Suspended particulate matter in antarctic coastal waters
70
PENINSULA SEDIMENT TRAPS • /
60
C,' CO
Q 40
I'
ca 30
Cj
20 10
I' ()
0 0
/c// 0 0 c0/ •
IA.
00
ROSS SEA SEDIMENT TRAPS
0
0 I_I'A I I I I I 0 1 2 3 4 5 6 7 8 WT. % ORGANIC CARBON Figure 2. Weight percentage ("WT%") organic carbon vs. weight percentage biogenic silica for surface sediments of the Bransfield Strait and Ross Sea and sediment-trap samples from Granite Harbour and the central Ross Sea (squares) and the Bransfield Strait (solid circles).
References Bremner, J.M. 1983. Biogenic sediments on the South West African (Namibian) continental margin. In J. Thiede and E. Suess (Eds.), Coastal upwelling: Its sediment record, Part B. New York: Plenum Press. DeMaster, D.J. 1981. The supply and accumulation of silica in the marine environment. Geochimica et Cosmochimica Acta, 45, 1715-1732.
Suspended particulate matter in antarctic coastal waters A.R. LEVENTER and R.B. DUNBAR Department of Geology Rice University Houston, Texas 77251
Suspended particulate matter plays an important role in maintaining chemical and biological gradients in the ocean. Its composition and concentration reflect dynamic water-column processes such as primary production in surface waters, dissolution and degradation at depth, and vertical and lateral parti100
Donegan, D., and H. Schrader. 1981. Modern analogs of the Miocene diatomaceous Monterey Shale of California: Evidence from sedimentologic and micropaleontologic study. In R.E. Garrison, R.G. Douglas, K.E. Pisciotto, G.M. Isaacs, and J.C. Ingle (Eds.), The Monterey Formation and related siliceous rocks of California. Los Angeles: Society of Economic Paleontologists and Mineralogists, Pacific Section. Dunbar, R.B. 1984. Sediment trap experiments on the Antarctic continental margin. Antarctic Journal of the U.S., 19(5), 70 - 71. Dunbar, R.B., J.B. Anderson, E.W. Domack, and S.S. Jacobs. 1985. Oceanographic influences on sedimentation along the antarctic conti nental shelf. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Shelf (Antarctic Research Series, Vol 43.) Washington, D.C.: American Geophysical Union. Dunbar, R. B., M. Dehn, and A. Leventer. 1984. Distribution of biogenic components in surface sediments from the antarctic continental shelf. Antarctic Journal of the U.S., 19(5), 126 - 128. Dymond, J . , K. Fischer, M. Clauson, R. Cobler, W. Gardner, M.J. Richardson, W. Berger, A. Soutar, and R. Dunbar. 1981. A sediment trap intercomparison study in the Santa Barbara Basin. Earth and Planetary Science Letters, 53, 409 - 418. Futterer, D., and scientific crew (ANTARKTIS-I1). 1984. Report on polar research. Bremerhaven: Alfred-Wegener-Institut für Polarforschung. (In German.)
Pyne, A. 1984. Immediate report, Victoria University of Wellington Antarctic expedition 28, 1983 - 1984. Wellington: Antarctic Re-
search Centre, Victoria University. Reimers, C.E., and E. Suess. 1983. Spatial and temporal patterns of organic matter accumulation on the Peru continental margin. In J. Thiede and E. Suess (Eds.), Coastal upwelling: Its sediment record, Part B. New York: Plenum Press. Smith, W.O., and D.M. Nelson. 1985. Phytoplankton bloom produced by a receding ice edge in the Ross Sea: Spatial coherence with the density field. Science, 227, 163 - 166. Suess, E., and A. Ungerer. 1981. Element and phase composition of particulate matter from the circumpolar current between New Zealand and Antarctica. Oceanologica Acta, 4, 151 160. Sullivan, C.W., A.C. Palmisano, S. Kottmeier, and R. Moe. 1982. Development of the sea ice microbial community in McMurdo Sound. Antarctic Journal of the U. S., 17(5), 155- 157. von Bodungen, B. 1984. Personal communication. Zeitschel, B., L. Uhlmann, and P. Diekmann. 1978. A new multisample sediment trap. Marine Biology, 45, 285 - 288.
