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6 records – page 1 of 1.

Source
Nature. 2008 Apr 17;452(7189):798-802
Publication Type
Article
Date
Apr-17-2008
Author
Witze Alexandra
Source
Nature. 2008 Apr 17;452(7189):798-802
Date
Apr-17-2008
Language
English
Publication Type
Article
Keywords
Geography
Greenhouse Effect
Greenland
Ice Cover
Phase Transition
Seasons
Spacecraft
Uncertainty
Water Movements
PubMed ID
18431825 View in PubMed
Less detail

The effect of permafrost thaw on old carbon release and net carbon exchange from tundra.

https://arctichealth.org/en/permalink/ahliterature88896
Source
Nature. 2009 May 28;459(7246):556-9
Publication Type
Article
Date
May-28-2009
Author
Schuur Edward A G
Vogel Jason G
Crummer Kathryn G
Lee Hanna
Sickman James O
Osterkamp T E
Author Affiliation
Department of Biology, University of Florida, Gainesville, Florida 32611, USA. tschuur@ufl.edu
Source
Nature. 2009 May 28;459(7246):556-9
Date
May-28-2009
Language
English
Publication Type
Article
Keywords
Alaska
Atmosphere - chemistry
Carbon - analysis - metabolism
Carbon Dioxide - analysis - metabolism
Carbon Radioisotopes
Cold Climate
Ecosystem
Feedback
Freezing
Greenhouse Effect
Phase Transition
Soil - analysis
Abstract
Permafrost soils in boreal and Arctic ecosystems store almost twice as much carbon as is currently present in the atmosphere. Permafrost thaw and the microbial decomposition of previously frozen organic carbon is considered one of the most likely positive climate feedbacks from terrestrial ecosystems to the atmosphere in a warmer world. The rate of carbon release from permafrost soils is highly uncertain, but it is crucial for predicting the strength and timing of this carbon-cycle feedback effect, and thus how important permafrost thaw will be for climate change this century and beyond. Sustained transfers of carbon to the atmosphere that could cause a significant positive feedback to climate change must come from old carbon, which forms the bulk of the permafrost carbon pool that accumulated over thousands of years. Here we measure net ecosystem carbon exchange and the radiocarbon age of ecosystem respiration in a tundra landscape undergoing permafrost thaw to determine the influence of old carbon loss on ecosystem carbon balance. We find that areas that thawed over the past 15 years had 40 per cent more annual losses of old carbon than minimally thawed areas, but had overall net ecosystem carbon uptake as increased plant growth offset these losses. In contrast, areas that thawed decades earlier lost even more old carbon, a 78 per cent increase over minimally thawed areas; this old carbon loss contributed to overall net ecosystem carbon release despite increased plant growth. Our data document significant losses of soil carbon with permafrost thaw that, over decadal timescales, overwhelms increased plant carbon uptake at rates that could make permafrost a large biospheric carbon source in a warmer world.
PubMed ID
19478781 View in PubMed
Less detail

Hydrology and the future of the Greenland Ice Sheet.

https://arctichealth.org/en/permalink/ahliterature296558
Source
Nat Commun. 2018 07 16; 9(1):2729
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
07-16-2018
Author
Gwenn E Flowers
Author Affiliation
Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada. gflowers@sfu.ca.
Source
Nat Commun. 2018 07 16; 9(1):2729
Date
07-16-2018
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Global Warming - statistics & numerical data
Greenland
Humans
Hydrology
Ice Cover - chemistry
Models, Statistical
Phase Transition
Seawater - analysis
Time Factors
Water Movements
Abstract
Detection, attribution and projection of mass loss from the Greenland Ice Sheet has been a central focus of the glaciological community, with surface meltwater thought to play a key role in feedbacks that could accelerate sea-level rise. While the prospect of runaway sliding has faded, much remains uncertain when it comes to the role of surface runoff and subglacial discharge in Greenland's future.
PubMed ID
30013134 View in PubMed
Less detail

Intensity of quartz-tungsten-halogen light-curing units used in private practice in Toronto.

