Abstract
Abstract. Water isotopes in precipitation have played a key role in the reconstruction of past climate on millennial timescales and longer. However, for midlatitude regions like East Asia with complex terrain, the reliability behind the basic assumptions of the temperature effect and amount effect is based on modern observational data and still remains unclear for past climate. In the present work, we reexamine the two basic effects on seasonal, interannual, and millennial timescales in a set of time slice experiments for the period 22–0 ka using an isotope-enabled atmospheric general circulation model (AGCM). Our study confirms the robustness of the temperature and amount effects on the seasonal cycle over China in the present climatic conditions, with the temperature effect dominating in northern China and the amount effect dominating in the far south of China but no distinct effect in the transition region of central China. However, our analysis shows that neither temperature nor amount effect is significantly dominant over China on millennial and interannual timescales, which is a challenge to those classic assumptions in past climate reconstruction. Our work helps shed light on the interpretation of the proxy record of δ18O from a modeling point of view.
Highlights
Stable water isotopes have been recognized as key tracers for tracking temperature footprint and moisture sources in air masses (e.g., Dansgaard, 1964; Grootes et al, 1993; Cuffey et al, 1995; Salamatin et al, 1998; Noone, 2008; Sturm et al, 2010)
Based on the present relationship between δ18O records and temperature/precipitation, earlier observational studies suggest that the δ18O–temperature relationship at high latitudes tends to be associated with the “local temperature effect”, a positive correlation between δ18O in precipitation and the temperature of ambient air, whereas the δ18O–precipitation relationship in the tropics and low latitudes tends to be associated with the “amount” effect, a negative correlation between δ18O in precipitation and the accumulated total rainfall on local and upstream regions (Dansgaard, 1964)
We have examined the temperature and amount effects on seasonal, interannual, and millennial timescales in East Asia in an isotope-enabled atmospheric general circulation models (GCMs)
Summary
Stable water isotopes have been recognized as key tracers for tracking temperature footprint and moisture sources in air masses (e.g., Dansgaard, 1964; Grootes et al, 1993; Cuffey et al, 1995; Salamatin et al, 1998; Noone, 2008; Sturm et al, 2010). 2008; Cheng et al, 2009; Chu et al, 2012), ice cores (Davis and Thompson, 2004; Davis et al, 2005; Thompson et al, 2000, 2006), tree rings (Feng et al, 1999; Grießinger et al, 2011), and lake sediments (Morrill et al, 2003, 2006; Zhang et al, 2011) found in the monsoon region, especially in East Asia These studies tend to suggest that these isotope records reflect the East Asia summer monsoon (EASM) rainfall through the amount effect. One basic and key question is whether the present-day relationship between δ18O and temperature/precipitation in East Asia for, say, a seasonal cycle, is valid for interpreting past climate on millennial timescales or longer.
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