cle transport (Biscaye and Eittreim 1977; Bishop et al. 1977; Lal and Lerman 1973). Because much of the ocean's bottom water originates on the antarctic margin, variations in particulatematter supply and interaction with the southern-ocean water column may influence global ocean chemistry significantly. Suspended particulate matter was collected by filtration of I to 2 liters of seawater (from Niskin bottle samples) through preweighed 0.4-micrometer Nuclepore membrane filters. Filters were dried in a dessicator and reweighed as soon as possible. Based on processing of "blank" filters, weighing precision for our samples is 20 micrograms. Areas studied include transect parallel to the edge of the Ross Ice Shelf (February 1983, figure 1), McMurdo Sound (October to November 1984, figur 2), and the Antarctic Peninsula region (November and De cember 1983, figure 3). The Ross Ice Shelf and Antarctic Penin sula samples were collected in areas relatively free of sea ice The McMurdo Sound samples were collected from beneat annual fast ice. ANTARCTIC JOURNAL
0
SPM jjg/I 0 500 1000 1500 2000 2500 3000
100 200
Deep Freeze 83
300 400 depth 500 (m) 600 700 800 900 1000 1100
Figure 1. Suspended particulate matter profiles adjacent to the Ross Ice Shelf, February 1983. ("m" denotes "meter." "pgIl" denotes "micrograms per liter.")
Collection and filtration of suspended particles has several advantages over indirect methods employing nephelometers, in which light scattering is measured and particle concentrations are calculated based on a previously derived calibration curve (Gibbs 1974; Biscaye and Eittreim 1977). Through direct filtering, absolute concentrations may be determined. Subsequently, the filtered sample can be analyzed both geochemically and microscopically. Suspended particulate concentrations range from approximately 50 to 3,000 micrograms per liter and usually fall between 50 and 800 micrograms per liter (figures 1 through 3). Elverhoi and Roaldset (1983) measured suspended particle concentrations from 100 to 2,000 micrograms per liter in water samples from the eastern and central Weddell Sea, by filtering through 0.22-micrometer Nuclepore filters. All of the reported antarctic values are significantly lower than suspended particle concentrations observed in glaciomarine environments subject to major influxes of sediment-laden meltwater, where concntrations may be as high as 15,000 micrograms per liter (Bering Sea, Lisitzin 1972). Surface-water particulate concentrations vary widely among the profiles and are greatly influenced by primary production within the photic zone. The highest concentrations, up to 3,000 micrograms per liter, were observed along the Ross Ice Shelf 1985 REVIEW
transect (figure 1). In both McMurdo Sound (figure 2) and the Antarctic Peninsula (figure 3), maximum suspended particulate concentrations in surface waters were less than 800 micrograms per liter. Smith and Nelson (1985) have reported high concentrations of biogenic phases within a phytoplankton bloom associated with a late summer receding ice edge in the Ross Sea. Particle residence times in surface waters of the Ross Sea are high probably because of the low-standing stock of planktonic herbivores (Biggs, Amos, and Holm-Hansen in press). Thus, surface-water particulate concentrations during bloom periods may be maintained at a higher level in the Ross Sea than in the Antarctic Peninsula/Scotia Sea region where zooplankton are effectively filtering and pelletizing bloom products (Dunbar, Anderson, and Leventer 1984). A high particulate concentration was also observed adjacent to the underside of the annual sea ice in McMurdo Sound (site I, figure 2), early during the austral spring, presumably related to the development of the sea-ice microbial community (Sullivan et al. 1982). Concentrations of particulate matter recorded from November and December 1983 in the Antarctic Peninsula area probably do not represent maximum seasonal values. Based on a year-long study at Arthur Harbor (Antarctic Peninsula), Krebs (1983) observed a small spring phytoplankton bloom in November, followed by a much larger summer bloom in early 101
January and a fall bloom in early March. In figure 3A, the seasonal increase in surface concentrations of particulate matter is demonstrated, with higher surface concentrations occurring in mid-December than in late November.
0
0
&PENDED PARTICULATE MATTER .tig/I 200 400 600 800 200 400 600 800
B•----' 200
200 400
SUSPENDED PARTICULATE MATTER pg/I 0 200 400 600 0 . 200 Dm/ E a.
