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A 700-year paleoecological record of boreal ecosystem responses to climatic variation from Alaska.

https://arctichealth.org/en/permalink/ahliterature85780
Source
Ecology. 2008 Mar;89(3):729-43
Publication Type
Article
Date
Mar-2008
Author
Tinner Willy
Bigler Christian
Gedye Sharon
Gregory-Eaves Irene
Jones Richard T
Kaltenrieder Petra
Krähenbühl Urs
Hu Feng Sheng
Author Affiliation
Institute of Plant Sciences and Oeschger Center for Climate Change Research, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland. willy.tinner@ips.unibe.ch
Source
Ecology. 2008 Mar;89(3):729-43
Date
Mar-2008
Language
English
Publication Type
Article
Keywords
Alaska
Climate
Diatoms
Ecosystem
Fires
Forestry
Fossils
Geologic sediments
Greenhouse Effect
Ice Cover
Plant Physiology
Pollen
Time Factors
Trees
Abstract
Recent observations and model simulations have highlighted the sensitivity of the forest-tundra ecotone to climatic forcing. In contrast, paleoecological studies have not provided evidence of tree-line fluctuations in response to Holocene climatic changes in Alaska, suggesting that the forest-tundra boundary in certain areas may be relatively stable at multicentennial to millennial time scales. We conducted a multiproxy study of sediment cores from an Alaskan lake near the altitudinal limits of key boreal-forest species. Paleoecological data were compared with independent climatic reconstructions to assess ecosystem responses of the forest tundra boundary to Little Ice Age (LIA) climatic fluctuations. Pollen, diatom, charcoal, macrofossil, and magnetic analyses provide the first continuous record of vegetation fire-climate interactions at decadal to centennial time scales during the past 700 years from southern Alaska. Boreal-forest diebacks characterized by declines of Picea mariana, P. glauca, and tree Betula occurred during the LIA (AD 1500-1800), whereas shrubs (Alnus viridis, Betula glandulosa/nana) and herbaceous taxa (Epilobium, Aconitum) expanded. Marked increases in charcoal abundance and changes in magnetic properties suggest increases in fire importance and soil erosion during the same period. In addition, the conspicuous reduction or disappearance of certain aquatic (e.g., Isoetes, Nuphar, Pediastrum) and wetland (Sphagnum) plants and major shifts in diatom assemblages suggest pronounced lake-level fluctuations and rapid ecosystem reorganization in response to LIA climatic deterioration. Our results imply that temperature shifts of 1-2 degrees C, when accompanied by major changes in moisture balance, can greatly alter high-altitudinal terrestrial, wetland, and aquatic ecosystems, including conversion between boreal-forest tree line and tundra. The climatic and ecosystem variations in our study area appear to be coherent with changes in solar irradiance, suggesting that changes in solar activity contributed to the environmental instability of the past 700 years.
PubMed ID
18459336 View in PubMed
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Activity and diversity of methane-oxidizing bacteria along a Norwegian sub-Arctic glacier forefield.

https://arctichealth.org/en/permalink/ahliterature299197
Source
FEMS Microbiol Ecol. 2018 05 01; 94(5):
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
05-01-2018
Author
Alejandro Mateos-Rivera
Lise Øvreås
Bryan Wilson
Jacob C Yde
Kai W Finster
Author Affiliation
Department of Biology, University of Bergen, NO-5020, Bergen, Norway.
Source
FEMS Microbiol Ecol. 2018 05 01; 94(5):
Date
05-01-2018
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Arctic Regions
Biodiversity
High-Throughput Nucleotide Sequencing
Ice Cover - microbiology
Methane - metabolism
Methylococcaceae - classification - genetics - isolation & purification
Norway
Soil Microbiology
Abstract
Methane (CH4) is one of the most abundant greenhouse gases in the atmosphere and identification of its sources and sinks is crucial for the reliability of climate model outputs. Although CH4 production and consumption rates have been reported from a broad spectrum of environments, data obtained from glacier forefields are restricted to a few locations. We report the activities of methanotrophic communities and their diversity along a chronosequence in front of a sub-Arctic glacier using high-throughput sequencing and gas flux measurements. CH4 oxidation rates were measured in the field throughout the growing season during three sampling times at eight different sampling points in combination with laboratory incubation experiments. The overall results showed that the methanotrophic community had similar trends of increased CH4 consumption and increased abundance as a function of soil development and time of year. Sequencing results revealed that the methanotrophic community was dominated by a few OTUs and that a short-term increase in CH4 concentration, as performed in the field measurements, altered slightly the relative abundance of the OTUs.
PubMed ID
29617984 View in PubMed
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Algae are melting away the Greenland ice sheet.

https://arctichealth.org/en/permalink/ahliterature275518
Source
Nature. 2016 Jul 21;535(7612):336
Publication Type
Article
Date
Jul-21-2016

