Geografi
Iskerneboring & golfstrøm (til i morgen)
18. juni 2008 af
andreaspeter89 (Slettet)
Hej
Jeg skal op i AT i morgen under emnet global nedkøling/opvarmning og vil gerne lige vide to ting:
1
først og fremmest hvordan bestemmer man CO2 og temp. udfra iskerneboringerne og er dette en troværdig måde?
2
mere sekundært:
ville jorden gennemsnitstemp. falde hvis golfstrømmen stoppede? hvis den gjorde det ville hele det store transportbånd så stoppe - eller?
1 er vigtigtst, men om I bare kan svare på noget så skriv ;)
tak
Jeg skal op i AT i morgen under emnet global nedkøling/opvarmning og vil gerne lige vide to ting:
1
først og fremmest hvordan bestemmer man CO2 og temp. udfra iskerneboringerne og er dette en troværdig måde?
2
mere sekundært:
ville jorden gennemsnitstemp. falde hvis golfstrømmen stoppede? hvis den gjorde det ville hele det store transportbånd så stoppe - eller?
1 er vigtigtst, men om I bare kan svare på noget så skriv ;)
tak
Svar #1
19. juni 2008 af Bruger slettet (Slettet)
Her kan man læse, hvorledes CO2-indholdet i iskerner måles:
To demonstrate the methods used in dating ice-cores I will use the Vostok ice-core as an example because I found plenty of literature on it and because it is an Antarctic ice-core which was what the original post was about.
How It Was Collected
The Vostok Ice-Core was collected in East Antarctica by the Russian Antarctic expedition. The Vostok Ice-Core is 2,083 meters long and was collected in two portions: 1) 0 - 950 m in 1970-1974, 2) 950 - 2083 m in 1982-1983. The total depth of the ice sheet from which the core was collected is approximately 3,700 meters.
Experimental Methodology
The ice core was sliced into 1.5-2.0 meter segments. A discontinuous series sampled every 25 meters and a continuous series from 1,406 to 2,803 meters were then sent in solid form to Grenoble, France for further analysis.
At Grenoble the ice was put into clean stainless steel containers. The samples were crushed and then melted with the gases given off collected and saved for further analysis. The melt water was tested for chemical composition and then electrolysised.
The methods used in the determination of the ages include 18O/16O isotopic analysis [1], independent ice-flow calculations [1], comparison with other ice cores [1], paleoclimatic comparison [1], comparison with deep sea cores [1], 10Be/9Be isotopic analysis [2], deuterium/hydrogen isotopic analysis [3], comparison with marine climatic record [3], CO2 correspondances between dated ice-cores [4] and CO2 correspondances with dated oceanic cores [4].
The results determined from these various samples were consistent between the continuous and discontinuous slices within the sections that overlapped. They were also consistent with Greenland ice-cores, other Antarctic ice-cores, dated volcanic records, deep sea cores, and paleoclimatic evidence.
Results
While unable to provide specific dates (within a millenia), the analysis show definate evidence of the the last two ice ages. Using the methods listed above the bottom of the ice-core was laid down 160,000 +- 15,000 years ago. It should be noted that all of the methods listed above were consistent with the above results.
Kilde:http://www.talkorigins.org/faqs/icecores.html
To demonstrate the methods used in dating ice-cores I will use the Vostok ice-core as an example because I found plenty of literature on it and because it is an Antarctic ice-core which was what the original post was about.
How It Was Collected
The Vostok Ice-Core was collected in East Antarctica by the Russian Antarctic expedition. The Vostok Ice-Core is 2,083 meters long and was collected in two portions: 1) 0 - 950 m in 1970-1974, 2) 950 - 2083 m in 1982-1983. The total depth of the ice sheet from which the core was collected is approximately 3,700 meters.
Experimental Methodology
The ice core was sliced into 1.5-2.0 meter segments. A discontinuous series sampled every 25 meters and a continuous series from 1,406 to 2,803 meters were then sent in solid form to Grenoble, France for further analysis.
At Grenoble the ice was put into clean stainless steel containers. The samples were crushed and then melted with the gases given off collected and saved for further analysis. The melt water was tested for chemical composition and then electrolysised.
The methods used in the determination of the ages include 18O/16O isotopic analysis [1], independent ice-flow calculations [1], comparison with other ice cores [1], paleoclimatic comparison [1], comparison with deep sea cores [1], 10Be/9Be isotopic analysis [2], deuterium/hydrogen isotopic analysis [3], comparison with marine climatic record [3], CO2 correspondances between dated ice-cores [4] and CO2 correspondances with dated oceanic cores [4].
The results determined from these various samples were consistent between the continuous and discontinuous slices within the sections that overlapped. They were also consistent with Greenland ice-cores, other Antarctic ice-cores, dated volcanic records, deep sea cores, and paleoclimatic evidence.
Results
While unable to provide specific dates (within a millenia), the analysis show definate evidence of the the last two ice ages. Using the methods listed above the bottom of the ice-core was laid down 160,000 +- 15,000 years ago. It should be noted that all of the methods listed above were consistent with the above results.
Kilde:http://www.talkorigins.org/faqs/icecores.html
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