Fixed nitrogen in antarctic ice and snow amazonaws com
A fact of great interest in the discussion of the age of striations is the occurrence of such beneath volcanic sediments (hyaloclastite) at Boyer Butte. The sediment has been dated by the K/Ar (potassium/argon) method to 13±2 million years (LeMasurier and Rex, 1977); therefore the striations are at least of this age. The striations now uncovered by weathering are very fresh looking. Striations of a similar age have been reported from Jones Mountains (Rutford et al., 1972). According to our preliminary interpretation of the field observations, glaciers in direct contact with the sea have retreated through calving (Hollin, 1962; Hughes, 1973). Glaciers not in direct contact with the sea show no evidence of a retreat in recent time. The lack of evidence for glacier retreat might be a result of extremely fast weathering. The weathering features observed could also be of old age and have survived later expansions because the ice was coldbased. However, we believe overriding ice would erode the substratum, because we frequently observed dirt-bands in the ice at McDonald Heights, at the volcanos, and in the inland ice. Because our field area is located just north of a local ice dome (over 2,000 meters high), which is separated from the main high plateau of the West Antarctic ice sheet, this study does not provide a test of theories about the stability of the ice sheet discussed by Hughes (1973), Whillans (1973, 1976), and Thomas (1976).
This work was supported in part by National Science Foundation grant DPP 76-24209 to the University of Maine.
References
Hollin, J . P. 1962. On the glacial history of Antarctica. Journal of Glaciology, 4: 173-195. Hughes, T. 1973. Is the West Antarctic ice sheet disintegrating?Journal of Geophysical Research, 78: 7887-7910. Le Masurier, W., and D. C. Rex. 1977. Volcanic record of glacial history in Marie Byrd Land and Western Ellsworth Land: Revised chronology and evaluation of tectonic interrelationships. Preliminary draft for the SCAR-meeting in Madison, Wisconsin 1977. Rutford, it, C. Craddock, C. White, and it Armstrong. 1972. Tertiary glaciations in the Jones Mountains. In: Antarctic Geology and Geophysics (RJ. Adie, ed.). Universitetsforlaget, Oslo. pp. 239-243. Thomas, R. H. 1976. Thickening of the Ross Ice Shelf and equilibrium state of the West Antarctic ice sheet. Nature 259 (5540): 180-183. Whillans, I. M. 1973. State of equilibrium of the West Antarctic ice sheet. Science, 182: 476-479. Whillans, I. M. 1976. Radio-echo layers and the recent stability of the West Antarctic ice sheet. Nature 264 (5582): 152-155.
Ice sheet, shelves, glaciers, bergs Fixed nitrogen in antarctic ice and snow BRUCE C. PARKER Department of Biology Virginia Polytechnic Institute and Stale University Blacksburg, Virginia 24061 EDWARD J . ZELLER and KAREN HARROWER Department of Geology University of Kansas Lawrence, Kansas 66044 WILLIAM J . THOMPSON Department of Biology Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061
For about 1 year, we have been examining the concentrations of nitrate (NO nitrite (NO 2 -) and ammonium
0,
October 1978
(NH 4 + ) ions in antarctic ice and snow. We have completed several thousand analyses and are continuing to test the model shown in the figure to identify the source(s) of these ions. We will give a more complete report of our data and interpretations elsewhere; in this article we summarize progress beyond that already published (Parker et al., 1977, 1978). Using portions of a 100-meter South Pole urn core and snow pit samples, we have identified both a short term and long term cyclicity in the concentrations of NO 3-and NH . The presence of significant NH4+ and absence of detectable NO 2 -in clean antarctic firn, ice, and snow had not been previously reported (Wilson and House, 1965). On the basis of estimates of recent average annual snow accumulation at South Pole by numerous glaciologists, we can recognize several climatic maximums and minimums in the South Pole core. These include the Modern Maximum (1900 AD—present), Maunder Minimum (1645-1715 A.D.), Spörer Minimum (1460-1550 A.D.), and part of the Medieval Maximum (1100-1250 A.D.). Climatic minimums apparently correspond to low NO 3-and NH 4 + levels generally. This phenomenon is more pronounced for the Maunder Minimum than for the Spörer Minimum, which is consistent with carbon-14 tree ring data analysis (from Damon, 1968). Power spectrum analysis of data from a South Pole snow pit spanning the period 1925-1977 on a year-by-year basis reveals that NH4+ is not very different from NO 3 in the periodic fluctuations in concentration. Prominent peaks occur at 10.7 and 13.7 years, the first periodicity corresponding
47
rather well with the 10.7-year average value for sun spot (solar flare) peaks (our calculation).