400-
600
233
1200
2000 3000 4000
1400
5000
•238 •247 225 233 265 .267
1600
78°
- 177, 800 -
1. 162° 166°
Figure 2. Suspended particulate matter profiles from beneath sea ice in McMurdo Sound, October and November 1984. ('rn" denotes "meter." "g/1" denotes "micrograms per liter:')
Concentrations of suspended matter generally decrease with depth, reaching average mid-water values at about 100 meters. Mid-water concentrations adjacent to the Ross Ice Shelf fluctuate between 100 and 500 micrograms per liter (figure 1). Midwater concentrations from the Antarctic Peninsula region decrease to 100 to 200 micrograms per liter (figure 3), the lowest concentrations observed, again reflecting efficient grazing, pelletization, and shorter suspended particle residence time. The Weddell Sea is believed to be a major site of formation of antarctic bottom water (Foster and Carmack 1976). Several of the 1983 profiles of suspended particulate matter in the northwest Weddell Sea (figure 3B) indicate a well developed near-bottom nepheloid layer (sites 233 and 238), possibly related to particle resuspension and transport by newly produced bottom water. However, such a near-bottom increase in particulate concentration is not observed at depths below 3,000 meters (sites 254 and 267). Three of seven profiles taken adjacent to the Ross Ice Shelf (figure 1, sites a, c, d) also display increased concentrations of particulate matter within 50 meters of the bottom. Current-meter and sediment-textural data from the Ross Sea suggest that shelf currents are actively resuspending and transporting fine-grained sediments from depths of up to 500 meters (Dunbar et al. in press). Episodic and variable flow events (Jacobs, Amos, and Bruchhausen 1970) produce nepheloid layers which are ephemeral in nature, and which transport winnowed phases to basins and other low-energy areas of the shelf. We plan to continue our studies by examining the relationship between those particles in rapid vertical transit and those suspended in the water column. We hope this will lead to a better understanding of the factors involved in the modification of particulate matter through dissolution and degradation during descent to the sea floor and through current winnowing and resuspension. This work was supported by National Science Foundation grants DPP 83-12486 and INT 83-14541. 102
I\ I-i
1000
800
•I 770 \McMurdo \SoundO
400
225- 6()0 238 247 11/26/83 800 254 / 271 265-............ 273 12/19-20/83 i000 267
600
•:J
'•-/-. /
271
1800 2000 1. ''
60°
Wedded Sea 254. ZV
60°
500
L55.
Figure 3. A. Suspended particulate matter profiles from the Bransfield Strait, November and December 1983. B. Suspended particulate matter profiles from the northwestern Weddell Sea, November and December 1983. ("m" denotes "meter:' "ig/1" denotes "micrograms per liter:')
References Biggs, D.C., A.F. Amos, and 0. Holm-Hansen. In press. Oceanographic studies of epipelagic ammonium distributions: The Ross Sea NH4 + flux experiment. In W. R. Siegfried (Ed.), Fourth SCAR Symposium Antarctic Biology. New York: Springer-Verlag. Biscaye, P.E., and S.L. Eittreim. 1977. Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean. Marine Geology, 23, 155 - 172. Bishop, J.K.B., J.M. Edmond, P.R. Ketten, M.P. Bacon, and W.B. Silker. 1977. The chemistry, biology, and vertical flux of particulate matter from the upper 400m of the equatorial Atlantic Ocean. Deep-Sea Research, 24, 511 - 548. Dunbar, R.B., J.B. Anderson, and A. Leventer. 1984. Water column fluxes and biogenic sediments of the Ross Sea and Bransfield Strait, Antarctica. Abstracts with Programs, Annual Meeting, Geological Society of America, 16, 496. Dunbar, R.B., J.B. Anderson, E.W. Domack, and S.S. Jacobs. In pres. Oceanographic influences on sedimentation along the Antarctic co ntinental shelf. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Shelf. (Antarctic Research Series.) Washington, D.C.: American Geophysical Union. Elverhoi, A., and E. Roaldset. 1983. Glaciomarine sediments and suispended particulate matter, Weddell Sea Shelf, Antarctica. Polar search, 1 n.s., 1 - 21. Foster, T.D., and E.C. Carmack. 1976. Frontal zone mixing and Antarctic Bottom Water formation in the southern Weddell Sea. Deep-Sea Research, 23, 301 - 317. Gibbs, R.J. 1974. Principles of studying suspended materials in water. In R.J. Gibbs (Ed.), Suspended solids in water. New York: Plenum Press. Jacobs, S.S., A.F. Amos, and P.M. Bruchhausen. 1970. Ross Sea oceanography and Antarctic Bottom Water formation. Deep-Sea Research, 17, 935-962. ANTARCTIC JOURNAL
Krebs, W.N. 1983. Ecology of neritic marine diatoms, Arthur Harbor, Antarctica. Micropaleontology, 29(3), 267 - 297. La!, D., and A. Lerman. 1973. Dissolution and behavior of particulate biogenic matter in the ocean: Some theoretical considerations. Journal of Geophysical Research, 78, 7100 - 7111. Lisitzin, A.P. 1972. Sedimentation in the world ocean. (SEPM Special Publication 17.) Tulsa, Ok.: Society of Economic Paleontologists and Mineralogists.
