Holocene atmospheric circulation in the central North Pacific: A new terrestrial diatom and δ18O dataset from the Aleutian Islands

Abstract

a b s t r a c tThe North Pacific is a zone of cyclogenesis that modulates synoptic-scale atmospheric circulation, yet there is a paucity of instrumental and paleoclimate data to fully constrain its long-term state and variability. We present the first Holocene oxygen isotope record (d 18 O diatom ) from the Aleutian Islands, using siliceous diatoms preserved in Heart Lake on Adak Island (51.85 N, 176.69 W). This study builds on previous work demonstrating that Heart Lake sedimentary d 18 O diatom values record the d 18 O signal of precipitation, and correlate significantly with atmospheric circulation indices over the past century. We apply this empirical relationship to interpret a new 9.6 ka d 18 O diatom record from the same lake, supported by diatom assemblage analysis. Our results demonstrate distinct shifts in the prevailing trajectory of storm systems that drove spatially heterogeneous patterns of moisture delivery and climate across the region. During the early-mid Holocene, a warmer/wetter climate prevailed due to a predominantly westerly Aleutian Low that enhanced advection of warm 18 O-enriched Pacific moisture to Adak, and culminated in a d 18 O diatom maxima (33.3‰) at 7.6 ka during the Holocene Thermal Maximum. After 4.5 ka, relatively lower d 18 O diatom indicates cooler/drier conditions associated with enhanced northerly circulation that persisted into the 21st century. Our analysis is consistent with surface climate conditions inferred from a suite of terrestrial and marine climate-proxy records. This new Holocene dataset bridges the gap in an expanding regional network of paleoisotope studies, and provides a fresh assessment of the complex spatial patterns of Holocene climate across Beringia and the atmospheric forces driving them.

Spatial distribution of environmental indicators in surface sediments of Lake Bolshoe Toko, Yakutia, Russia

“…Similar neutral pH values measured in water samples from the central basin and the lagoon (Table 1) questions pH as a main driving factor of the Eunotia peak in the lagoon. However, Barinova et al (2011) suggest a 5.0-5.8 pH range for the identified Eunotia species, which rather indicates that the pH values obtained during April in 2013 are not representative for the annual average and the specific catchment of the lagoon, which likely will differ from this point measurement. The ice break-up during spring and transport of water from the catchment restricted to the lagoon likely leads to milieu differences in the lagoon relative to the main basin.…”

“…Generally, planktonic and benthic diatom species have strategies to survive in ice-covered lakes by growing in benthic mode, forming resting spores, or attaching to the ice-cover substrate (D'souza, 2012). Hence, the duration and presence of ice cover can significantly impact both changes in assemblage composition and spatial distribution, particularly including the ratio of planktonic to benthic diatoms (Wang et al, 2012a;Bailey et al, 2018).…”

“…6b). For example, existing studies have used lacustrine δ 18 O diatom to reconstruct past changes in precipitation amount and seasonality, the precipitation-evaporation balance, spring snowmelt inputs, and synoptic-scale shifts in atmospheric circulation (Bailey et al, 2015(Bailey et al, , 2018Meyer et al, 2015;Kostrova et al, 2013;Mackay et al, 2013). It is envisaged that changes in δ 18 O diatom through time at a single site in Bolshoe Toko will B. K. Biskaborn et al: Spatial indicator distribution in Bolshoe Toko surface sediments yield insights into the long-term air temperature and palaeohydrological history of the region.…”

Synoptic and Mesoscale Mechanisms Drive Winter Precipitation δ18O/δ2H in South‐Central Alaska

“…The prevailing synopticscale circulation patterns that drive these events are known to fluctuate on diurnal to interannual and decadal time scales, and these changes are well-expressed in regional climate indices such as the NPI, PDO, and the Pacific-North American pattern (Mantua & Hare, 2002;Trenberth & Hurrell, 1994;Wallace & Gutzler, 1981). Accordingly, several paleoisotope archives from Alaska and the Yukon have been interpreted to reflect atmospheric circulation driven changes in moisture source and/or storm trajectory (Anderson et al, 2005;Bailey et al, 2018;Jones et al, 2014) and in some instances exhibit significant correlations with instrumental climate indices over the past 100 years (Bailey et al, 2015;Klein et al, 2015).…”

Dynamic Holocene Vegetation and North Pacific Hydroclimate Recorded in a Mountain Peatland, Moloka‘i, Hawai‘i

“…Reconstructed peatland water δ 2 H values suggest tradewind-dominated rainfall, similar to rainfall values at the site today. The millennium preceding arrival of the first people in Hawai'i was drier than previous times with potentially an increased frequency of stronger Aleutian Low conditions in the North Pacific (Bailey et al, 2018). Recent analysis of rainfall observations since 1920 show an overall drying in Hawai'i, including East Moloka'i (Frazier and Giambelluca, 2017), that appears to be continuing an overall drying trend in Hawaii since 1500 (Diaz et al, 2016).…”