Using a Paired Chironomid δ¹⁸O and Aquatic Leaf Wax δ²H Approach to Reconstruct Seasonality on Western Greenland During the Holocene

Abstract

The Arctic hydrological cycle is predicted to intensify as climate warms due to increased poleward moisture transport and greater evaporation in areas previously covered by sea ice (Bintanja & Selten, 2014;Kopec et al., 2016). These mechanisms have different seasonal expressions: reduction of sea ice during fall and winter months causes an increase in local evaporation and thus more fall and winter precipitation, whereas strengthening of the meridional moisture gradient due to increasing temperature causes an increase mainly in summer precipitation (Bintanja & Selten, 2014). Changes in Arctic precipitation seasonality may influence feedbacks between hydroclimate, atmospheric and ocean circulation, and plant communities, and are important for projections of sea level rise and ice sheet dynamics (

Seasonal Variations in Moisture Origin Explain Spatial Contrast in Precipitation Isotope Seasonality on Coastal Western Greenland

“…Indeed, the importance of seasonal moisture source variations on precipitation δ 18 O and δ 2 H has been established for lowand mid-latitude sites (Levin et al, 2009;Li & Garzione, 2017); however, the impact of moisture source on precipitation isotope seasonality has not been as fully examined at high-latitudes. A gap in understanding remains regarding the seasonality of moisture sources and their impact on precipitation isotope seasonality on coastal Greenland, where several lacustrine isotope proxy records document changes in precipitation δ 2 H and δ 18 O through the Holocene (Balascio et al, 2018;Corcoran et al, 2021;Lasher et al, 2017;Thomas et al, 2016Thomas et al, , 2018Thomas et al, , 2020, in some cases deviating from records of local and regional temperature (Axford et al, 2021).…”

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

“…Furthermore, we focus analyses on the mechanisms controlling lake water isotopes during the period when the lake is fully ice‐free, after the influence of lake ice melt and snow melt pooling are well mixed into the lake. This is likely the season when most lake water isotope proxies are produced (e.g., aquatic plant leaf waxes throughout the ice‐free season, insect head capsules late in the ice‐free season (Corcoran et al., 2021)), so is the most important to examine in the context of interpreting lake water isotope proxy records. We incorporate data from the OIPC, existing studies, and other regions in the eastern Canadian Arctic, where appropriate, to overcome these limitations to some degree, but to eliminate them, we would need more detailed precipitation, groundwater, and lake monitoring.…”

“…Lacustrine isotope proxy sensors (e.g., authigenic carbonate, diatom frustules, aquatic plant waxes, midge head capsules, etc. ), which reflect the isotopic composition of the water where they form, are commonly used tools for reconstructing lake water δ 2 H or δ 18 O (hereafter also referred to as lake water isotopes) throughout the Arctic (Chapligin et al., 2012; Corcoran et al., 2021; Thomas et al., 2020; Vachula et al., 2017). In regions with continuous permafrost, lakes are primarily fed by meteoric water (Gibson et al., 2008).…”

Plant wax isotopes in Greenland lakes record widespread CH4 uptake during Holocene warming

“…Expanding on the latter point, we find that d 2 Hmoss values are more 2 H-depleted than wax-inferred d 2 Hprecip values by up to ~160‰, ~170‰, and ~180‰ at TS, WLL, and N3 respectively. A mechanism invoked previously to explain divergent H isotope trends in mid-vs. long-chain plant waxes, including at N3, is changing seasonality of the precipitation stored in lakes, e.g., increased cold-season precipitation 21,22,32 . However, modern seasonal extremes in precipitation d 2 H values at each site are too small to account for this change, only differing by ~80-90‰ at N3 and TS, and ~130‰ in the intensely seasonal climate at WLL (Fig.…”

“…In addition, independent reconstructions of Holocene lake water isotopes at WLL (new data) and N3 (published data) 32 are available, based upon the oxygen isotopic composition of chitinous head capsules of obligate aquatic insect larvae (Chironomidae, δ 18 Ochiron; see Methods). These δ 18 Ochironinferred lake water δ 18 O reconstructions strongly agree with wax-inferred d 2 Hprecip values from long-chain, terrestrial plant waxes at the same lakes (Fig.…”