United States Antarctic Program Research Articles

Doubling the known diversity of a remote island fauna: marine bivalves of the Juan Fernández and Desventuradas oceanic archipelagos (Southeastern Pacific Ocean).

Juan Fernández and Desventuradas are two oceanic archipelagos located in the southeastern Pacific Ocean far off the Chilean coast that received protected status as marine parks in 2016. Remoteness and access difficulty contributed to historically poor biodiversity sampling and limited associated research. This is particularly noticeable for bivalves, with most prior regional publications focused on single taxa or un-illustrated checklists. This study investigates marine bivalves collected between the intertidal and 415 m depth during (1) the 1997 IOC97 expedition aboard the M/V Carlos Porter, with special focus on scuba-collected micro-mollusks of both archipelagos, (2) two expeditions by the R/V Anton Bruun (Cruise 12/1965 and Cruise 17/1966), and (3) Cruise 21 of USNS Eltanin under the United States Antarctic Program, which sampled at Juan Fernández in 1965. Also, relevant historical material of the British H.M.S. Challenger Expedition (1873-1876), the Swedish Pacific Expedition (1916-1917), and by German zoologist Ludwig H. Plate (1893-1895) is critically revised. A total of 48 species are recognized and illustrated, including 19 new species (described herein) and six other potentially new species. The presence of two species mentioned in the literature for the region (Aulacomya atra and Saccella cuneata) could not be confirmed. The genera Verticipronus and Halonympha are reported for the first time from the Eastern Pacific, as are Anadara and Condylocardia from Chilean waters. Lectotypes are designated for Arca (Barbatia) platei and Mytilus algosus. These findings double the number of extant bivalve species known from the Juan Fernández and Desventuradas archipelagos, highlighting the lack of attention these islands groups have received in the past. A high percentage of species endemic to one or both archipelagos are recognized herein, accounting for almost 78% of the total. The newly recognized level of bivalve endemism supports the consideration of Juan Fernández and Desventuradas as two different biogeographic units (Provinces or Ecoregions) of the Eastern Pacific Ocean.

Remote and autonomous measurements of precipitation for the northwestern Ross Ice Shelf, Antarctica

Abstract. The Antarctic Precipitation System project deployed and maintained four sites across the northwestern Ross Ice Shelf in Antarctica from November 2017 to November 2019. The goals for the project included the collection of in situ observations of precipitation in Antarctica spanning a duration of 2 years, an improvement in the understanding of precipitation events across the Ross Ice Shelf, and the ability to validate precipitation data from atmospheric numerical models. At each of the four sites the precipitation was measured with an OTT Pluvio2 precipitation gauge. Additionally, snow accumulation at the site was measured with a sonic ranging sensor and using GPS interferometric reflectivity. Supplemental observations of temperature, wind speed, particle count, particle size and speed, and images and video from a camera were collected to provide context to the precipitation measurements. The collected dataset represents some of the first year-round observations of precipitation in Antarctica at remote locations using an autonomous measurement system. The acquired observations have been quality-controlled and post-processed, and they are available for retrieval through the United States Antarctic Program Data Center (https://doi.org/10.15784/601441, Seefeldt, 2021).

Antarctic atmospheric boundary layer observations with the Small Unmanned Meteorological Observer (SUMO)

Abstract. Between January 2012 and June 2017 a small unmanned aerial system (sUAS), known as the Small Unmanned Meteorological Observer (SUMO), was used to observe the state of the atmospheric boundary layer in the Antarctic. During six Antarctic field campaigns, 116 SUMO flights were completed. These flights took place during all seasons over both permanent ice and ice-free locations on the Antarctic continent and over sea ice in the western Ross Sea. Sampling was completed during spiral ascent and descent flight paths that observed the temperature, humidity, pressure and wind up to 1000 m above ground level and sampled the entire depth of the atmospheric boundary layer, as well as portions of the free atmosphere above the boundary layer. A wide variety of boundary layer states were observed, including very shallow, strongly stable conditions during the Antarctic winter and deep, convective conditions over ice-free locations in the summer. The Antarctic atmospheric boundary layer data collected by the SUMO sUAS, described in this paper, can be retrieved from the United States Antarctic Program Data Center (https://www.usap-dc.org, last access: 8 March 2021). The data for all flights conducted on the continent are available at https://doi.org/10.15784/601054 (Cassano, 2017), and data from the Ross Sea flights are available at https://doi.org/10.15784/601191 (Cassano, 2019).

Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America

The orbiniid polychaetes chiefly from Antarctic and subantarctic seas and off South America are described based on collections of the National Museum of Natural History and new material from surveys conducted by the United States Antarctic Program and other federal and privately funded sources as well as participation in international programs. A total of 44 species of Orbiniidae distributed in 10 genera are reported from the Pacific Ocean and waters off South America and Antarctica. Twenty-one species are new to science; one species is renamed. Berkeleyia heroae n. sp., B. abyssala n. sp., B. weddellia n. sp.; B. hadala n. sp., Leitoscoloplos simplex n. sp., L. plataensis n. sp., L. nasus n. sp., L. eltaninae n. sp., L. phyllobranchus n. sp., L. rankini n. sp., Scoloplos bathytatus n. sp., S. suroestense n. sp., Leodamas hyphalos n. sp., L. maciolekae n. sp., L. perissobranchiatus n. sp., Califia bilamellata n. sp., Orbinia orensanzi n. sp., Naineris antarctica n. sp., N. argentiniensis n. sp., Orbiniella spinosa n. sp., and O. landrumae n. sp. are new to science. A new name, Naineris furcillata, replaces N. chilensis Carrasco, 1977, a junior homonym of N. dendtritica chilensis Hartmann‑Schröder, 1965, which is raised to full species status. Leodamas cochleatus (Ehlers, 1900) is removed from synonymy and redescribed. A neotype is established for Leodamas verax Kinberg, 1966, the type species. A general overview of Leodamas species is provided. The Leitoscoloplos kerguelensis (McIntosh, 1885) complex is reviewed and partially revised. Definitions of the genera of the Orbiniidae are updated to conform to recently described taxa. Several new synonymies are proposed following a reexamination of previously described type specimens. The morphological characters used to identify and classify orbiniids are reviewed. The biogeographic and bathymetric distributions of the South American and Southern Ocean orbiniid fauna are reviewed.

Observations of the atmosphere and surface state over Terra Nova Bay, Antarctica, using unmanned aerial systems

Abstract. In September 2012 five Aerosonde unmanned aircraft were used to make measurements of the atmospheric state over the Terra Nova Bay polynya, Antarctica, to explore the details of air–sea ice–ocean coupling. A total of 14 flights were completed in September 2012. Ten of the flight missions consisted of two unmanned aerial systems (UAS) sampling the atmosphere over Terra Nova Bay on 5 different days, with one UAS focusing on the downwind evolution of the air mass and a second UAS flying transects roughly perpendicular to the low-level winds. The data from these coordinated UAS flights provide a comprehensive three-dimensional data set of the atmospheric state (air temperature, humidity, pressure, and wind) and surface skin temperature over Terra Nova Bay. The remaining UAS flights during the September 2012 field campaign included two local flights near McMurdo Station for flight testing, a single UAS flight to Terra Nova Bay, and a single UAS flight over the Ross Ice Shelf and Ross Sea polynya. A data set containing the atmospheric and surface data as well as operational aircraft data have been submitted to the United States Antarctic Program Data Coordination Center (USAP-DCC, http://www.usap-data.org/) for free access (http://gcmd.nasa.gov/getdif.htm?NSF-ANT10-43657, doi:10.15784/600125).

Scientific Exploration in Antarctica as an Analogy for American Spaceflight

The United States Antarctic Program (USAP) provides a revealing analogy to American spaceflight owing to its common historical origin, similar base in Cold War national security and diplomacy, and reciprocal influence of scientific research and technology development associated with Antarctica and outer space. In addition, the USAP and America’s space program have been high-profile federal endeavors, promoted by varying constituents through unifying narratives intended to elicit “public understanding” or, more pointedly, public support for these strategic national initiatives. Beginning in the late 1950s, initial narratives similarly depicted both programs as confirmation that the United States was a benevolent world power which deployed its preeminent science and technology to positively transform distant realms and make their bounty serve humankind. As domestic priorities and international affairs dramatically shifted at the end of the 1960s, public discourse about the U.S. Antarctic and space programs changed and diverged. The USAP came to embody a national commitment to protecting the global environment while American spaceflight evinces more mixed national aspirations. A comparative account of this initial convergence and ultimate divergence exposes the cultural politics of these federal initiatives and helps reveal the process by which boosters and commentators cultivated public understanding and support for these strategic national endeavors.

