Summer sea-ice variability on the Antarctic margin during the last glacial period reconstructed from snow petrel (<i>Pagodroma nivea</i>) stomach-oil deposits

Abstract

Abstract. Antarctic sea ice is a critical component of the climate system affecting a range of physical and biogeochemical feedbacks and supporting unique ecosystems. During the last glacial stage, Antarctic sea ice was more extensive than today, but uncertainties in geological (marine sediments), glaciological (ice core), and climate model reconstructions of past sea-ice extent continue to limit our understanding of its role in the Earth system. Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea) preserved at nesting sites in Dronning Maud Land, Antarctica. We show that by combining information from fatty acid distributions and their stable carbon isotope ratios with measurements of bulk carbon and nitrogen stable isotopes and trace metal data, it is possible to reconstruct changing snow petrel diet within Marine Isotope Stage 2 (ca. 24.3–30.3 cal kyr BP). We show that, as today, a mixed diet of krill and fish characterizes much of the record. However, between 27.4 and 28.7 cal kyr BP signals of krill almost disappear. By linking dietary signals in the stomach-oil deposits to modern feeding habits and foraging ranges, we infer the use by snow petrels of open-water habitats (“polynyas”) in the sea ice during our interval of study. The periods when consumption of krill was reduced are interpreted to correspond to the opening of polynyas over the continental shelf, which became the preferred foraging habitat. Our results show that extensive, thick, and multiyear sea ice was not always present close to the continent during the last glacial stage and highlight the potential of stomach-oil deposits as a palaeoenvironmental archive of Southern Ocean conditions.

Marine Radiocarbon Calibration in Polar Regions: A Simple Approximate Approach using Marine20

“…An alternative need for polar calibration occurs when creating age-depth models for sediment cores based upon multiple 14 C determinations. Such models are typically used to estimate calendar ages at particular core depths, perhaps to investigate the timings of changes in other proxies recorded within the core (e.g., McClymont et al, 2022;Taylor et al, 2014).…”

“…Several proxies have been proposed. These include micropaleontological transfer functions based on diatoms (e.g., Gersonde et al, 2005) and dinocysts (de Vernal et al, 2001); molecular abundance of a particular hydrocarbon (IP25) synthesized by diatoms living at the bottom of sea ice (Belt & Müller, 2013); and stomach-oil deposits from sea-petrels (McClymont et al, 2022;Thatje et al, 2008). Several authors have used these proxies to show systematic changes of sea-ice linked to abrupt climate changes (Hoff et al, 2016;Méheust et al, 2018;Stein et al, 2017) To investigate whether such a sliding, sea-ice proxy-informed, Δ𝑅(𝜃) correction improves calendar dating would require suitable independent testing: either by comparing the resultant core chronology against absolute chronologies; or with downcore evidence of local MRA changes (e.g., using tephra).…”

Emerging biological archives can reveal ecological and climatic change in Antarctica

“…Sea ice (Berg, Melles, et al, 2019 ; Cleary et al, 2021 ; de Bruyn et al, 2014 ; McClymont et al, 2022 )…”

“…Analyses of dietary and/or stable isotope composition of animal remains reflects the environment in which the animals were feeding (e.g., in polynyas versus loose pack ice), which sheds light on sea ice conditions, and more broadly, can inform us of species responses to environmental change (Berg, White, Hermichen, et al, 2019 ; McClymont et al, 2022 ) (Tables 1 and 2 ). Several studies indicate that episodic occupation of sites by Adélie penguins on the Antarctic continent (e.g., Xu et al, 2020 ) reflects periods of enhanced marine productivity and greater nesting site availability during past warmer climates, in particular the penguin ‘optimum’ (~2–5 million years ago, Ma) (see Younger et al ( 2016 ) and references within).…”

Reconstructing the Paleo‐Ecological Diet of Snow Petrels (Pagodroma nivea) From Modern Samples and Fossil Deposits: Implications for Southern Ocean Paleoenvironmental Reconstructions

“…As a defense snow petrels spit the oil at nest robbers (mainly skuas) and it accumulates in the surroundings and entrances of the nest cavities over time. These deposits (also termed “Antarctic mumiyo”) can reach several decimeters in thickness, contain consistent stratigraphies and can be well‐dated by radiocarbon analysis (e.g., Berg, Melles, et al., 2019; Hiller et al., 1995; McClymont et al., 2022; Wand & Hermichen, 2005). While the regional distribution and age of the deposits provides information on past distribution of snow petrel breeding sites (e.g., Berg, White, et al., 2019; Thor & Low, 2011; Verkulich & Hiller, 1994), the isotopic and lipid composition of the stomach oil deposits reflect changes in (paleo)diet, which in turn is expected to relate to summer sea‐ice variability in coastal regions (Ainley et al., 2006; McClymont et al., 2022).…”