Nitrogenous chemical composition of antarctic Ice and ...
compositions indicate that they are extraterrestrial, but most of these probably are meteoroid ablation products (figure 3) or particles produced by the breakup of fragile sporadic meteoroids in the Earth's atmosphere. During the coming months, we will characterize a large number of particles from the 1833 layer for morphology and chemistry, attempting to identify a population of particles that may be derived from the cometary Leonid shower. If we find a particle population that appears likely to be cometary material, we will analyze particles from another ice layer that has the same advantages as the 1833 layer to see if the same type of particle population is present. We believe this approach—using the antarctic ice core samples—is the only method of analysis that has a chance to identify cometary material with a high degree of probability. This research is supported by National Science Foundation grant DPP 78-20410.
Nitrogenous chemical composition of antarctic Ice and snow
Figure 3. Predominantly iron spherule, probably a product of atmospheric ablation of a sporadic meteoroid. Background is nucleopore filter paper, magnification 9,800X.
University of Kansas Space Technology Center Lawrence, Kansas 66045
Earlier (Parker and Zeller 1980) we summarized our analytical data, showing that short-term and long-term fluctuations in N0 and NH occur not only in South Pole snow and firn, but in snow and snowpit samples from locations in Antarctica and in Dome C firn core material. Mean value ranges differed from one location to the next, and winter and summer snows showed variation in NO , suggesting a seasonal fallout of N0 during spring. We also listed 12 possible origins of fixed nitrogen, estimating the probability of each being a source for the antarctic ice sheet. In situ N0 and NH production, core contamination, and NO production by lightning were three sources essentially ruled out; denitrification of soils, global anthropogenic and pollutional sources, and volcanic activity (for NH )—all with atmospheric transport—were considered unlikely as major sources as was photochemical NO production.
Our objectives include an understanding of (1) the nitrogenous chemical content of snow and ice of different ages and from different geographic locations, (2) their concentration ranges and periodic and nonperiodic fluctuations, and, as far as possible, (3) their sources and the mechanisms that cause these fluctuations. Details of the above and some of our data, especially concerning fluctuations in the concentrations of nitrate (NO) and ammonium ions (NH+4 ) in a South Pole firn core and snow from other sites in Antarctica have been discusssed previously (Parker and Zeller 1980; Parker, Zeller, Harrower, and Thompson 1978; Parker, Zeller, Heiskell, and Thompson 1977, 1978a, 1978b; Zeller and Parker 1979).
With respect to the remaining potential sources listed, N0 production by meteoroids or by X- and fly-rays from supernovas were considered possible. Rood, Sarazin, Zeller, and Parker (1979) have elaborated on the supernova possibility. Also, we have detected NO 3-concentration peaks at 51, 54, and 100 meters in a 1978-79 110-meter South Pole firn core which come close to the 1974 firn core N0 spikes suggested by Rood, etal. (1979), and which may relate to the supernovas SN 1604 (Kepler), SN 1572 (Tycho) and SN 1181. The NO spike at 83 meters (around 1300 A.D.), for which Rood et al. (1978) found no record of a supernova, is absent from our 1978-79 firn core. However, we find a number of other spikes, probably due to the use of higher resolution analytical techniques.
B. C. PARKER
Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 E. J . ZELLER
1980 REVIEW
79
Finally, we have suggested solar-activity-induced fixation by auroras and/or marine aerosols as probable major sources or mechanisms for the apparent 10-11 and 20-22 year periodicity in NO fluctuations in antarctic snow and firm (Parker and Zeller 1980; Parker et al. 1978a; Zeller and Parker 1979). Solar-induced aurora! NO (and NOT) production with fallout in antarctic snow was first suggested by Wilson and House (1965); however, this mechanism has not been accepted by many who claim a 12th possible source on our list, namely production of N0 by galactic cosmic rays (Bauer 1978; Parker, et al. 1978b). We shall address this controversy in more detail. The figure shows a computer plot of NO (as micrograms of nitrogen per square decimeter per year) from our 1979-80 snowpit samples and the annual sunspot numbers. These values are means of several samples. In all previous publications we have presented our data in micrograms of nitrogen per liter (parts per billion). However, we have noted that the annual snow accumulation at the South Pole usually reaches a maximum at approximately the time when solar activity is highest. Because one can see the annual layers, as well as seasonal layers, and measure their mean thicknesses in snowpits, one can calculate the approximate concentration of a chemical constituent per area per year. The figure shows that maximum NO fallout occurred about 2 years following the two last sunspot maxima, which coincides rather well with the aurora! maxima. In contrast, lowest N0 occurred during periods of low solar activity when maximum galactic cosmic ray fluxes penetrate the Earth's atmosphere. These data cannot be accepted as a generalization until they are repeated extensively at several locations to eliminate chance occurrences. We plan to do so at South Pole in deeper pits, including the last five or more solar maxima. If we can repeat the findings shown in the figure, we shall have support for the major
