Hallett Station Research Articles

Antarctic Ecosystem Recovery Following Human-Induced Habitat Change: Recolonization of Adélie Penguins (Pygoscelis adeliae) at Cape Hallett, Ross Sea

The human-induced disturbances in Antarctica have caused changes in the structure and function of ecosystems. The Cape Hallett station was established in 1957 and abandoned in 1973. The station was built inside a penguin colony, and during its operation, many penguins were deported. Herein, we compared the number of breeding pairs across different time periods after station decommission and environmental remediation. The station occupied 4.77 ha within the Adélie penguin breeding area, and 349 nests were identified inside the station border in 1960. In 1983, the station’s territory decreased to 4.2 ha; meanwhile, 1683 breeding pairs were counted in the old station area. The past station area re-inhabited by Adélie penguins had 6175 nests in 2019. We assumed that recolonization might be particularly related to artificial mounds. The results of the present study confirm the recolonization of Adélie penguins at Cape Hallett for the first time, with visual analysis of spatial-temporal changes. Additionally, we suggest that reconstruction of the artificial or enhanced habitat may be required for successful restoration. Furthermore, continuous species monitoring with specific notes are needed with management interventions to protect Antarctic ecosystems, as well as the Ross Sea region MPA.

The diurnal variation in magnetic activity at Scott Base and Hallett Station

Abstract Magnetic activity at Scott Base and Hallett Station is examined by K-indices. The diurnal variation of magnetic disturbance is studied for practically a complete sunspot cycle at Scott Base, and from 1957 to 1962 at Hallett Station. Times of maxima and minima of diurnal variation of magnetic activity for winter, equinox, summer, and year are shown graphically. Magnetic activity is at a minimum in winter, and increases through equinox to a maximum in summer. In general, the diurnal variation of magnetic activity showed a single maximum and minimum except for winter around sunspot minimum. In summer at Scott Base the maximum of the diurnal distribution of magnetic disturbance occurs before geomagnetic noon throughout the sunspot cycle.

The magnetic secular variation at Scott Base and Hallett Station

The secular variations in the magnetic elements at Scott Base and Hallett Station have been determined. For Scott Base they have been derived from mean annual values of the magnetic elements in 1958 and 1965. The secular variations for Hallett Station have been obtained from very limited data of mean monthly values of the magnetic elements from April 1961 to December 1962. As the Scott Base results are derived over a longer period they would be more accurate than those for Hallett Station. The results at both these stations are comparable in magnitude and sign except for D which is increasing at Hallett Station and decreasing at Scott Base.

Aspergillus fumigatus Fresenius isolated from ornithogenic soil collected at Hallett Station, Antarctica.

Aspergillus fumigatus was isolated with high frequency from samples of ornithogenic soil collected from an Adélie penguin rookery at Hallett Station, Antarctica. While A. fumigatus has been well documented as the principal incitant of aspergillosis among penguins in captivity, this represents the first report of its presence in antarctic materials. Aspergillus flavus and Aspergillus ustus were also found in the Hallett samples. In a comparable number of soil and guano samples from isolated Adélie rookeries on Foyn Island and Possession Island, these fungi were not encountered. It is suggested that their presence at Hallett Station may be the result of human contamination. A brief consideration of epidemiological implications is given.

Soils of Taylor Dry Valley, Victoria Land, Antarctica, with notes on soils from other localities in Victoria Land

Abstract A map and descriptions of the soils of Taylor Dry Valley, Victoria Land, Antarctica, are presented. Soils from Hallett Station, Ross Island, and other places around McMurdo Sound are briefly described and compared with those of Taylor Dry Valley. The role of the soil-forming factors and the nature of the soil.forming processes in Victoria Land is discussed. Soils on “normal sites” (e.g., on slightly elevated gentle slopes on moraine or similar parent material) may be regarded as zonal soils. They are virtually lithochromic, coarse textured, structureless, and without humic horizons. Two groups are recognised: (a) Those in arid Taylor Dry Valley, which have a surface or subsurface layer slightly to moderately cemented with calcium carbonate or gypsum and are underlain at depths of about 12 in. by frozen ground. (b) Those outside Taylor Dry Valley, e.g., at Hallett Station and Ross Island and also at high elevations; more moisture is available, probably from more frequent summer snowfalls, and soluble materials are distributed throughout the soils and do not form surface crusts. Soils with much moisture and those rich in organic matter are classed as intrazonal.