https://arctichealth.org/en/permalink/ahliterature173824
Source
J Am Dent Assoc. 2005 Jun;136(6):766-73; quiz 806-7
Publication Type
Article
Date
Jun-2005
Author
Omar El-Mowafy
Wafa El-Badrawy
Donald W Lewis
Babak Shokati
Jaffer Kermalli
Osama Soliman
Avedis Encioiu
Avides Encioiu
Rema Zawi
Fatma Rajwani
Author Affiliation
Restorative Dentistry, University of Toronto, Faculty of Dentistry, Toronto, Ontario, Canada. oel.mowafy@utoronto.ca
Source
J Am Dent Assoc. 2005 Jun;136(6):766-73; quiz 806-7
Date
Jun-2005
Language
English
Publication Type
Article
Keywords
Analysis of Variance
Chi-Square Distribution
Composite Resins - radiation effects
Dental Equipment
Equipment Safety
General Practice, Dental
Glare
Halogens
Hot Temperature
Humans
Light
Linear Models
Ontario
Phase Transition
Private Practice
Quartz
Radiation monitoring
Tungsten
Abstract
The authors conducted a study to determine light intensity and heat/glare measurements of quartztungsten-halogen (QTH) light polymerization units used in dental offices.
Research assistants visited 100 dental offices and assessed 214 QTH light units. They recorded each unit's model, age, service history, light intensity and heat/glare emissions.
Mean light intensity was 526 milliwatts per square centimeter (120-1,000 mW/cm2), with 26 units having intensity less than 300 mW/cm2. The mean light unit age was 5.6 years. Light units older than three years had significantly lower output intensities than those that were one, two or three years old. The authors found a wide range of heat/glare measurements (3-300 mW/cm2), with 4.6 percent of the units having values greater than 50 mW/cm2, including three with values of more than 200 mW/cm2. The mean light intensity of units serviced in the preceding year was 539 mW/cm2; it was 418 mW/cm2 for units serviced from one to six years previously.
Light intensity and heat/glare values varied among the 214 units; some units had values well outside the recommended levels. Each unit's age and service history significantly affected its intensity. An awareness campaign is needed to promote testing, repair or replacement of light polymerization units. Periodic testing of light polymerization units should be considered by regulatory bodies to ensure optimum quality of composite restorations.
Light polymerization units in some private dental offices in Toronto had intensities that may result in composites restorations with inferior properties. Dentists need to regularly monitor the intensity of the light polymerization units and maintain the units to ensure quality composite restorations.
Notes
Erratum In: J Am Dent Assoc. 2005 Aug;136(8):1086Encioiu, Avides [corrected to Encioiu, Avedis]
PubMed ID
16022041 View in PubMed
Less detail

[Modeling the Propagation of Microbial Cells and Phage Particles from the Sites of Permafrost Thawing.]

https://arctichealth.org/en/permalink/ahliterature289688
Source
Mikrobiologiia. 2016 Sep; 85(5):580-587
Publication Type
Journal Article
Date
Sep-2016
Author
D A Skladnev
A L Mulyukin
S N Filippoval
E E Kulikov
M A Letaroval
E A Yuzbasheva
E A Karnysheva
A V Brushkov
V F Gal'chenko
Source
Mikrobiologiia. 2016 Sep; 85(5):580-587
Date
Sep-2016
Language
Russian
Publication Type
Journal Article
Keywords
Coliphages - physiology
Corynebacterium - physiology
Ice - analysis
Models, Biological
Movement - physiology
Organisms, Genetically Modified
Permafrost - microbiology
Phase Transition
Rheology - methods
Rivers - microbiology
Seasons
Siberia
Yarrowia - physiology
Abstract
A method is proposed for integral assessment of the propagation of microbial cells and viral parti- cles during seasonal thawing of relic ice wedge layers. The results of on-site and laboratory investigation car- ried out in the upper part of permafrost exposure at Mamontova Gora (Yakutiya, Russia) are presented. To increase reliability of the results, suspensions of two microbial species and two coliphage species were intro- duced as biomarkers directly on the surface of thaing ice and in the meltwater flow. Each of the four different model biological objects was shown to possess unique parameters of movement in the meltwater flow and is able to move 132 m in 25-35 min with the water flow.
PubMed ID
29364605 View in PubMed
Less detail

[Modeling the Propagation of Microbial Cells and Phage Particles from the Sites of Permafrost Thawing.]

https://arctichealth.org/en/permalink/ahliterature289530
Source
Mikrobiologiia. 2016 Sep; 85(5):580-587
Publication Type
Journal Article
Date
Sep-2016
Author
D A Skladnev
A L Mulyukin
S N Filippoval
E E Kulikov
M A Letaroval
E A Yuzbasheva
E A Karnysheva
A V Brushkov
V F Gal'chenko
Source
Mikrobiologiia. 2016 Sep; 85(5):580-587
Date
Sep-2016
Language
Russian
Publication Type
Journal Article
Keywords
Coliphages - physiology
Corynebacterium - physiology
Ice - analysis
Models, Biological
Movement - physiology
Organisms, Genetically Modified
Permafrost - microbiology
Phase Transition
Rheology - methods
Rivers - microbiology
Seasons
Siberia
Yarrowia - physiology
Abstract
A method is proposed for integral assessment of the propagation of microbial cells and viral parti- cles during seasonal thawing of relic ice wedge layers. The results of on-site and laboratory investigation car- ried out in the upper part of permafrost exposure at Mamontova Gora (Yakutiya, Russia) are presented. To increase reliability of the results, suspensions of two microbial species and two coliphage species were intro- duced as biomarkers directly on the surface of thaing ice and in the meltwater flow. Each of the four different model biological objects was shown to possess unique parameters of movement in the meltwater flow and is able to move 132 m in 25-35 min with the water flow.
PubMed ID
29364605 View in PubMed
Less detail

6 records – page 1 of 1.