source of NO in antarctic snow, firn, and ice being solaractivity-induced auroras, and not galactic cosmic rays. From the same 1979-80 snowpit, seasonal sampling for 1962 showed that NO (in micrograms of nitrogen per square decimeter) was higher during July-October than other seasons, the lowest being November-December. This finding confirms our earlier observation (Parker and Zeller 1980) and agrees with earlier arguments (Parker et al. 1978b) that photodestruction of NO,, does not occur in polar regions during winter darkness. However, these observations must be repeated many times at several locations to confirm this as a valid generalization. Sodium (NA) and magnesium analysis by atomic absorbtion spectroscopy did not show a strong correlation with the higher NO NO-3 -3 values. This suggests that marine aerosols probably do not contribute a significant proportion to the NO concentration fluctuations observed. Moreover, in a 1978-79 110-meter South Pole firn core, our lowest NO and highest Nit values occurred within the same interval of 34- to 39-meter depth. Whether this interval, and that proceeding deeper to 42 meters, also with lower NO levels, could be the interval of the "Little Ice Age" or "Maunder Minimum" in solar activity when sunspots and auroras were reduced (Eddy 1977), we cannot positively confirm. However, the frequent high Na levels during the period of about 50 years that this 34- to 39-meter layer was deposited suggests a higher frequency of marine storms over the south polar cap. Plasma emission analysis of select pooled samples for Al, an element of crustal origin, also shows higher than normal levels at South Pole in the 34- to 39-meter low NOR, high Na firn core section. We hope to have a more precise date for various depths of two 1979-80 South Pole firn cores (32 and 43 meters) in which Anthony Cow (Cold Regions Research Engineering Laboratory) has
30 W '-
H
25
-J C/) E
< 20 CD 0 Ci
Z 0 H
Iz W
15
10 5
0 C-)
1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 197 1978 APPROXIMATE YEARS BY SNOW STRATIGRAPHY
80
Sunspot activity curve (diamonds) superimposed on curve of nitrate, per square decimeter, 1919410 snowpit, South Pole Station.
ANmRcTIc JOURNAL
measured the annual layers. We also may be able to detect annual layers in 101- and 57-meter Vostok firn cores collected in 1979-80, now stored and awaiting analysis at Virginia Polytechnic Institute and State University. Detailed findings will be reported later (Parker et al. in preparation). This research was supported by National Science Foundation grant DPI' 78-21417. William Thompson, Lawson Baily, Calvin Glattfelder, and Lawrence Heiskell provided field and laboratory assistance. Anthony Cow and James Cragin gave advice and expert assistance on our future research aims. References Bauer, E. 1978. Non-biogenic fixed nitrogen in antarctic surface waters. Nature, 276, %-97. Eddy, J. A. 1977. Climate and the changing sun. Climatic Change, 1, 173-190. Parker, B. C. and Zeller, E. J. 1980. Nitrogenous chemical composition of antarctic ice and snow. Antarctic Journal of the U.S., 14(5), 80-82. Parker, B. C., Zeller, E. J., Harrower, K., and Thompson, W. J . 1978. Fixed nitrogen in antarctic ice and snow. Antarctic Journal of the U.S., 13(4), 47-48.
1980 REvIEw
Parker, B. C., Zeller, E. J. , Heiskell, L. E., and Thompson, W. J . 1977. Nitrogenous chemical composition of south polar ice and snow as a potential tool for measurement of past solar, auroral, and cosmic ray activities. Antarctic Journal of the U.S., 12(4), 133-134. Parker, B. C., Zeller, E. J., Heiskell, L. E., and Thompson, W. J. 1978. Non-biogenic fixed nitrogen in Antarctica and some ecological implications. Nature, 271, 651-652. (a) Parker, B. C., Zeller, E. J . , Heiskell, L. E., and Thompson, W. J . 1978. Non-biogenic fixed nitrogen in antarctic surface waters. Nature, 276, 96-97. (b) Parker, B. C., Zeller, E. J. , Heiskell, L. E., and Thompson, W. J . In preparation. Oscillations on nitrate and ammonium ion concentrations in South Pole snow for the last millenium. Rood, R. T., Sarazin, C. I., Zeller, E. J., and Parker, B. C. 1979. X- or -y-rays from supernovae in glacial ice. Nature, 382, 701-703. Wilson, A. T., and House, D. A. 1965. Fixation of nitrogen by aurora and its contribution to the nitrogen balance of the earth. Nature, 205,793-794. Zeller, E. J., and Parker, B. C. 1979. Solar activity records. Planetary ice caps. Proceedings for the Second Colloquium on Planetary Water and Polar Processes. Hanover, New Hampshire, 16-18 October 1978. U.S. Army Cold Regions Research and Engineering Laboratory.