Algal photophysiology drives darkening and melt of the Greenland Ice Sheet.

https://arctichealth.org/en/permalink/ahliterature306814
Source
Proc Natl Acad Sci U S A. 2020 03 17; 117(11):5694-5705
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
03-17-2020
Author
Christopher J Williamson
Joseph Cook
Andrew Tedstone
Marian Yallop
Jenine McCutcheon
Ewa Poniecka
Douglas Campbell
Tristram Irvine-Fynn
James McQuaid
Martyn Tranter
Rupert Perkins
Alexandre Anesio
Author Affiliation
Bristol Glaciology Centre, University of Bristol, Bristol BS8 1HH, United Kingdom; c.williamson@bristol.ac.uk.
Source
Proc Natl Acad Sci U S A. 2020 03 17; 117(11):5694-5705
Date
03-17-2020
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Feedback, Physiological
Greenland
Ice Cover
Microalgae - metabolism - physiology
Photosynthesis
Sea level rise
Abstract
Blooms of Zygnematophycean "glacier algae" lower the bare ice albedo of the Greenland Ice Sheet (GrIS), amplifying summer energy absorption at the ice surface and enhancing meltwater runoff from the largest cryospheric contributor to contemporary sea-level rise. Here, we provide a step change in current understanding of algal-driven ice sheet darkening through quantification of the photophysiological mechanisms that allow glacier algae to thrive on and darken the bare ice surface. Significant secondary phenolic pigmentation (11 times the cellular content of chlorophyll a) enables glacier algae to tolerate extreme irradiance (up to ~4,000 µmol photons·m-2·s-1) while simultaneously repurposing captured ultraviolet and short-wave radiation for melt generation. Total cellular energy absorption is increased 50-fold by phenolic pigmentation, while glacier algal chloroplasts positioned beneath shading pigments remain low-light-adapted (Ek ~46 µmol photons·m-2·s-1) and dependent upon typical nonphotochemical quenching mechanisms for photoregulation. On the GrIS, glacier algae direct only ~1 to 2.4% of incident energy to photochemistry versus 48 to 65% to ice surface melting, contributing an additional ~1.86 cm water equivalent surface melt per day in patches of high algal abundance (~104 cells·mL-1). At the regional scale, surface darkening is driven by the direct and indirect impacts of glacier algae on ice albedo, with a significant negative relationship between broadband albedo (Moderate Resolution Imaging Spectroradiometer [MODIS]) and glacier algal biomass (R2 = 0.75, n = 149), indicating that up to 75% of the variability in albedo across the southwestern GrIS may be attributable to the presence of glacier algae.
PubMed ID
32094168 View in PubMed
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Alpine soil microbial ecology in a changing world.

https://arctichealth.org/en/permalink/ahliterature301151
Source
FEMS Microbiol Ecol. 2018 09 01; 94(9):
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Review
Date
09-01-2018
Author
Johanna Donhauser
Beat Frey
Author Affiliation
Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
Source
FEMS Microbiol Ecol. 2018 09 01; 94(9):
Date
09-01-2018
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Review
Keywords
Arctic Regions
Biodiversity
Climate change
Ice Cover
Permafrost - chemistry - microbiology
Soil Microbiology
Tundra
Abstract
Climate change has a disproportionally large impact on alpine soil ecosystems, leading to pronounced changes in soil microbial diversity and function associated with effects on biogeochemical processes at the local and supraregional scales. However, due to restricted accessibility, high-altitude soils remain largely understudied and a considerable heterogeneity hampers the comparability of different alpine studies. Here, we highlight differences and similarities between alpine and arctic ecosystems, and we discuss the impact of climatic variables and associated vegetation and soil properties on microbial ecology. We consider how microbial alpha-diversity, community structures and function change along altitudinal gradients and with other topographic features such as slope aspect. In addition, we focus on alpine permafrost soils, harboring a surprisingly large unknown microbial diversity and on microbial succession along glacier forefield chronosequences constituting the most thoroughly studied alpine habitat. Finally, highlighting experimental approaches, we present climate change studies showing shifts in microbial community structures and function in response to warming and altered moisture, interestingly with some contradiction. Collectively, despite harsh environmental conditions, many specially adapted microorganisms are able to thrive in alpine environments. Their community structures strongly correlate with climatic, vegetation and soil properties and thus closely mirror the complexity and small-scale heterogeneity of alpine soils.
PubMed ID
30032189 View in PubMed
Less detail
Source
Curr Biol. 2013 Dec 2;23(23):R1020-22
Publication Type
Article
Date
Dec-2-2013
Author
Cyrus Martin
Source
Curr Biol. 2013 Dec 2;23(23):R1020-22
Date
Dec-2-2013
Language
English
Publication Type
Article
Keywords
Arctic Regions
Geologic sediments
Global warming
Greenhouse Effect
Humans
Ice Cover
Lakes
PubMed ID
24455769 View in PubMed
Less detail

Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years.

https://arctichealth.org/en/permalink/ahliterature294791
Source
Nature. 2018 04; 556(7700):227-230
Publication Type
Historical Article
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Date
04-2018
Author
David J R Thornalley
Delia W Oppo
Pablo Ortega
Jon I Robson
Chris M Brierley
Renee Davis
Ian R Hall
Paola Moffa-Sanchez
Neil L Rose
Peter T Spooner
Igor Yashayaev
Lloyd D Keigwin
Author Affiliation
Department of Geography, University College London, London, UK. d.thornalley@cantab.net.
Source
Nature. 2018 04; 556(7700):227-230
Date
04-2018
Language
English
Publication Type
Historical Article
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Keywords
Arctic Regions
Atlantic Ocean
Climate Change - statistics & numerical data
Convection
Fresh Water - analysis
Greenland
History, 15th Century
History, 16th Century
History, 17th Century
History, 18th Century
History, 19th Century
History, 20th Century
History, 21st Century
History, Medieval
Ice Cover - chemistry
Newfoundland and Labrador
Oceans and Seas
Reproducibility of Results
Seawater - analysis
Time Factors
Water Movements
Abstract
The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that has an essential role in Earth's climate, redistributing heat and influencing the carbon cycle1, 2. The AMOC has been shown to be weakening in recent years 1 ; this decline may reflect decadal-scale variability in convection in the Labrador Sea, but short observational datasets preclude a longer-term perspective on the modern state and variability of Labrador Sea convection and the AMOC1, 3-5. Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately AD 1850) compared with the preceding 1,500 years. Our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the LIA, or as a more gradual, continued decline over the past 150 years; this ambiguity probably arises from non-AMOC influences on the various proxies or from the different sensitivities of these proxies to individual components of the AMOC. We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA-sourced from melting glaciers and thickened sea ice that developed earlier in the LIA-weakened Labrador Sea convection and the AMOC. The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet 6 . Our results suggest that recent decadal variability in Labrador Sea convection and the AMOC has occurred during an atypical, weak background state. Future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the AMOC weakening described here.
Notes
CommentIn: Nature. 2018 Apr;556(7700):149 PMID 29643490
CommentIn: Nature. 2018 Apr;556(7700):180-181 PMID 29636556
PubMed ID
29643484 View in PubMed
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Anthropogenic radioactive isotopes in Actiniaria from the Svalbard archipelago.

https://arctichealth.org/en/permalink/ahliterature305349
Source
Mar Pollut Bull. 2020 Aug; 157:111369
Publication Type
Journal Article
Date
Aug-2020
Author
M Saniewski
P Balazy
D Saniewska
Author Affiliation
Institute of Meteorology and Water Management - National Research Institute, Waszyngtona 42, 81-342 Gdynia, Poland. Electronic address: michal.saniewski@imgw.pl.
Source
Mar Pollut Bull. 2020 Aug; 157:111369
Date
Aug-2020
Language
English
Publication Type
Journal Article
Keywords
Animals
Arctic Regions
Cesium Radioisotopes - analysis
Ice Cover
Radiation monitoring
Sea Anemones
Svalbard
Water Pollutants, Radioactive - analysis
Abstract
The abundance of radionuclides in the Arctic Actiniaria has limited study despite their environmental importance in coastal food chains. Although the Arctic has incurred relatively little contamination by anthropogenic radionuclides as a result of nuclear weapons tests, there are still detectable levels of radionuclide activity observed in marine species. In this study of anthropogenic radionuclide activity in Actiniaria from Spitsbergen we observed levels of 90Sr from 0.92 Bq kg-1dw to 18 Bq kg-1dw and for 137Cs from 1.2 Bq kg-1dw to 12 Bq kg-1dw. The highest values of 90Sr and 137Cs were observed in organisms at stations close to seabird colonies and a river mouth, suggesting that fecal material and melting glaciers may be sources of radionuclides in the Arctic environment. The body mass of individual organisms affected bioaccumulation of 90Sr and 137Cs in Actiniaria, with radionuclide bioaccumulation occurring most intensively in the smaller specimens.
PubMed ID
32658712 View in PubMed
Less detail
Source
Science. 2014 Feb 28;343(6174):979-80
Publication Type
Article
Date
Feb-28-2014
Author
John F Hoffecker
Scott A Elias
Dennis H O'Rourke
Author Affiliation
Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.
Source
Science. 2014 Feb 28;343(6174):979-80
Date
Feb-28-2014
Language
English
Publication Type
Article
Keywords
Alaska
Anthropology
DNA, Mitochondrial - genetics
Human Migration
Humans
Ice Cover
Indians, North American - genetics
Islands
North America
Oceans and Seas
Reproductive Isolation
Trees
PubMed ID
24578571 View in PubMed
Less detail

345 records – page 1 of 35.