SOLAR FLARES GALACTIC COSMIC RAYS
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 US., 12: 133-134. Parker, B. C., E.J. Zeller, L. E. Heiskell, and W.J. Thompson. 1978. Nonbiogenic fixed nitrogen in Antarctica and some ecological implications. Nature, 271: 651-652. Wilson, A. T., and D. A. House. 1965. Fixation of nitrogen by aurora and its contribution to the nitrogen balance of the Earth. Nature, 205: 793-794.
AURORAS PHOTOCHEMICAL
Ultrasonic measurements on deep ice cores from Antarctica
/NHLX,NOX NOX+NHXIORG_NIVOLCANIC
N
NOx, (? NHx)
V
TERRESTRIAL (MICROBIAL) NOx ,NHx ,ORGN
OCEANIC MARINE AEROSOLS NtJx ,NHx ,ORGN
SNOW Word model showing various hypothetical sources of fixed nitrogen to snow and glacial ice. A Vostok ice core specimen approximately 10,000 years old revealed the highest NO 3 - concentration of 525 micrograms of NO 3 -Nper liter, while surface snow at Vostok Station showed about the same levels of NO 3 - and NH4+ found at South Pole. Microorganisms and in situ microbial activity at South Pole have been ruled out as possible contributors to the NO3 and NH 4 + in the snow and firn. Pollution also has been ruled out. We are currently testing other potential sources (see figure). Regardless of the source, it is apparent that antarctic snow, firn, and ice possess a long term and short term record, reflected in the NO 3-and NH 4 + concentrations, which seems to indicate past trends in global climate. This research promises to add yet another tool to the use of glacial ice in studying climatic events prior to, into, and following the last major glaciation, and may provide information of value in long term climate prediction. We are grateful to the Office of Naval Research for a contract supporting these studies and to the National Science Foundation for logistics support, and approval of the use of the South Pole core, as available, from C. Langway at the State University of New York, Buffalo, New York.
References
Damon, P. E. 1968. Radiocarbon and climate. Meterological Monographs, 8: 151-153. Parker, B. C., E.J. Zeller, L. E. Heiskell, and W.J. Thompson. 1977. 48
ANTHONY J .
Gow
US. Army Cold Regions Research and Engineering Laboratory Hanover, New Hampshire 03755 HEINZ KOHNEN
Inst it utefür Geophysik der Westfalisc/ien Wilhelms Universitd t Munster, West Germany
The importance of crystal anisotropy (oriented crystal structure) in determining the rheological behavior of polar ice sheets can no longer be ignored, especially in light of recent observations of widespread crystal anisotropy in West Antarctica (Bentley, 1971; Gow and Williamson, 1976). This report discusses some results of recent measurements of ultrasonic velocities performed on ice cores collected in 1968 at Byrd Station. This sonic logging of cores in a sense amplifies and extends the original bore hole logging of Bentley (1972). However, Bentley's measurements were restricted to P-wave velocity determinations along the bore hole axis, whereas our measurements were made in the diametral (transverse) direction (Vp—. ) as well as along the vertical axis (V1), which corresponds to the bore hole axis. This dual velocity measurement permits immediate evaluation of the velocity difference (V), a very important parameter whose magnitude depends entirely on the orientation of crystals in the ice core. Our objectives were to determine the functional relationship between ultrasonic velocities and the c-axis fabrics, and to evaluate the relaxation characteristics of the drilled cores, especially the directional aspects of relaxation. Because cores have relaxed appreciably since 1968, densities of the cores must be remeasured simultaneously with the velocity measurements before corrections to the velocity data can be made to correspond with in situ temperatures and densities. These remeasurements also provide an independent source of data on the relaxation characteristics of deep ice cores. Ultrasonic measurements also were performed on cores from the original Ross Ice Shelf drilling at Little America V (1958-1959).