Thickness Of The Earth's Crust Beneath The Pacific-Antarctic Ridge

Abstract The dispersion of earthquake waves propagated along the Pacific-Antarctic Ridge indicates that the crust is 6-7 km thick beneath the Ridge and slightly thinner beneath the adjacent deep water.Strong Love waves are recorded at Hallett Station from earthquakes on the Pacific-Antarctic Ridge, whereas strong Rayleigh waves are recorded from those on the East Pacific Rise; this difference is attributed to the source rather than to the medium.The structure of the Pacific-Antarctic Ridge appears to be intermediate between those found by other workers for the East Pacific Rise and the Mid-Atlantic Ridge.

Vegetation on Hallett Station Area, Victoria Land, Antarctica

Vegetation on Hallett Station Area, Victoria Land, Antarctica

A note on the observations of twilight lithium emission made from Hallett Station

Occasional observations of strong increases in the atmospheric sodium densities and/or Na nightglow intensities suggest that the cause is the deposition of a sodium cloud in addition to the local equilibrium sodium layer. This situation is simulated to investigate the response of the atmospheric sodium layer to variations of the source influx rate. The settlement of the sodium to the equilibrium layer after the deposition of a sodium cloud is shown to be a long lived event in which the excess sodium is transported downwards, to the sink, by eddy diffusion. The possibility of a modulated source influx rate is also investigated showing a tendency for a strong attenuation of this modulation below the source.

Orientation of Polar Auroras

Weill (1958) has shown that the orientation of "homogeneous arc" auroras at Dumont d'Urville (see Fig. 1) exhibits definite diurnal variation, the arcs being aligned approximately on the azimuth of the Sun. Hatherton and Midwinter (1960), in considering morphology of the auroras near Scott Base and Hallett Station express the opinion that the Dumont d'Urville auroral behaviour .seems unique.

Electrical resistivity of frozen earth

Cook [1960] has described laboratory experiments on the RF electrical properties of synthetic salty ice and frozen earth and has commented on the scarcity of available data concerning the electrical properties of natural sea ice and permafrost with which to compare his results. During IGY the d-c resistivities of the ground upon which Scott Base (latitude 77°51′S) and HaJlett Station (latitude 72°9′S) are constructed were measured, and this note presents the d-c resistivities of the natural frozen ground and compares them with the RF resistivities of the synthetic soils used by Cook. Pram Point, Ross Island, on which Scott Base is built, consists of basaltic debris, with a good deal of clay material, overlying the basalt flows of the Hut Point Peninsula. Except for the top 5 to 10 cm, which thaws for a very short period during the summer months, the ground is permanently frozen. Hallett Station lies on the gravel spit attached to Cape Hallett, and in at least the upper 2 meters of this soil there is some penguin guano. Resistivities measured at these bases during January 1958 by the standard d-c method (commutated) using the Wenner electrode configuration are shown in Figure 1. At Scott Base two expanding electrode profiles were measured in different areas on Pram Point. At Hallett Station only one locality was occupied.

Thickness of the Earth's Crust in Antarctica and the Surrounding Oceans

Love waves and Rayleigh waves from eight earthquakes recorded at Hallett Station, Scott Base and Mirny have been analysed and the dispersion compared with that predicted by theory for simple model crusts. The average thickness of the crust in eastern Antarctica is found to be about 35 km, as is typical of continents, whereas Marie Byrd Land with an average thickness of about 25 km cannot be regarded as truly continental. Love wave dispersion indicates that the thickness of the solid crust in the oceanic regions surrounding Antarctica varies from about 5 km to 10 km, the smaller values being associated with the deeper basins. It is shown that the determination of oceanic crustal thickness from Rayleigh wave dispersion is in general subject to large uncertainties, nor can one usually rely on values of the thickness of unconsolidated bottom sediments obtained by this means.