Unmanned aircraft system measurements of the atmospheric boundary layer over Terra Nova Bay, Antarctica

Abstract. In September 2009, a series of long-range unmanned aircraft system (UAS) flights collected basic atmospheric data over the Terra Nova Bay polynya in Antarctica. Air temperature, wind, pressure, relative humidity, radiation, skin temperature, GPS, and operational aircraft data were collected and quality controlled for scientific use. The data have been submitted to the United States Antarctic Program Data Coordination Center (USAP-DCC) for free access (doi:10.1594/USAP/0739464).

Spatial patterns of total petroleum hydrocarbons in the terrestrial environment at McMurdo Station, Antarctica

AbstractFossil fuels are used throughout the United States Antarctic Program. Accidental releases of petroleum hydrocarbons are the leading source of environmental contamination. Since 1999 McMurdo Station has been the site of the most extensive environmental monitoring programme in Antarctica. Nearly 2500 surface soil samples were collected from 1999–2007 to determine the spatial “footprint” of petroleum hydrocarbons. Total petroleum hydrocarbons (TPH) concentrations were measured using a high-resolution capillary gas chromatographic method with flame ionization detection. Three distinct TPH patterns were detected: low molecular weight gasoline/JP5/AN8, residual weathered petroleum and an unresolved complex mixture of high molecular weight material. Overall TPH concentrations were low with 38% of the samples having TPH concentrations below 30 ppm and 58% below 100 ppm. Total petroleum hydrocarbon concentrations above 30 ppm are largely confined to the central portions of the station, along roads and in other areas where elevated TPH would be expected. Peripheral areas typically have TPH concentrations below 15 ppm. Areas of elevated TPH concentrations are patchy and of limited spatial extent, seldom extending over distances of 100 m. This environmental monitoring programme is ongoing and can serve as an example to other Antarctic programmes concerned with monitoring environmental impacts.

Physical Activity and the Incidence of Acute Mountain Sickness in United States Antarctic Program Participants Following Rapid Transport to the South Pole: Antarctic Study of Altitude Physiology (ASAP)

BackgroundPhysical activity has been proposed as a risk factor for altitude illness however it is unclear whether the total amount or intensity of activity determines illness.PurposeTo examine activity patterns relative to the incidence of acute mountain sickness (AMS) in United States Antarctic Program workers rapidly transported to the South Pole (SP, 9303 ft).Methods53 medically screened subjects (age=37±10yr, BMI=24±3 kg/m2) were transported by a 3 hour flight from McMurdo Station (sea level, SL) to the SP. Physical activity was monitored at SL and for 3 days after ascent using BodyMedia® activity monitors. Symptoms of AMS were assessed using Lake Louise Questionnaires.Results53% of subjects displayed AMS between SP days 1–3 (23% day 1, 43% day 2, 15% day 3). Energy expenditure at SP was 3414±944, 3458±781, & 3543±869 Calories/day for days 1–3, respectively. Steps/day at SP was 12593±4926, 13124±4392, & 12966±4482 for days 1–3, respectively. Overall, more activity at higher intensity (>3 METS) on SP day 1 was associated with higher AMS incidence the next morning (p<0.05). Also, calorie expenditure with activity at >3 METS and time of activity at >6 METS in the first 24 hours after ascent independently increased the odds of AMS on SP day 2 (p<0.05).ConclusionsWith rapid transport to altitude, moderate to intense activity within the first 24 hours of ascent contributes to the incidence of AMS. NSF ANT 0540710

Variability in pulmonary function changes in United States Antarctic Program participants following rapid transport to the South Pole

