A high-resolution 1200-year bromine-based paleotemperature record from Maar Lake Chasha (Kamchatka Peninsula)

The North Pacific is a critical component of the global climate system, yet high-resolution quantitative temperature records for the past millennium from this region remain scarce, limiting our understanding of its natural variability and response to forcing factors. This study presents an annually resolved paleotemperature reconstruction for the Kamchatka Peninsula spanning the last 1200 years, based on a calibrated bromine (Br) proxy derived from maar lake sediments.

Synchrotron radiation X-ray fluorescence (SR-XRF) has been used for nondestructive in situ analysis of elements on a precisely dated sediment core from Lake Chasha. Br in lacustrine systems is strongly associated with organic matter through covalent C-Br bonds, and its sedimentary concentration is fundamentally regulated by temperature-dependent primary productivity and terrestrial organic matter flux in this cold region. For the modern period (1989-2020), the Br record shows a strong and statistically significant positive correlation (r=0.72, p<0.001) with instrumental summer air temperature from a nearby meteorological station, validating its use as a quantitative paleothermometer.

The resulting Br-derived temperature record robustly captures the major climatic epochs of the Common Era: the Dark Ages Cold Period (DACP, ~5th–8th centuries), the Medieval Climate Anomaly (MCA, ~9th–13th centuries), and the Little Ice Age (LIA, ~14th–19th centuries). The 20th-century warming signal is unprecedented in amplitude over the entire 1200-year period. Spectral analysis reveals significant periodicities at ~88,10-11 years and 3-4 years. Visual comparison and coherence analysis indicate that multi-decadal to centennial-scale variability in the record is modulated by both internal climate dynamics, showing an anti-correlation with Pacific Decadal Oscillation (PDO) phases, and external solar forcing, with notable correspondence to major solar minima (e.g., Maunder Minimum).

Our result provides a high-resolution benchmark for the North Pacific, significantly improving our capacity to characterize natural climate variability, evaluate climate models, and decipher the regional interplay between internal ocean-atmosphere oscillations.