Reconstructing Arctic Precipitation Seasonality Using Aquatic Leaf Wax δ2H in Lakes With Contrasting Residence Times

• Published in: Paleoceanography and paleoclimatology 2020-07, Vol.35 (7), p.n/a
• Main Authors: Thomas, E. K., Hollister, K. V., Cluett, A. A., Corcoran, M. C.
• Format: Article
• Language: English
• Subjects: Annual precipitation; Aquatic plants; Arctic precipitation; Depletion; Enrichment; Evaporation; Growing season; Holocene; Hydrogen; Hydrogen isotopes; Isotopes; lake; Lakes; Mean annual precipitation; moisture source; Precipitation; precipitation isotope; precipitation seasonality; Records; Residence time; Seasonal variations; Seasonality; Summer; Summer precipitation; Temperature gradients; Waxes; Winter; Winter precipitation
• ISSN: 2572-4517; 2572-4525
• DOI: 10.1029/2020PA003886

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. Key Points Neighboring lakes with contrasting residence times may be used to reconstruct precipitation isotopes from different seasons Western Greenland had wetter winters in the middle Holocene due to increased oceanic heat transport and decreased winter sea ice Holocene summer precipitation isotopes on western Greenland were relatively constant suggesting consistent summer moisture source