Storm frequency and magnitude in response to Holocene climate variability, Lake Tutira, North-Eastern New Zealand

Abstract

A mid to late Holocene record of storm events is preserved in the sediments of Lake Tutira, located on the eastern North Island of New Zealand. Previous studies of a 6 m sediment core established a storm chronology for the last 2250 years (Eden, D.N., Page, M.J., 1998. Palaeoclimatic implications of a storm erosion record from late Holocene lake sediments, North Island, New Zealand. Palaeogeogr. Palaeoclimatol. Palaeoecol. 139, 37–58). Here we extend the record, using a 27 m sediment core, to lake formation ∼ 7200 cal. yr ago. Outside the last ∼ 500 yr of human influence, the core records landscape response to natural climate variability and to tectonism/volcanism associated with the active collisional plate boundary setting. Based on sedimentological and biogeochemical analyses, 1400 layers of dominantly terrigenous, storm-derived sediment have been identified. A storm event chronology, supported by twelve tephra and three 14C ages, indicates that storm magnitude and frequency has varied over the last 7200 yr. Twenty-five periods with an increased frequency of large storms occur, typically of decadal to centennial duration. Periods of major storm activity occur at about 500–700, 1100–1250, 1850–2100, 2850–3200, 3600–4000, 4300–4500, 4700–4900, 5700–5900, and 6850–6900 cal. yr BP. Several other local and regional climate proxies record conditions that are consistent with the timing and periodicity of major storms in the Tutira record. A period centred on 2000 yr ago has the highest incidence of storms, with a recurrence of 1 storm/2.9 yr. This is identified as a time of major environmental change by several other records. By comparison, average storm frequency throughout the record is ∼ 1 storm/5 yr, and while this is consistent with modern El Niño-Southern Oscillation (ENSO) periodicity, the record shows no increase in frequency around 4000 years at the time of ENSO intensification. This likely reflects New Zealand's location between tropical and polar latitudes, where climate shifts are driven by the interplay between ENSO, Interdecadal Pacific Oscillation (IPO), and the Southern Annular Mode (SAM). The Lake Tutira record provides support for the growing evidence that climate variability during the Holocene has involved periods of rapid change. Correlation of this detailed storm event and sediment flux record with other geomorphic and sedimentary records in the nearby Waipaoa Source-to-Sink sedimentary system, improves understanding of the timing and rates of climatically-induced landscape change, and its downstream effects.