ANTARCTIC JOURNAL
This work was supported in part by National Science Foundation grant DPP 76-24209 to the University of Maine.
References
Hollin, J . P. 1962. On the glacial history of Antarctica. Journal of Glaciology, 4: 173-195. Hughes, T. 1973. Is the West Antarctic ice sheet disintegrating?Journal of Geophysical Research, 78: 7887-7910. Le Masurier, W., and D. C. Rex. 1977. Volcanic record of glacial history in Marie Byrd Land and Western Ellsworth Land: Revised chronology and evaluation of tectonic interrelationships. Preliminary draft for the SCAR-meeting in Madison, Wisconsin 1977. Rutford, it, C. Craddock, C. White, and it Armstrong. 1972. Tertiary glaciations in the Jones Mountains. In: Antarctic Geology and Geophysics (RJ. Adie, ed.). Universitetsforlaget, Oslo. pp. 239-243. Thomas, R. H. 1976. Thickening of the Ross Ice Shelf and equilibrium state of the West Antarctic ice sheet. Nature 259 (5540): 180-183. Whillans, I. M. 1973. State of equilibrium of the West Antarctic ice sheet. Science, 182: 476-479. Whillans, I. M. 1976. Radio-echo layers and the recent stability of the West Antarctic ice sheet. Nature 264 (5582): 152-155.
Ice sheet, shelves, glaciers, bergs Fixed nitrogen in antarctic ice and snow BRUCE C. PARKER Department of Biology Virginia Polytechnic Institute and Stale University Blacksburg, Virginia 24061 EDWARD J . ZELLER and KAREN HARROWER Department of Geology University of Kansas Lawrence, Kansas 66044 WILLIAM J . THOMPSON Department of Biology Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061
For about 1 year, we have been examining the concentrations of nitrate (NO nitrite (NO 2 -) and ammonium
0,
October 1978
(NH 4 + ) ions in antarctic ice and snow. We have completed several thousand analyses and are continuing to test the model shown in the figure to identify the source(s) of these ions. We will give a more complete report of our data and interpretations elsewhere; in this article we summarize progress beyond that already published (Parker et al., 1977, 1978). Using portions of a 100-meter South Pole urn core and snow pit samples, we have identified both a short term and long term cyclicity in the concentrations of NO 3-and NH . The presence of significant NH4+ and absence of detectable NO 2 -in clean antarctic firn, ice, and snow had not been previously reported (Wilson and House, 1965). On the basis of estimates of recent average annual snow accumulation at South Pole by numerous glaciologists, we can recognize several climatic maximums and minimums in the South Pole core. These include the Modern Maximum (1900 AD—present), Maunder Minimum (1645-1715 A.D.), Spörer Minimum (1460-1550 A.D.), and part of the Medieval Maximum (1100-1250 A.D.). Climatic minimums apparently correspond to low NO 3-and NH 4 + levels generally. This phenomenon is more pronounced for the Maunder Minimum than for the Spörer Minimum, which is consistent with carbon-14 tree ring data analysis (from Damon, 1968). Power spectrum analysis of data from a South Pole snow pit spanning the period 1925-1977 on a year-by-year basis reveals that NH4+ is not very different from NO 3 in the periodic fluctuations in concentration. Prominent peaks occur at 10.7 and 13.7 years, the first periodicity corresponding
47
rather well with the 10.7-year average value for sun spot (solar flare) peaks (our calculation).
