07 Nov 2023
 | 07 Nov 2023
Status: this preprint is currently under review for the journal CP.

Hydroclimate extreme events detected by a sub-decadal diatom oxygen isotope record of the last 220 years from Lake Khamra, Siberia

Amelie Stieg, Boris K. Biskaborn, Ulrike Herzschuh, Jens Strauss, Luidmila Pestryakova, and Hanno Meyer

Abstract. Northern latitudes have been significantly impacted by recent climate warming, which has increased the probability of experiencing extreme weather events. To comprehensively understand hydroclimate change and reconstruct extreme events such as droughts or floods, appropriate proxy records reaching further back in time are needed beyond meteorological measurements. Here we present a 220-year (2015–1790 CE), gapless stable oxygen isotope record of diatoms (δ18Odiatom) from Lake Khamra (59.99° N, 112.98° E) in Eastern Siberia, an area highly sensitive to climate change and with a demand for palaeohydrological data. From a 210Pb-137Cs-dated sediment short core, this high-resolution proxy record was analysed to reconstruct hydroclimatic extremes on a sub-decadal scale. The interpretation of the δ18Odiatom is supported by meteorological data, modern isotope hydrology, the ratio of planktonic-to-benthic diatom species and geochemical analyses of the same sediment indicative for the conditions in lake and catchment.

A comparison with meteorological data back to 1930 revealed that the δ18Odiatom record of Lake Khamra is primarily influenced by regional precipitation changes rather than air temperature. We identified winter precipitation, which enters the lake as isotopically-depleted snowmelt water, as the key process impacting the diatom isotope variability. We related the overall depletion of δ18Odiatom in recent decades to an observed increase in winter precipitation in the area, likely associated with the global air temperature rise, Arctic sea ice retreat and increased moisture transport inland. Available palaeoclimate proxy records, including a fire reconstruction of the same lake, support the new record as a valuable hydroclimate proxy indicative for precipitation deficits, tendentially excluding solar insolation and air temperature as driving forces even beyond meteorological recordings.

We identified two hydroclimatic extremes in the Lake Khamra δ18Odiatom record, one at the beginning of the 19th century and a second prominent event in the 1950s. Both were interpreted as drought periods, associated with enriched δ18Odiatom values likely caused by reduced winter precipitation and increased evaporation effects, which coincide with phases of reconstructed severe wildfires in the region. Despite the pristine lake area, we observed a triplication of mercury levels in the sediment record since the early 20th century, interpreted as an indication of human air pollution.

Amelie Stieg et al.

Status: open (until 02 Jan 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-85', Anonymous Referee #1, 13 Nov 2023 reply
  • RC2: 'Comment on cp-2023-85', Anson Mackay, 01 Dec 2023 reply

Amelie Stieg et al.

Amelie Stieg et al.


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Short summary
Siberia is impacted by recent climate warming and experiences extreme hydroclimate events. We present a 220 year long sub-decadal stable oxygen isotope record of diatoms from Lake Khamra. Our analysis identifies winter precipitation as the key process impacting the isotope variability, highlighting two extreme dry periods. These two events were found to coincide with significant changes in lake internal conditions and increased wildfire activity in the region.