Dataset Information

Enhanced North Pacific subtropical gyre circulation during the late Holocene.

ABSTRACT: The North Pacific Subtropical Gyre circulation redistributes heat from the Western Pacific Warm Pool towards the mid- to high-latitude North Pacific. However, the driving mechanisms of this circulation and how it changed over the Holocene remain poorly understood. Here, we present alkenone-based sea surface temperature reconstructions along the Kuroshio, California and Alaska currents that cover the past ~7,000 years. These and other paleorecords collectively demonstrate a coherent intensification of the boundary currents, and thereby the basin-scale subtropical gyre circulation, since ~3,000-4,000 years ago. Such enhanced circulation during the late Holocene appears to have resulted from a long-term southward migration of the Intertropical Convergence Zone, associated with Holocene ocean cooling. Our results imply that the North Pacific Subtropical Gyre circulation could be weakened under future global warming.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC8511172 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Enhanced North Pacific subtropical gyre circulation during the late Holocene.

Zhang Yancheng Y Zheng Xufeng X Kong Deming D Yan Hong H Liu Zhonghui Z

Nature communications 20211012 1

The North Pacific Subtropical Gyre circulation redistributes heat from the Western Pacific Warm Pool towards the mid- to high-latitude North Pacific. However, the driving mechanisms of this circulation and how it changed over the Holocene remain poorly understood. Here, we present alkenone-based sea surface temperature reconstructions along the Kuroshio, California and Alaska currents that cover the past ~7,000 years. These and other paleorecords collectively demonstrate a coherent intensificati ...[more]

PMID: 34642314

Similar Datasets

Project description:The summertime North Pacific subtropical gyre has widespread phytoplankton blooms between Hawaii and the subtropical front (?30°N) that appear as chlorophyll (chl) increases in satellite ocean color data. Nitrogen-fixing diatom symbioses (diatom-diazotroph associations: DDAs) often increase 10(2)-10(3) fold in these blooms and contribute to elevated export flux. In 2008 and 2009, two cruises targeted satellite chlorophyll blooms to examine DDA species abundance, chlorophyll concentration, biogenic silica concentration, and hydrography. Generalized observations that DDA blooms occur when the mixed layer depth is < 70 m are supported, but there is no consistent relationship between mixed layer depth, bloom intensity, or composition; regional blooms between 22-34°N occur within a broader temperature range (21-26°C) than previously reported. In both years, the Hemiaulus-Richelia and Rhizosolenia-Richelia DDAs increased 10(2)-10(3) over background concentrations within satellite-defined bloom features. The two years share a common trend of Hemiaulus dominance of the DDAs and substantial increases in the >10 µm chl a fraction (?40-90+% of total chl a). Integrated diatom abundance varied 10-fold over <10 km. Biogenic silica concentration tracked diatom abundance, was dominated by the >10 µm size fraction, and increased up to 5-fold in the blooms. The two years differed in the magnitude of the surface chl a increase (2009>2008), the abundance of pennate diatoms within the bloom (2009>2008), and the substantially greater mixed layer depth in 2009. Only the 2009 bloom had sufficient chl a in the >10 µm fraction to produce the observed ocean color chl increase. Blooms had high spatial variability; ocean color images likely average over numerous small events over time and space scales that exceed the individual event scale. Summertime DDA export flux noted at the Hawaii time-series Sta. ALOHA is probably a generalized feature of the eastern N. Pacific north to the subtropical front.

Project description:Filamentous diazotrophic Cyanobacteria of the genus Trichodesmium, often found in colonial form, provide an important source of new nitrogen to tropical and subtropical marine ecosystems. Colonies are composed of several clades of Trichodesmium in association with a diverse community of bacterial and eukaryotic epibionts. We used high-throughput 16S rRNA and nifH gene sequencing, carbon (C) and dinitrogen (N2) fixation assays, and metagenomics to describe the diversity and functional potential of the microbiome associated with Trichodesmium colonies collected from the North Pacific Subtropical Gyre (NPSG). The 16S rRNA and nifH gene sequences from hand-picked colonies were predominantly (>99%) from Trichodesmium Clade I (i.e., T. thiebautii), which is phylogenetically and ecologically distinct from the Clade III IMS101 isolate used in most laboratory studies. The bacterial epibiont communities were dominated by Bacteroidetes, Alphaproteobacteria, and Gammaproteobacteria, including several taxa with a known preference for surface attachment, and were relatively depleted in the unicellular Cyanobacteria and small photoheterotrophic bacteria that dominate NPSG surface waters. Sequencing the nifH gene (encoding a subcomponent of the nitrogenase enzyme) identified non-Trichodesmium diazotrophs that clustered predominantly among the Cluster III nifH sequence-types that includes putative anaerobic diazotrophs. Trichodesmium colonies may represent an important habitat for these Cluster III diazotrophs, which were relatively rare in the surrounding seawater. Sequence analyses of nifH gene transcripts revealed several cyanobacterial groups, including heterocystous Richelia, associated with the colonies. Both the 16S rRNA and nifH datasets indicated strong differences between Trichodesmium epibionts and picoplankton in the surrounding seawater, and also between the epibionts inhabiting Trichodesmium puff and tuft colony morphologies. Metagenomic and 16S rRNA gene sequence analyses suggested that lineages typically associated with a copiotrophic lifestyle comprised a large fraction of colony-associated epibionts, in contrast to the streamlined genomes typical of bacterioplankton in these oligotrophic waters. Additionally, epibiont metagenomes were enriched in specific genes involved in phosphate and iron acquisition and denitrification pathways relative to surface seawater metagenomes. We propose that the unique microbial consortium inhabiting colonies has a significant impact on the biogeochemical functioning of Trichodesmium colonies in pelagic environments.

Dataset Information

Enhanced North Pacific subtropical gyre circulation during the late Holocene.

Publications

Enhanced North Pacific subtropical gyre circulation during the late Holocene.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets