienen et al, 2012;Knorre et al, 2010;Loader et al, 2010Loader et al, , 2007McCarroll and Loader, 2004;Poussart et al, 2004;Rinne et al, 2013;Saurer et al, 2008;Treydte et al, 2006;Young et al, 2015) and ancient wood (Jahren and Sternberg, 2002, 2008Richter et al, 2008a;Wolfe et al, 2012). Cellulose has been the substrate of choice because it is resistant to degradation (e.g., Griffith et al, 2008;Jahren and Sternberg, 2002) and can be extracted from heterogeneous lignin complexes (Green, 1963 (Csank et al, 2013;Richter et al, 2008b;Saurer et al, 1997;Sternberg et al, 2007;Waterhouse et al, 2002;Yakir and DeNiro, 1990).…”

French summer droughts since 1326 CE: a reconstruction based on tree ring cellulose <i>δ</i><sup>18</sup>O

“…Loader et al, 2008;Saurer et al, 2008;Young et al, 2012). They can help extend climate reconstructions into regions which are not yet well covered , and also provide information about precipitation amount (Rinne et al, 2013;Young et al, 2015). Recent studies have revealed the sensitivity of cellulose δ 18 O to the combined effects of temperature and humidity, and therefore of drought (Raffalli-Delerce et al, 2004;MassonDelmotte et al, 2005;Etien et al, 2008Etien et al, , 2009Labuhn et al, 2014).…”