Smith, W. 0., and D. Nelson. 1985. Phytoplankton bloom produced by receding ice edge in the Ross Sea: Spatial coherence with the density field. Science, 227, 163 - 166. Sullivan, C.W., A.C. Palmisano, S. Kottmeier, and R. Moe. 1982. Development of the sea-ice microbial community in McMurdo Sound. Antarctic Journal of the U.S., 17(5), 155 - 157.
Wilkes Land Expedition 1985
L. Hunt's group at the University of California, Irvine, conducted ornithological research, and David L. Garrison from the University of California, Santa Cruz, conducted biological oceanographic studies. Technical assistance was provided by Timothy J. Fields and James A. Schmitt from Scripps Institution of Oceanography and by the Marine Science Department of the
THEODORE D. FOSTER
Marine Sciences University of California Santa Cruz, California 95064
Polar Star.
50°E
160°E 65°S
650S
The Wilkes Land Expedition 1985 sought to study an almost unexplored region of the southern oceans off Wilkes Land between 147° and 162°E. The scientific party embarked on the U.S. Coast Guard icebreaker Polar Star on 12 February 1985 at McMurdo Station, Antarctica, and disembarked on 9 March 1985 at Wellington, New Zealand. The primary impetus for the expedition was the suggestion of Carmack and Killworth (1978) that this region may be a source of deep water which may be an important contribution to the abyssal waters of the world ocean. Satellite sea-ice observations have shown that this region is nearly always ice-covered even in austral summer; 1985 proved to be no exception. The continental shelf portion of the region was found to be covered with closely packed ice floes. The icebreaking capabilities of the ship limited penetration of the region to the edges of the ice pack. Nevertheless, most of the region was explored. The primary research program's goal was to make a physical and chemical reconnaissance of the potential deep-water formation region. The physical oceanography program was directed by Theodore D. Foster of the University of California, Santa Cruz, and included participation by Miao Yutian, a scientific observer from the Second Institute of Oceanography of the People's Republic of China, and Eric C. Eckert of the University of California, Santa Cruz. The chemical oceanography program was under the direction of Robert L. Michel of Scripps Institution of Oceanography and included participation by Roy A. Schroeder of the United States Geological Survey, Robin S. Keir of Scripps Institution of Oceanography, and Frederick A. Van Woy from Ray F. Weiss' group at Scripps Institution of Oceanography. In addition to the investigation of deep-water formation, Nancy M. Harrison and Zoe A. Eppley from George
195 REVIEW
70°S
50E
1600E
700 S
Track of Polar Star and positions of hydrographic stations during Wilkes Land Expedition 1985.
The figure shows the cruise track of Polar Star in the potential deep-water formation region off Wilkes Land. A total of 86 hydrographic stations were occupied in this region. In addition, two test stations were occupied proceeding to the area, and five hydrographic stations were attempted on the transit to Wellington. Winch failure and inability of Polar Star to carry out satisfactory open-water hydrographic work, as well as a shortened cruise, prevented completion of this section. Reference Carmack, E. C., and P.D. Killworth. 1978. Formation and interleaving of abyssal water masses off Wilkes Land, Antarctica. Deep-Sea Research, 25, 357 - 369.