Maximal expiratory flows (MEF) are dependent on gas density, lung volume, subject effort and airway characteristics. Variable changes in MEF occur after ascent to altitude which may represent an interaction between gas density changes, catecholamine stimulation and mild interstitial edema. Hypoxia induced catecholamine up‐regulation has also been associated with acute mountain sickness (AMS). This study examined the association between MEF variability and AMS symptoms in United States Antarctic Program personnel (n=198, age 37±1 yrs, 3% asthma) rapidly transported to the South Pole (SP, 9302 ft). Spirometric parameters, epinephrine (Epi), norepinepherine (NE) and SaO2 levels were recorded at sea level (SL, McMurdo Station) and after the 2nd night at SP. AMS was assessed using Lake Louise questionnaires (score ≥ 3). FVC, FEV1, FEF25, FEF75 and FEF25–75 increased by 0, 3, 17, 10 and 14% from SL to SP, respectively. On day 2, AMS incidence was 31% and Epi and NE increased by 44 and 71%. Changes in MEF ranged from −64 to +93% in FEF25–75 and −63 to +70% in FEF75. Subjects with the greatest increase in MEF had higher incidence of AMS (24 vs 41%) and higher NE levels, while the subjects with the greatest decrease in MEF had lower SaO2 values (88 vs 90%). Subjects with increased MEF had increased AMS and bronchodilation while subjects with decreased MEF displayed values consistent with mild interstitial edema.

The historical development of McMurdo station, Antarctica, an environmental perspective

McMurdo Station is the logistics hub of the United States Antarctic Program, and localized environmental impacts have accompanied its nearly 50 years of continuous operation. An extensive collection of aerial photographs were used to map changes in the buildings, fuel storage tanks, roads, and physically disturbed areas at McMurdo Station since its establishment in 1956. From 1956 and continuing through the 1960s, rapid expansion of the station occurred. From 1970 until present, the area impacted by human activities has increased but at a much decreased rate. Current station operations are largely confined to areas that had already been impacted in the first 10–15 years of the station operations. The spatio-temporal perspective on McMurdo Station's growth provides a baseline from which future changes in the spatial extent of areas impacted by human activities can be monitored as required by the Protocol on Environmental Protection to the Antarctic Treaty.

Observations of fuel transport on sea ice from two fuel release events, with relevance to site assessment and closure

The use and distribution of fossil fuels, particularly Antarctic-8 (AN-8), a kerosene-based fuel blended with anti-gelling additives, significantly supports United States Antarctic Program (USAP) operations. Despite best fuel management practices, two large-scale (greater than 7000 L) fuel releases have occurred as point source releases from the flexible fuel line connecting McMurdo Station, Antarctica to the early summer airfield. The first release resulted in the loss of approximately 26,500 L of AN-8 onto the sea ice surface through a 1.37-meter (m) snow cover. The second fuel release occurred in a subsequent year and resulted in the loss of approximately 8300 L of AN-8 onto the sea ice surface through a 0.15 m snow cover. In both fuel release events, the fuel migrated through the snow cover to the sea ice, dispersed across the surface of the sea ice along the snow-sea ice interface. Two conditions primarily affected fuel migration, extent of sea ice contamination, and incident fuel recovery in the large-scale fuel releases: 1) sea ice age and associated properties and 2) the amount of snow coverage and handling of contaminated snow at the site(s). Sea ice core samples analyzed for total petroleum hydrocarbons (TPH) concentration were used to determine the extent of fuel infiltration and contamination to the sea ice.

Innovations in over-snow cargo transport

The United States Antarctic Program (USAP) is developing tractor-sled trains to haul heavy cargo 1600 km from McMurdo Station to South Pole Station. In 2003, the proof-of-concept fleet experienced poor mobility and numerous sled breakdowns when attempting to cross the Ross Ice Shelf. Based on in-situ mobility tests, we recommended several expedient changes to the sled trains: tow the sleds outside of the tractor ruts, build larger skis with elliptical noses, and accommodate sled motions via compliant bushings. The USAP adopted these recommendations, the sleds performed well, and the fleet completed its first successful cargo delivery to South Pole in December 2005. For that season, we designed and the fleet successfully trialed a novel fuel sled consisting of a transportable fuel bladder strapped onto a sheet of durable, low-friction plastic. The resulting sled costs about one-quarter that of a steel tank sled, has about one-eighth of the tare weight and increases the expected fuel delivered per tractor almost nine times. The durability of these bladder sleds over rough terrain must yet be assessed, but their high fuel-delivery efficiency, compared with the present method of aircraft delivery, is worth pursuing. For example, a seven-tractor fleet completing three round trips per season could deliver fuel to South Pole equivalent to 92 LC-130 flights while consuming about one-quarter of the fuel required for aircraft delivery. Economic analysis shows that reduced aircraft costs could payoff the capital cost of a traverse fleet within a single season.