SOLAR FLARES GALACTIC COSMIC RAYS
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 US., 12: 133-134. Parker, B. C., E.J. Zeller, L. E. Heiskell, and W.J. Thompson. 1978. Nonbiogenic fixed nitrogen in Antarctica and some ecological implications. Nature, 271: 651-652. Wilson, A. T., and D. A. House. 1965. Fixation of nitrogen by aurora and its contribution to the nitrogen balance of the Earth. Nature, 205: 793-794.
AURORAS PHOTOCHEMICAL
Ultrasonic measurements on deep ice cores from Antarctica
/NHLX,NOX NOX+NHXIORG_NIVOLCANIC
N
NOx, (? NHx)
V
TERRESTRIAL (MICROBIAL) NOx ,NHx ,ORGN
OCEANIC MARINE AEROSOLS NtJx ,NHx ,ORGN
SNOW Word model showing various hypothetical sources of fixed nitrogen to snow and glacial ice. A Vostok ice core specimen approximately 10,000 years old revealed the highest NO 3 - concentration of 525 micrograms of NO 3 -Nper liter, while surface snow at Vostok Station showed about the same levels of NO 3 - and NH4+ found at South Pole. Microorganisms and in situ microbial activity at South Pole have been ruled out as possible contributors to the NO3 and NH 4 + in the snow and firn. Pollution also has been ruled out. We are currently testing other potential sources (see figure). Regardless of the source, it is apparent that antarctic snow, firn, and ice possess a long term and short term record, reflected in the NO 3-and NH 4 + concentrations, which seems to indicate past trends in global climate. This research promises to add yet another tool to the use of glacial ice in studying climatic events prior to, into, and following the last major glaciation, and may provide information of value in long term climate prediction. We are grateful to the Office of Naval Research for a contract supporting these studies and to the National Science Foundation for logistics support, and approval of the use of the South Pole core, as available, from C. Langway at the State University of New York, Buffalo, New York.
References
Damon, P. E. 1968. Radiocarbon and climate. Meterological Monographs, 8: 151-153. Parker, B. C., E.J. Zeller, L. E. Heiskell, and W.J. Thompson. 1977. 48
ANTHONY J .
Gow
US. Army Cold Regions Research and Engineering Laboratory Hanover, New Hampshire 03755 HEINZ KOHNEN
Inst it utefür Geophysik der Westfalisc/ien Wilhelms Universitd t Munster, West Germany
The importance of crystal anisotropy (oriented crystal structure) in determining the rheological behavior of polar ice sheets can no longer be ignored, especially in light of recent observations of widespread crystal anisotropy in West Antarctica (Bentley, 1971; Gow and Williamson, 1976). This report discusses some results of recent measurements of ultrasonic velocities performed on ice cores collected in 1968 at Byrd Station. This sonic logging of cores in a sense amplifies and extends the original bore hole logging of Bentley (1972). However, Bentley's measurements were restricted to P-wave velocity determinations along the bore hole axis, whereas our measurements were made in the diametral (transverse) direction (Vp—. ) as well as along the vertical axis (V1), which corresponds to the bore hole axis. This dual velocity measurement permits immediate evaluation of the velocity difference (V), a very important parameter whose magnitude depends entirely on the orientation of crystals in the ice core. Our objectives were to determine the functional relationship between ultrasonic velocities and the c-axis fabrics, and to evaluate the relaxation characteristics of the drilled cores, especially the directional aspects of relaxation. Because cores have relaxed appreciably since 1968, densities of the cores must be remeasured simultaneously with the velocity measurements before corrections to the velocity data can be made to correspond with in situ temperatures and densities. These remeasurements also provide an independent source of data on the relaxation characteristics of deep ice cores. Ultrasonic measurements also were performed on cores from the original Ross Ice Shelf drilling at Little America V (1958-1959).
ANTARCTIC JOURNAL