103
PENINSULA SEDIMENT TRAPS • /
60
C,' CO
Q 40
I'
ca 30
Cj
20 10
I' ()
0 0
/c// 0 0 c0/ •
IA.
00
ROSS SEA SEDIMENT TRAPS
0
0 I_I'A I I I I I 0 1 2 3 4 5 6 7 8 WT. % ORGANIC CARBON Figure 2. Weight percentage ("WT%") organic carbon vs. weight percentage biogenic silica for surface sediments of the Bransfield Strait and Ross Sea and sediment-trap samples from Granite Harbour and the central Ross Sea (squares) and the Bransfield Strait (solid circles).
References Bremner, J.M. 1983. Biogenic sediments on the South West African (Namibian) continental margin. In J. Thiede and E. Suess (Eds.), Coastal upwelling: Its sediment record, Part B. New York: Plenum Press. DeMaster, D.J. 1981. The supply and accumulation of silica in the marine environment. Geochimica et Cosmochimica Acta, 45, 1715-1732.
Suspended particulate matter in antarctic coastal waters A.R. LEVENTER and R.B. DUNBAR Department of Geology Rice University Houston, Texas 77251
Suspended particulate matter plays an important role in maintaining chemical and biological gradients in the ocean. Its composition and concentration reflect dynamic water-column processes such as primary production in surface waters, dissolution and degradation at depth, and vertical and lateral parti100
Donegan, D., and H. Schrader. 1981. Modern analogs of the Miocene diatomaceous Monterey Shale of California: Evidence from sedimentologic and micropaleontologic study. In R.E. Garrison, R.G. Douglas, K.E. Pisciotto, G.M. Isaacs, and J.C. Ingle (Eds.), The Monterey Formation and related siliceous rocks of California. Los Angeles: Society of Economic Paleontologists and Mineralogists, Pacific Section. Dunbar, R.B. 1984. Sediment trap experiments on the Antarctic continental margin. Antarctic Journal of the U.S., 19(5), 70 - 71. Dunbar, R.B., J.B. Anderson, E.W. Domack, and S.S. Jacobs. 1985. Oceanographic influences on sedimentation along the antarctic conti nental shelf. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Shelf (Antarctic Research Series, Vol 43.) Washington, D.C.: American Geophysical Union. Dunbar, R. B., M. Dehn, and A. Leventer. 1984. Distribution of biogenic components in surface sediments from the antarctic continental shelf. Antarctic Journal of the U.S., 19(5), 126 - 128. Dymond, J . , K. Fischer, M. Clauson, R. Cobler, W. Gardner, M.J. Richardson, W. Berger, A. Soutar, and R. Dunbar. 1981. A sediment trap intercomparison study in the Santa Barbara Basin. Earth and Planetary Science Letters, 53, 409 - 418. Futterer, D., and scientific crew (ANTARKTIS-I1). 1984. Report on polar research. Bremerhaven: Alfred-Wegener-Institut für Polarforschung. (In German.)
Pyne, A. 1984. Immediate report, Victoria University of Wellington Antarctic expedition 28, 1983 - 1984. Wellington: Antarctic Re-
search Centre, Victoria University. Reimers, C.E., and E. Suess. 1983. Spatial and temporal patterns of organic matter accumulation on the Peru continental margin. In J. Thiede and E. Suess (Eds.), Coastal upwelling: Its sediment record, Part B. New York: Plenum Press. Smith, W.O., and D.M. Nelson. 1985. Phytoplankton bloom produced by a receding ice edge in the Ross Sea: Spatial coherence with the density field. Science, 227, 163 - 166. Suess, E., and A. Ungerer. 1981. Element and phase composition of particulate matter from the circumpolar current between New Zealand and Antarctica. Oceanologica Acta, 4, 151 160. Sullivan, C.W., A.C. Palmisano, S. Kottmeier, and R. Moe. 1982. Development of the sea ice microbial community in McMurdo Sound. Antarctic Journal of the U. S., 17(5), 155- 157. von Bodungen, B. 1984. Personal communication. Zeitschel, B., L. Uhlmann, and P. Diekmann. 1978. A new multisample sediment trap. Marine Biology, 45, 285 - 288.