Observations of the Aurora Australis at New Zealand Antarctic stations during IGY

Intensive auroral observations at Scott Base and Hallett Station during IGY indicate that auroral activity is higher than has previously been estimated at these latitudes. The distribution of auroral activity is not simple; it appears to consist of two superimposed systems, one of isolated rays and the other of arcs and bands, symmetrical about different axes. Orientation of the principal arcs fits a zone which takes account of the nondipole field better than one based on the centered geomagnetic dipole, though the auroral frequencies conflict with this. Auroral activity increases with local geomagnetic disturbance at Hallett Station, but at Scott Base there is negligible increase in the probability of auroral occurrence until K = 5. However, the diurnal variation of auroral frequency, which is bimodal with the primary maximum at 04 hours local time and the secondary maximum at 17 hours local time, does not appear to be related to the diurnal trend of local geomagnetic disturbance, but the principal auroral events inside the zone seem to coincide with the principal magnetic events in the Stagg transition zone. The only characteristic colored form observed, a pale red glow on the horizon, is associated with high magnetic activity and ionospheric absorption. The latitude of auroral forms decreases with increase in K index. The results are compared with those of previous expeditions to Ross Island and Cape Adare.

Diurnal Variation of Aurora and Geomagnetic Disturbance at New Zealand Antarctic Stations

THE diurnal variation of auroral incidence for Scott Base (New Zealand) and Hallett Station (United States–New Zealand) during the International Geophysical Year is shown in Fig. 1A. Curves derived from analyses of concurrent visual and all-sky camera observations are shown separately. The visual curves are based on observations during all hours which have or less cloud cover and the all-sky camera curves on photographs in which the Southern Cross is visible (exposures: Scott Base 20 sec, Hallett Station 15 sec, on Tri-X film). The auroral frequencies were computed from quarter-hourly data except Hallett Station visual for which virtually continuous observations were used. This higher density and also the greater sensitivity of the visual observations at Hallett Station for displays near the horizon and in the presence of moonlight, twilight, and thin cloud lift the Hallett visual frequencies well above the photographic frequencies. The Scott Base visual curve is indistinguishable from the one obtained at Cape Evans during 1911, a period of sunspot minimum, by the British (Terra Nova) Antarctic Expedition1.

Origin of Sodium and Lithium in the Upper Atmosphere

LITHIUM resonance radiation in the twilight air-glow of the southern hemisphere has recently been observed in several places1,2. Over Adelie Land in the Antarctic this radiation is reported to have been present both in 1957 and 1958. In October 1957 its intensity was estimated visually to be of the order of a tenth that of the sodium D lines in the twilight. After the high-altitude nuclear bomb explosion in the Pacific in August 1958 this radiation was also observed at Hallett Station in the Antarctic and afterwards in September at Invercargill in New Zealand. Its intensity is roughly estimated as equal to the total sodium D line intensity at Hallett in August and a tenth of this in New Zealand in September.

Origin of Upper-Atmosphere Lithium Atoms responsible for the New Twilight Airglow at 6708 A.

A NEW emission line near 6708 A. has been reported recently by Delannoy and Weill1 to be present on twilight spectrograms obtained in Adelie Land, Antarctica, during October 1957. Gadsden and Salmon2 also report the appearance of the same line in twilight spectra photographed at Hallett Station, Antarctica, during August, 1958, and at Invercargill, New Zealand, on September 5, 1958. In both instances, the authors attribute the new line to resonance radiation from the 22S—22P transition in the neutral lithium atom at 6707.8 A.

Presence of 6707 A. Radiation in the Twilight Sky

SINCE August 5, 1958, a patrol spectrograph at Hallett Station in Antarctica has frequently shown the presence of a strong emission line in the region of 6705 A. from the twilight sky. Following a report of this, a grating spectrograph at Invercargill, New Zealand, was exposed on September 5, 1958, to the radiation coming from the twilight sky between the horizon and 20° altitude, on a bearing of 175° (true). A feeble line at 6707 ± 2 A. was detected on this occasion, and on several subsequent occasions. The use of a minus ultra-violet filter confirmed that the line was in the first-order spectrum. Exposures at varying states of twilight showed that the line was enhanced in twilight at about the same time as the well-known sodium D-line enhancement. Hallett station has also observed this twilight enhancement, both morning and evening, from the date of the first detection.