81
Nitrogenous chemical composition of antarctic Ice and snow
Figure 3. Predominantly iron spherule, probably a product of atmospheric ablation of a sporadic meteoroid. Background is nucleopore filter paper, magnification 9,800X.
University of Kansas Space Technology Center Lawrence, Kansas 66045
Earlier (Parker and Zeller 1980) we summarized our analytical data, showing that short-term and long-term fluctuations in N0 and NH occur not only in South Pole snow and firn, but in snow and snowpit samples from locations in Antarctica and in Dome C firn core material. Mean value ranges differed from one location to the next, and winter and summer snows showed variation in NO , suggesting a seasonal fallout of N0 during spring. We also listed 12 possible origins of fixed nitrogen, estimating the probability of each being a source for the antarctic ice sheet. In situ N0 and NH production, core contamination, and NO production by lightning were three sources essentially ruled out; denitrification of soils, global anthropogenic and pollutional sources, and volcanic activity (for NH )—all with atmospheric transport—were considered unlikely as major sources as was photochemical NO production.
Our objectives include an understanding of (1) the nitrogenous chemical content of snow and ice of different ages and from different geographic locations, (2) their concentration ranges and periodic and nonperiodic fluctuations, and, as far as possible, (3) their sources and the mechanisms that cause these fluctuations. Details of the above and some of our data, especially concerning fluctuations in the concentrations of nitrate (NO) and ammonium ions (NH+4 ) in a South Pole firn core and snow from other sites in Antarctica have been discusssed previously (Parker and Zeller 1980; Parker, Zeller, Harrower, and Thompson 1978; Parker, Zeller, Heiskell, and Thompson 1977, 1978a, 1978b; Zeller and Parker 1979).
With respect to the remaining potential sources listed, N0 production by meteoroids or by X- and fly-rays from supernovas were considered possible. Rood, Sarazin, Zeller, and Parker (1979) have elaborated on the supernova possibility. Also, we have detected NO 3-concentration peaks at 51, 54, and 100 meters in a 1978-79 110-meter South Pole firn core which come close to the 1974 firn core N0 spikes suggested by Rood, etal. (1979), and which may relate to the supernovas SN 1604 (Kepler), SN 1572 (Tycho) and SN 1181. The NO spike at 83 meters (around 1300 A.D.), for which Rood et al. (1978) found no record of a supernova, is absent from our 1978-79 firn core. However, we find a number of other spikes, probably due to the use of higher resolution analytical techniques.
B. C. PARKER
Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 E. J . ZELLER
1980 REVIEW
79
Finally, we have suggested solar-activity-induced fixation by auroras and/or marine aerosols as probable major sources or mechanisms for the apparent 10-11 and 20-22 year periodicity in NO fluctuations in antarctic snow and firm (Parker and Zeller 1980; Parker et al. 1978a; Zeller and Parker 1979). Solar-induced aurora! NO (and NOT) production with fallout in antarctic snow was first suggested by Wilson and House (1965); however, this mechanism has not been accepted by many who claim a 12th possible source on our list, namely production of N0 by galactic cosmic rays (Bauer 1978; Parker, et al. 1978b). We shall address this controversy in more detail. The figure shows a computer plot of NO (as micrograms of nitrogen per square decimeter per year) from our 1979-80 snowpit samples and the annual sunspot numbers. These values are means of several samples. In all previous publications we have presented our data in micrograms of nitrogen per liter (parts per billion). However, we have noted that the annual snow accumulation at the South Pole usually reaches a maximum at approximately the time when solar activity is highest. Because one can see the annual layers, as well as seasonal layers, and measure their mean thicknesses in snowpits, one can calculate the approximate concentration of a chemical constituent per area per year. The figure shows that maximum NO fallout occurred about 2 years following the two last sunspot maxima, which coincides rather well with the aurora! maxima. In contrast, lowest N0 occurred during periods of low solar activity when maximum galactic cosmic ray fluxes penetrate the Earth's atmosphere. These data cannot be accepted as a generalization until they are repeated extensively at several locations to eliminate chance occurrences. We plan to do so at South Pole in deeper pits, including the last five or more solar maxima. If we can repeat the findings shown in the figure, we shall have support for the major