cle transport (Biscaye and Eittreim 1977; Bishop et al. 1977; Lal and Lerman 1973). Because much of the ocean's bottom water originates on the antarctic margin, variations in particulatematter supply and interaction with the southern-ocean water column may influence global ocean chemistry significantly. Suspended particulate matter was collected by filtration of I to 2 liters of seawater (from Niskin bottle samples) through preweighed 0.4-micrometer Nuclepore membrane filters. Filters were dried in a dessicator and reweighed as soon as possible. Based on processing of "blank" filters, weighing precision for our samples is 20 micrograms. Areas studied include transect parallel to the edge of the Ross Ice Shelf (February 1983, figure 1), McMurdo Sound (October to November 1984, figur 2), and the Antarctic Peninsula region (November and De cember 1983, figure 3). The Ross Ice Shelf and Antarctic Penin sula samples were collected in areas relatively free of sea ice The McMurdo Sound samples were collected from beneat annual fast ice. ANTARCTIC JOURNAL
0
SPM jjg/I 0 500 1000 1500 2000 2500 3000
100 200
Deep Freeze 83
300 400 depth 500 (m) 600 700 800 900 1000 1100
Figure 1. Suspended particulate matter profiles adjacent to the Ross Ice Shelf, February 1983. ("m" denotes "meter." "pgIl" denotes "micrograms per liter.")
Collection and filtration of suspended particles has several advantages over indirect methods employing nephelometers, in which light scattering is measured and particle concentrations are calculated based on a previously derived calibration curve (Gibbs 1974; Biscaye and Eittreim 1977). Through direct filtering, absolute concentrations may be determined. Subsequently, the filtered sample can be analyzed both geochemically and microscopically. Suspended particulate concentrations range from approximately 50 to 3,000 micrograms per liter and usually fall between 50 and 800 micrograms per liter (figures 1 through 3). Elverhoi and Roaldset (1983) measured suspended particle concentrations from 100 to 2,000 micrograms per liter in water samples from the eastern and central Weddell Sea, by filtering through 0.22-micrometer Nuclepore filters. All of the reported antarctic values are significantly lower than suspended particle concentrations observed in glaciomarine environments subject to major influxes of sediment-laden meltwater, where concntrations may be as high as 15,000 micrograms per liter (Bering Sea, Lisitzin 1972). Surface-water particulate concentrations vary widely among the profiles and are greatly influenced by primary production within the photic zone. The highest concentrations, up to 3,000 micrograms per liter, were observed along the Ross Ice Shelf 1985 REVIEW
transect (figure 1). In both McMurdo Sound (figure 2) and the Antarctic Peninsula (figure 3), maximum suspended particulate concentrations in surface waters were less than 800 micrograms per liter. Smith and Nelson (1985) have reported high concentrations of biogenic phases within a phytoplankton bloom associated with a late summer receding ice edge in the Ross Sea. Particle residence times in surface waters of the Ross Sea are high probably because of the low-standing stock of planktonic herbivores (Biggs, Amos, and Holm-Hansen in press). Thus, surface-water particulate concentrations during bloom periods may be maintained at a higher level in the Ross Sea than in the Antarctic Peninsula/Scotia Sea region where zooplankton are effectively filtering and pelletizing bloom products (Dunbar, Anderson, and Leventer 1984). A high particulate concentration was also observed adjacent to the underside of the annual sea ice in McMurdo Sound (site I, figure 2), early during the austral spring, presumably related to the development of the sea-ice microbial community (Sullivan et al. 1982). Concentrations of particulate matter recorded from November and December 1983 in the Antarctic Peninsula area probably do not represent maximum seasonal values. Based on a year-long study at Arthur Harbor (Antarctic Peninsula), Krebs (1983) observed a small spring phytoplankton bloom in November, followed by a much larger summer bloom in early 101
January and a fall bloom in early March. In figure 3A, the seasonal increase in surface concentrations of particulate matter is demonstrated, with higher surface concentrations occurring in mid-December than in late November.
0
0
&PENDED PARTICULATE MATTER .tig/I 200 400 600 800 200 400 600 800
B•----' 200
200 400
SUSPENDED PARTICULATE MATTER pg/I 0 200 400 600 0 . 200 Dm/ E a.