Tractolira delli, a new Volutidae (Mollusca: Gastropoda: Neogastropoda) from the abyssal plains off Antarctica

A new deep-sea species of Volutidae in the genus Tractolira is named from material collected by the United States Antarctic Program in and around the Ross Sea, eastern Antarctica, and from one locality in the Subantarctic region. Tractolira delli new species is most similar to T. sparta Dall, 1896, from which it differs in having a relatively wider shell, less prominent spiral sculpture, with narrower threads, and by the absence of strong axial ribs at least on the first three teleoconch whorls. The other Antarctic congener, Tractolira germonae, has a thicker, dark-brown periostracum (instead of a thin, light-yellow one), a proportionally smaller inductura, and lacks surface sculpture.

The Song of Hypothermia

Click for larger view Figure 1 [End Page 44] There's no such thing as being out of the wind in the Antarctic. We inhabit a barren continent buried under mile-deep ice and shaped by the cold gales of millennia. Katabatic winds plunge down to the frozen coast like an endless train falling off its tracks. Here on the Odell Glacier, sleep comes under a steady barrage of twenty-five-knot gusts that struggle to erase our little nylon home on the ice. It's early November, and Julian and I have set up camp in the Transantarctic Mountains, two men isolated for three months of the Antarctic summer. The south polar sun will not set during our three months, instead spinning above us like an anemometer. And already it seems that the wind will be a very busy neighbor: our little tents creak, our little tents hum. We have two goals out here: first, to build and maintain an emergency runway on the glacier. McMurdo Station, the main base for the USAP (United States Antarctic Program), needs an alternative landing site for the large Hercules aircraft that bring cargo from New Zealand or move it around the continent. Several times each summer, storm or fog make Herc landings in McMurdo too dangerous. [End Page 45] Our other goal: to keep each other sane, with only ourselves for company for the next ninety days. Our camp is on the edge of the five-mile-wide Odell Glacier, snug under the shadow of a steep dolomite ridge of the Allan Hills. The sloping edge of the glacier and a curve in the hills make a small cove that offers us some protection. The gusts baffle around our neighborhood of blue ice and brown stone; winds shudder and fall into the cove rather than racing through. Because of the shuddering, snow drops out of the flow and drifts up against the rocks. This we shovel out and melt for water. We don't know how difficult the katabatic winds will be this summer, but we have to plan on the worst—day after day of tent-thrashing. Though Julian and I plan to look around further, in a few preliminary trips out here last summer I found no better hiding place on the glacier. Which is too bad because after only a few hours on the Odell, everything we own is tied down and shaking. Katabatic winds are avalanches of air. They are the characteristic winds of Antarctica, far more common here than elsewhere. The word derives from the Greek katabatos, "descending." The high reflectivity of the white ice sheet reflects most of the sun's heat, leaving intensely cooled air on the surface, which then slides down along the curve of the ice domes. These gravity-driven air masses fall hundreds of miles down from the bitterly cold East Antarctic plateau over smooth surfaces of snow and ice. They howl most fiercely when squeezed down narrow glaciers (like the Odell) between nunataks, the visible peaks of mountains otherwise submerged by ice. The Allan Hills, like other nunataks, shape and are shaped by the winds. Katabatics begin and end abruptly. They are ragged and gusty, arrive under clear skies and may easily last days or weeks. They blow nearly continually in the most afflicted areas: Douglas Mawson's 1912 winter quarters in Commonwealth Bay shook constantly in katabatics averaging fifty miles per hour through their first year, with gusts of over two hundred miles per hour. In Home of the Blizzard, Mawson wrote of this time that they "dwelt on the fringe of an unspanned continent, where the chill breath of a vast, polar wilderness, quickening to the rushing might of eternal blizzard, surged to the northern seas. We had discovered an accursed country." As I lie in my only slightly accursed tent on our first Odell evening, on the fringe of our now-spanned continent, I mull over my last harried words to friends in McMurdo: "You can go to MacOps...

