Arctic precipitation is predicted to increase this century. Records of past precipitation seasonality provide baselines for a mechanistic understanding of the dynamics controlling Arctic precipitation. We present an approach to reconstruct Arctic precipitation seasonality using stable hydrogen isotopes (δ2H) of aquatic plant waxes in neighboring lakes with contrasting water residence times and present a case study of this approach in two lakes on western Greenland. Residence time calculations suggest that growing season lake water δ2H in one lake reflects summer precipitation δ2H, while the other reflects amount‐weighted annual precipitation δ2H and evaporative enrichment. Aquatic plant wax δ2H in the “summer lake” is relatively constant throughout the Holocene, perhaps reflecting competing effects of local summer warmth and increased distal moisture transport due to a strengthened latitudinal temperature gradient. In contrast, aquatic plant wax δ2H in the “mean annual lake” is 100‰2H depleted from 6 to 4 ka relative to the beginning and end of the record. Because there are relatively minor changes in summer precipitation δ2H, we interpret the 100‰2H depletion in mean annual precipitation to reflect an increase in winter precipitation amount, likely accompanied by changes in winter precipitation δ2H and decreased evaporative enrichment. Thus, unlike the “summer lake,” the “mean annual lake” records changes in winter precipitation. This dual‐lake approach may be applied to reconstruct past changes in precipitation seasonality at sites with strong precipitation isotope seasonality and minimal lake water evaporative enrichment.
Lacustrine δ2H and δ18O isotope proxies are powerful tools for reconstructing past climate and precipitation changes in the Arctic. However, robust paleoclimate record interpretations depend on site‐specific lake water isotope systematics, which are poorly described in the eastern Canadian Arctic due to insufficient modern lake water isotope data. We use modern lake water isotopes (δ18O and δ2H) collected between 1994–1997 and 2017–2021 from a transect of sites spanning a Québec‐to‐Ellesmere Island gradient to evaluate the effects of inflow seasonality and evaporative enrichment on the δ2H and δ18O composition of lake water. Four lakes near Iqaluit, Nunavut sampled biweekly through three ice‐free seasons reflect mean annual precipitation isotopes with slight evaporative enrichment. In a 23° latitudinal transect of 181 lakes, through‐flowing lake water δ2H and δ18O fall along local meteoric water lines. Despite variability within each region, we observe a latitudinal pattern: southern lakes reflect mean annual precipitation isotopes, whereas northern lakes reflect summer‐biased precipitation isotopes. This pattern suggests that northern lakes are more fully flushed with summer precipitation, and we hypothesize that this occurs because the ratio of runoff to precipitation increases with latitude as vegetation cover decreases. Therefore, proxy records from through‐flowing lakes in this region should reflect precipitation isotopes with minimal influence of evaporation, but vegetation changes in lake catchments across a latitudinal transect and through geologic time may influence the seasonality of lake water isotopic compositions. Thus, we recommend that future lake water isotope proxy records are considered in context with temperature and ecological proxy records.
more » « less- NSF-PAR ID:
- 10445356
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Paleoceanography and Paleoclimatology
- Volume:
- 37
- Issue:
- 5
- ISSN:
- 2572-4517
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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