Modern Eastern Canadian Arctic Lake Water Isotopes Exhibit Latitudinal Patterns in Inflow Seasonality and Minimal Evaporative Enrichment

Abstract

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.

Seasonal precipitation variability on Svalbard inferred from Holocene sedimentary leaf wax δ2H

“…This suggests that most of the water in the lake is flushed by water with isotope values close to summer precipitation during the growing season, perhaps due to large inputs from active layer thaw (Gorbey et al . 2022) or that snow‐melt input to this lake is minimal, due to ‘snow‐melt bypass’, i.e. snow melting off the landscape before the lake becomes ice‐free (MacDonald et al .…”

“…2022) and ice‐free season lake water δ 2 H and summer precipitation δ 2 H values (Gorbey et al . 2022) from Baffin Island, Canada. We consider these calibration data to be the most representative for Svalbard since the sites have fairly similar climate (low‐lying/coastal, cold, high‐Arctic) and vegetation (terrestrial: graminoids, dwarf shrubs, moss mats; aquatic: dominated by submerged mosses).…”

Early Holocene Laurentide Ice Sheet Retreat Influenced Summer Atmospheric Circulation in Baffin Bay

“…We interpret Lake CF8 brGDGT‐inferred temperature to reflect regional summer air temperature, as is common in Arctic lakes (Text S3.1 in Supporting Information ) (Allegrucci et al., 2012; Buizert et al., 2018; Chen et al., 2022; Delettre, 1988; Denton et al., 2005; de Wet et al., 2016; Francis et al., 2006; Green & Sánchez, 2006; Halamka et al., 2023; Keisling et al., 2017; Kusch et al., 2019; Lindberg et al., 2022; Livingstone & Lotter, 1998; MacIntyre et al., 2009; Raberg et al., 2021; Shanahan et al., 2013; Thomas et al., 2018; Wu et al., 2021; Zhang et al., 2016; Zhao et al., 2021). We interpret δ 2 H of the C 28 n ‐alkanoic acid from Lake CF8 to reflect summer lake water δ 2 H values, which in turn reflect summer precipitation δ 2 H values (Texts S3.2 and S3.3 in Supporting Information ) (Faber et al., 2017; Gao et al., 2011; Gorbey et al., 2022; Johnsen et al., 2001; Paterson et al., 1977; Rach et al., 2014; Sachse et al., 2012; Thomas et al., 2020; van Bree et al., 2018). The difference between δ 2 H of terrestrial and aquatic waxes, ɛ terrestrial‐aquatic , reflects changes in the amount of snow melt contributing to soil water and/or changes in evaporation from soil or leaf water (Text S3.3.2 in Supporting Information ).…”

“…Lake CF8 water δ 2 H values match summer precipitation, with no evaporative enrichment (Text S3.2 and Figure S2 in Supporting Information S1) (Bowen, 2016;Bowen et al, 2005;Chiasson-Poirier et al, 2020;Gibson & Edwards, 2002;Gorbey et al, 2022;IAEA/WMO, 2011;Jonsson et al, 2009;Zhao et al, 2022). Hereafter, we primarily discuss δ 2 H C28 , which we convert to summer precipitation δ 2 H using an apparent fractionation factor derived from aquatic plants in Qaupat Lake, southern Baffin Island (Text S1.6 in Supporting Information S1) (Gorbey et al, 2022;Guo et al, 2013;Hollister et al, 2022;McFarlin et al, 2019). (Liu et al, 2009).…”

“…We interpret the C 28 n-alkanoic acid in Lake CF8 as predominantly aquatic and the C 22 n-alkanoic acid as at least partially terrestrial, based on similar chain-length distributions with submerged aquatic mosses, the most abundant plant in the catchment, and different trends in δ 2 H values for different chain lengths (Text S3.3 and Figure S8 in Supporting Information S1). Lake CF8 water δ 2 H values match summer precipitation, with no evaporative enrichment (Text S3.2 and Figure S2 in Supporting Information S1) (Bowen, 2016;Bowen et al, 2005;Chiasson-Poirier et al, 2020;Gibson & Edwards, 2002;Gorbey et al, 2022;IAEA/WMO, 2011;Jonsson et al, 2009;Zhao et al, 2022). Hereafter, we primarily discuss δ 2 H C28 , which we convert to summer precipitation δ 2 H using an apparent fractionation factor derived from aquatic plants in Qaupat Lake, southern Baffin Island (Text S1.6 in Supporting Information S1) (Gorbey et al, 2022;Guo et al, 2013;Hollister et al, 2022;McFarlin et al, 2019).…”