400-
600
233
1200
2000 3000 4000
1400
5000
•238 •247 225 233 265 .267
1600
78°
- 177, 800 -
1. 162° 166°
Figure 2. Suspended particulate matter profiles from beneath sea ice in McMurdo Sound, October and November 1984. ('rn" denotes "meter." "g/1" denotes "micrograms per liter:')
Concentrations of suspended matter generally decrease with depth, reaching average mid-water values at about 100 meters. Mid-water concentrations adjacent to the Ross Ice Shelf fluctuate between 100 and 500 micrograms per liter (figure 1). Midwater concentrations from the Antarctic Peninsula region decrease to 100 to 200 micrograms per liter (figure 3), the lowest concentrations observed, again reflecting efficient grazing, pelletization, and shorter suspended particle residence time. The Weddell Sea is believed to be a major site of formation of antarctic bottom water (Foster and Carmack 1976). Several of the 1983 profiles of suspended particulate matter in the northwest Weddell Sea (figure 3B) indicate a well developed near-bottom nepheloid layer (sites 233 and 238), possibly related to particle resuspension and transport by newly produced bottom water. However, such a near-bottom increase in particulate concentration is not observed at depths below 3,000 meters (sites 254 and 267). Three of seven profiles taken adjacent to the Ross Ice Shelf (figure 1, sites a, c, d) also display increased concentrations of particulate matter within 50 meters of the bottom. Current-meter and sediment-textural data from the Ross Sea suggest that shelf currents are actively resuspending and transporting fine-grained sediments from depths of up to 500 meters (Dunbar et al. in press). Episodic and variable flow events (Jacobs, Amos, and Bruchhausen 1970) produce nepheloid layers which are ephemeral in nature, and which transport winnowed phases to basins and other low-energy areas of the shelf. We plan to continue our studies by examining the relationship between those particles in rapid vertical transit and those suspended in the water column. We hope this will lead to a better understanding of the factors involved in the modification of particulate matter through dissolution and degradation during descent to the sea floor and through current winnowing and resuspension. This work was supported by National Science Foundation grants DPP 83-12486 and INT 83-14541. 102
I\ I-i
1000
800
•I 770 \McMurdo \SoundO
400
225- 6()0 238 247 11/26/83 800 254 / 271 265-............ 273 12/19-20/83 i000 267
600
•:J
'•-/-. /
271
1800 2000 1. ''
60°
Wedded Sea 254. ZV
60°
500
L55.
Figure 3. A. Suspended particulate matter profiles from the Bransfield Strait, November and December 1983. B. Suspended particulate matter profiles from the northwestern Weddell Sea, November and December 1983. ("m" denotes "meter:' "ig/1" denotes "micrograms per liter:')
References Biggs, D.C., A.F. Amos, and 0. Holm-Hansen. In press. Oceanographic studies of epipelagic ammonium distributions: The Ross Sea NH4 + flux experiment. In W. R. Siegfried (Ed.), Fourth SCAR Symposium Antarctic Biology. New York: Springer-Verlag. Biscaye, P.E., and S.L. Eittreim. 1977. Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean. Marine Geology, 23, 155 - 172. Bishop, J.K.B., J.M. Edmond, P.R. Ketten, M.P. Bacon, and W.B. Silker. 1977. The chemistry, biology, and vertical flux of particulate matter from the upper 400m of the equatorial Atlantic Ocean. Deep-Sea Research, 24, 511 - 548. Dunbar, R.B., J.B. Anderson, and A. Leventer. 1984. Water column fluxes and biogenic sediments of the Ross Sea and Bransfield Strait, Antarctica. Abstracts with Programs, Annual Meeting, Geological Society of America, 16, 496. Dunbar, R.B., J.B. Anderson, E.W. Domack, and S.S. Jacobs. In pres. Oceanographic influences on sedimentation along the Antarctic co ntinental shelf. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Shelf. (Antarctic Research Series.) Washington, D.C.: American Geophysical Union. Elverhoi, A., and E. Roaldset. 1983. Glaciomarine sediments and suispended particulate matter, Weddell Sea Shelf, Antarctica. Polar search, 1 n.s., 1 - 21. Foster, T.D., and E.C. Carmack. 1976. Frontal zone mixing and Antarctic Bottom Water formation in the southern Weddell Sea. Deep-Sea Research, 23, 301 - 317. Gibbs, R.J. 1974. Principles of studying suspended materials in water. In R.J. Gibbs (Ed.), Suspended solids in water. New York: Plenum Press. Jacobs, S.S., A.F. Amos, and P.M. Bruchhausen. 1970. Ross Sea oceanography and Antarctic Bottom Water formation. Deep-Sea Research, 17, 935-962. ANTARCTIC JOURNAL
Krebs, W.N. 1983. Ecology of neritic marine diatoms, Arthur Harbor, Antarctica. Micropaleontology, 29(3), 267 - 297. La!, D., and A. Lerman. 1973. Dissolution and behavior of particulate biogenic matter in the ocean: Some theoretical considerations. Journal of Geophysical Research, 78, 7100 - 7111. Lisitzin, A.P. 1972. Sedimentation in the world ocean. (SEPM Special Publication 17.) Tulsa, Ok.: Society of Economic Paleontologists and Mineralogists.