source of NO in antarctic snow, firn, and ice being solaractivity-induced auroras, and not galactic cosmic rays. From the same 1979-80 snowpit, seasonal sampling for 1962 showed that NO (in micrograms of nitrogen per square decimeter) was higher during July-October than other seasons, the lowest being November-December. This finding confirms our earlier observation (Parker and Zeller 1980) and agrees with earlier arguments (Parker et al. 1978b) that photodestruction of NO,, does not occur in polar regions during winter darkness. However, these observations must be repeated many times at several locations to confirm this as a valid generalization. Sodium (NA) and magnesium analysis by atomic absorbtion spectroscopy did not show a strong correlation with the higher NO NO-3 -3 values. This suggests that marine aerosols probably do not contribute a significant proportion to the NO concentration fluctuations observed. Moreover, in a 1978-79 110-meter South Pole firn core, our lowest NO and highest Nit values occurred within the same interval of 34- to 39-meter depth. Whether this interval, and that proceeding deeper to 42 meters, also with lower NO levels, could be the interval of the "Little Ice Age" or "Maunder Minimum" in solar activity when sunspots and auroras were reduced (Eddy 1977), we cannot positively confirm. However, the frequent high Na levels during the period of about 50 years that this 34- to 39-meter layer was deposited suggests a higher frequency of marine storms over the south polar cap. Plasma emission analysis of select pooled samples for Al, an element of crustal origin, also shows higher than normal levels at South Pole in the 34- to 39-meter low NOR, high Na firn core section. We hope to have a more precise date for various depths of two 1979-80 South Pole firn cores (32 and 43 meters) in which Anthony Cow (Cold Regions Research Engineering Laboratory) has
30 W '-
H
25
-J C/) E
< 20 CD 0 Ci
Z 0 H
Iz W
15
10 5
0 C-)
1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 197 1978 APPROXIMATE YEARS BY SNOW STRATIGRAPHY
80
Sunspot activity curve (diamonds) superimposed on curve of nitrate, per square decimeter, 1919410 snowpit, South Pole Station.
ANmRcTIc JOURNAL
measured the annual layers. We also may be able to detect annual layers in 101- and 57-meter Vostok firn cores collected in 1979-80, now stored and awaiting analysis at Virginia Polytechnic Institute and State University. Detailed findings will be reported later (Parker et al. in preparation). This research was supported by National Science Foundation grant DPI' 78-21417. William Thompson, Lawson Baily, Calvin Glattfelder, and Lawrence Heiskell provided field and laboratory assistance. Anthony Cow and James Cragin gave advice and expert assistance on our future research aims. References Bauer, E. 1978. Non-biogenic fixed nitrogen in antarctic surface waters. Nature, 276, %-97. Eddy, J. A. 1977. Climate and the changing sun. Climatic Change, 1, 173-190. Parker, B. C. and Zeller, E. J. 1980. Nitrogenous chemical composition of antarctic ice and snow. Antarctic Journal of the U.S., 14(5), 80-82. Parker, B. C., Zeller, E. J., Harrower, K., and Thompson, W. J . 1978. Fixed nitrogen in antarctic ice and snow. Antarctic Journal of the U.S., 13(4), 47-48.
1980 REvIEw
Parker, B. C., Zeller, E. J. , Heiskell, L. E., and Thompson, W. J . 1977. Nitrogenous chemical composition of south polar ice and snow as a potential tool for measurement of past solar, auroral, and cosmic ray activities. Antarctic Journal of the U.S., 12(4), 133-134. Parker, B. C., Zeller, E. J., Heiskell, L. E., and Thompson, W. J. 1978. Non-biogenic fixed nitrogen in Antarctica and some ecological implications. Nature, 271, 651-652. (a) Parker, B. C., Zeller, E. J . , Heiskell, L. E., and Thompson, W. J . 1978. Non-biogenic fixed nitrogen in antarctic surface waters. Nature, 276, 96-97. (b) Parker, B. C., Zeller, E. J. , Heiskell, L. E., and Thompson, W. J . In preparation. Oscillations on nitrate and ammonium ion concentrations in South Pole snow for the last millenium. Rood, R. T., Sarazin, C. I., Zeller, E. J., and Parker, B. C. 1979. X- or -y-rays from supernovae in glacial ice. Nature, 382, 701-703. Wilson, A. T., and House, D. A. 1965. Fixation of nitrogen by aurora and its contribution to the nitrogen balance of the earth. Nature, 205,793-794. Zeller, E. J., and Parker, B. C. 1979. Solar activity records. Planetary ice caps. Proceedings for the Second Colloquium on Planetary Water and Polar Processes. Hanover, New Hampshire, 16-18 October 1978. U.S. Army Cold Regions Research and Engineering Laboratory.
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