Reassessing the role of temperature in precipitation oxygen isotopes across the eastern and central United States through weekly precipitation‐day data

• Published in: Water resources research 2017-09, Vol.53 (9), p.7644-7661
• Main Authors: Akers, Pete D., Welker, Jeffrey M., Brook, George A.
• Format: Article
• Language: English
• Subjects: Air temperature; Annual temperature range; Annual temperatures; Atmospheric precipitations; Cyclones; Environmental control; Environmental factors; Extratropical cyclones; Geography; hydroclimate; Interactions; isoscape; Isotope ratios; Isotopes; Oxygen; oxygen isotope; Oxygen isotope ratio; Oxygen isotopes; Precipitation; precipitation isotope; Rain; Ratios; Temperature; Temperature data; temperature effect; Temperature effects; Temperature rise; Trends; Variability; Weather; Weekly; δ18O
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1002/2017WR020569

Air temperature is correlated with precipitation oxygen isotope (δ18Oprcp) variability for much of the eastern and central United States, but the nature of this δ18Oprcp‐temperature relationship is largely based on data coarsely aggregated at a monthly resolution. We constructed a database of 6177 weeks of isotope and precipitation‐day air temperature data from 25 sites to determine how more precise data change our understanding of this classic relationship. Because the δ18Oprcp‐temperature relationship is not perfectly linear, trends in the regression residuals suggest the influence of additional environmental factors such as moisture recycling and extratropical cyclone interactions. Additionally, the temporal relationships between δ18Oprcp and temperature observed in the weekly data at individual sites can explain broader spatial patterns observed across the study region. For 20 of 25 sites, the δ18Oprcp‐temperature relationship slope is higher for colder precipitation than for warmer precipitation. Accordingly, northern and western sites with relatively more cold precipitation events have steeper overall relationships with higher slope values than southeastern sites that have more warm precipitation events. Although the magnitude of δ18Oprcp variability increases to the north and west, the fraction of δ18Oprcp variability explained by temperature increases due to wider annual temperature ranges, producing stronger relationships in these regions. When our δ18Oprcp‐temperature data are grouped by month, we observe significant variations in the relationship from month to month. This argues against a principal causative role for temperature and suggests the existence of an alternative environmental control on δ18Oprcp values that simply covaries seasonally with temperature. Plain Language Summary In the eastern and central United States, the oxygen isotope ratio of rain or snow is linked to the air temperature while it rains or snows: warmer temperatures have higher isotope ratios and colder temperatures have lower isotope ratios. If we have a record of these isotope ratios dating back into the past, we can estimate how the weather has changed for a given location over time. However, we need a solid understanding of how isotope ratios are controlled in the present day in order to make any estimations about the past. Previous research studying the present day effect of air temperature on isotope ratios have used databases that average an entire month of weat