Smith, W. 0., and D. Nelson. 1985. Phytoplankton bloom produced by receding ice edge in the Ross Sea: Spatial coherence with the density field. Science, 227, 163 - 166. Sullivan, C.W., A.C. Palmisano, S. Kottmeier, and R. Moe. 1982. Development of the sea-ice microbial community in McMurdo Sound. Antarctic Journal of the U.S., 17(5), 155 - 157.
Wilkes Land Expedition 1985
L. Hunt's group at the University of California, Irvine, conducted ornithological research, and David L. Garrison from the University of California, Santa Cruz, conducted biological oceanographic studies. Technical assistance was provided by Timothy J. Fields and James A. Schmitt from Scripps Institution of Oceanography and by the Marine Science Department of the
THEODORE D. FOSTER
Marine Sciences University of California Santa Cruz, California 95064
Polar Star.
50°E
160°E 65°S
650S
The Wilkes Land Expedition 1985 sought to study an almost unexplored region of the southern oceans off Wilkes Land between 147° and 162°E. The scientific party embarked on the U.S. Coast Guard icebreaker Polar Star on 12 February 1985 at McMurdo Station, Antarctica, and disembarked on 9 March 1985 at Wellington, New Zealand. The primary impetus for the expedition was the suggestion of Carmack and Killworth (1978) that this region may be a source of deep water which may be an important contribution to the abyssal waters of the world ocean. Satellite sea-ice observations have shown that this region is nearly always ice-covered even in austral summer; 1985 proved to be no exception. The continental shelf portion of the region was found to be covered with closely packed ice floes. The icebreaking capabilities of the ship limited penetration of the region to the edges of the ice pack. Nevertheless, most of the region was explored. The primary research program's goal was to make a physical and chemical reconnaissance of the potential deep-water formation region. The physical oceanography program was directed by Theodore D. Foster of the University of California, Santa Cruz, and included participation by Miao Yutian, a scientific observer from the Second Institute of Oceanography of the People's Republic of China, and Eric C. Eckert of the University of California, Santa Cruz. The chemical oceanography program was under the direction of Robert L. Michel of Scripps Institution of Oceanography and included participation by Roy A. Schroeder of the United States Geological Survey, Robin S. Keir of Scripps Institution of Oceanography, and Frederick A. Van Woy from Ray F. Weiss' group at Scripps Institution of Oceanography. In addition to the investigation of deep-water formation, Nancy M. Harrison and Zoe A. Eppley from George
195 REVIEW
70°S
50E
1600E
700 S
Track of Polar Star and positions of hydrographic stations during Wilkes Land Expedition 1985.
The figure shows the cruise track of Polar Star in the potential deep-water formation region off Wilkes Land. A total of 86 hydrographic stations were occupied in this region. In addition, two test stations were occupied proceeding to the area, and five hydrographic stations were attempted on the transit to Wellington. Winch failure and inability of Polar Star to carry out satisfactory open-water hydrographic work, as well as a shortened cruise, prevented completion of this section. Reference Carmack, E. C., and P.D. Killworth. 1978. Formation and interleaving of abyssal water masses off Wilkes Land, Antarctica. Deep-Sea Research, 25, 357 - 369.
103
