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239 records – page 1 of 24.

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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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
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
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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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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
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An ultra-clean firn core from the Devon Island Ice Cap, Nunavut, Canada, retrieved using a titanium drill specially designed for trace element studies.

https://arctichealth.org/en/permalink/ahliterature82660
Source
J Environ Monit. 2006 Mar;8(3):406-13
Publication Type
Article
Date
Mar-2006
Author
Zheng J.
Fisher D.
Blake E.
Hall G.
Vaive J.
Krachler M.
Zdanowicz C.
Lam J.
Lawson G.
Shotyk W.
Author Affiliation
GSC Northern Canada, Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, Canada K1A 0E8. jzheng@nrcan.gc.ca
Source
J Environ Monit. 2006 Mar;8(3):406-13
Date
Mar-2006
Language
English
Publication Type
Article
Keywords
Air Pollutants - analysis
Arctic Regions
Cadmium - analysis
Environmental Monitoring - instrumentation - methods
Ice Cover - chemistry
Lead - analysis
Metals - analysis
Nunavut
Time Factors
Titanium
Abstract
An electromechanical drill with titanium barrels was used to recover a 63.7 m long firn core from Devon Island Ice Cap, Nunavut, Canada, representing 155 years of precipitation. The core was processed and analysed at the Geological Survey of Canada by following strict clean procedures for measurements of Pb and Cd at concentrations at or below the pg g(-1) level. This paper describes the effectiveness of the titanium drill with respect to contamination during ice core retrieval and evaluates sample-processing procedures in laboratories. The results demonstrate that: (1) ice cores retrieved with this titanium drill are of excellent quality with metal contamination one to four orders of magnitude less than those retrieved with conventional drills; (2) the core cleaning and sampling protocols used were effective, contamination-free, and adequate for analysis of the metals (Pb and Cd) at low pg g(-1) levels; and (3) results from 489 firn core samples analysed in this study are comparable with published data from other sites in the Arctic, Greenland and the Antarctic.
PubMed ID
16528426 View in PubMed
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Arctic climate change and its impacts.

https://arctichealth.org/en/permalink/ahliterature95820
Source
Ambio. 2004 Nov;33(7):1 p following 479
Publication Type
Article
Date
Nov-2004

Arctic lake physical processes and regimes with implications for winter water availability and management in the National Petroleum Reserve Alaska.

https://arctichealth.org/en/permalink/ahliterature90679
Source
Environ Manage. 2009 Jun;43(6):1071-84
Publication Type
Article
Date
Jun-2009
Author
Jones Benjamin M
Arp Christopher D
Hinkel Kenneth M
Beck Richard A
Schmutz Joel A
Winston Barry
Author Affiliation
Alaska Science Center, U.S. Geological Survey, 4210 University Drive, Anchorage, AK 99508-4664, USA. bjones@usgs.gov
Source
Environ Manage. 2009 Jun;43(6):1071-84
Date
Jun-2009
Language
English
Publication Type
Article
Keywords
Alaska
Arctic Regions
Conservation of Natural Resources
Fresh Water
Geography
Ice Cover
Petroleum
Seasons
Time Factors
Weather
Abstract
Lakes are dominant landforms in the National Petroleum Reserve Alaska (NPRA) as well as important social and ecological resources. Of recent importance is the management of these freshwater ecosystems because lakes deeper than maximum ice thickness provide an important and often sole source of liquid water for aquatic biota, villages, and industry during winter. To better understand seasonal and annual hydrodynamics in the context of lake morphometry, we analyzed lakes in two adjacent areas where winter water use is expected to increase in the near future because of industrial expansion. Landsat Thematic Mapper and Enhanced Thematic Mapper Plus imagery acquired between 1985 and 2007 were analyzed and compared with climate data to understand interannual variability. Measured changes in lake area extent varied by 0.6% and were significantly correlated to total precipitation in the preceding 12 months (p
PubMed ID
19101761 View in PubMed
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239 records – page 1 of 24.