Real-Time Mesoscale Modeling Over Antarctica: The Antarctic Mesoscale Prediction System*

In support of the United States Antarctic Program (USAP), the National Center for Atmospheric Research and the Byrd Polar Research Center of The Ohio State University have created the Antarctic Mesoscale Prediction System (AMPS): an experimental, real-time mesoscale modeling system covering Antarctica. AMPS has been designed to serve flight forecasters at McMurdo Station, to support science and operations around the continent, and to be a vehicle for the development of physical parameterizations suitable for polar regions. Since 2000, AMPS has been producing high-resolution forecasts (grids to 3.3 km) with the “Polar MM5,” a version of the fifth-generation Pennsylvania State University-NCAR Mesoscale Model tuned for the polar atmosphere. Beyond its basic mission of serving the USAP flight forecasters at McMurdo, AMPS has assisted both in emergency operations to save lives and in programs to explore the extreme polar environment. The former have included a medical evacuation from the South Pole and a marine rescue from the continental margin. The latter have included scientific field campaigns and the daily activities of international Antarctic forecasters and researchers. The AMPS program has been a success in terms of advancing polar mesoscale NWP, serving critical logistical operations of the USAP, and, most visibly, assisting in emergency rescue missions to save lives. The history and performance of AMPS are described and the successes of this unique real-time mesoscale modeling system in crisis support are detailed.

The caprellidean Amphipoda from the subantarctic islands of New Zealand and Australia with the description of a new genus and two new species

The Caprellidea of The Snares, Antipodes Islands, Auckland Islands, Campbell Island and Macquarie Island are reported from collections made between 1973 and 1977 by the Australian Museum, and collections made between 1967 and 1972 by researchers associated with the United States Antarctic Program (USAP). One new genus, Caprellaporema, and two new species, Caprellaporema subantarctica and Pseudaeginella campbellensis are described, Caprella manneringi McCain, 1979 is redescribed, and lateral view figures of the remaining species of the subantarctic islands are also provided.

Antarctic Mesoscale Prediction System (AMPS): A Case Study from the 2000–01 Field Season*

To support the forecasting needs of the United States Antarctic Program at McMurdo, Antarctica, a special numerical weather prediction program, the Antarctic Mesoscale Prediction System (AMPS), was established for the 2000–01 field season. AMPS employs the Polar MM5, a version of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) that has physics modifications for polar environments. This study assesses the performance of AMPS in forecasting an event of mesoscale cyclogenesis in the western Ross Sea during 13–17 January 2001. Observations indicate the presence of a complex trough having two primary mesoscale lows that merge to the east of Ross Island shortly after 0700 UTC 15 January. In contrast, AMPS predicts one primary mesoscale low throughout the event, incorrectly placing it until the 1800 UTC 15 January forecast, when the observed system carries a prominent signature in the initialization. The model reproduces the evolution of upper-level conditions in agreement with the observations and shows skill in resolving many small-scale surface features common to the region (i.e., katabatic winds; lows and highs induced by wind/topography). The AMPS forecasts can rely heavily on the representation of surface lows and upper-level forcing in the first-guess fields derived from NCEP's Aviation Model (AVN). Furthermore, even with relatively high spatial resolution, mesoscale models face observation-related limitations on performance that can be particularly acute in Antarctica.

High-resolution paleomagnetic records from Holocene sediments from the Palmer Deep, Western Antartic Peninsula

Thick Holocene sedimentary sections (>45 m) cored in the Palmer Deep by the United States Antarctic Program (USAP) and during Ocean Drilling Program (ODP) Leg 178 provide the first opportunity to examine past geomagnetic field behavior at high southern latitudes. After removal of a low-coercivity drilling overprint the sediments display a stable, single-component remanent magnetization. Two short cores that recovered the uppermost 2.6 m of sediment have inclinations that fluctuate about the present day inclination (−57°) measured at Faraday Station, and several features with wavelengths of 10 to 20 cm appear to be correlative. However, shipboard measurements of inclination fluctuations on split-core samples from three holes drilled at ODP Site 1098 do not correlate well with each other, even though the intensity and susceptibility data correlate very well and the overall mean inclination for cores from each hole is consistent with the expected geocentric axial dipole (GAD) inclination. The correlation is improved dramatically by using inclinations measured on u-channels taken from the pristine center of a split core. Consequently, the anomalous directions and the resulting poor between-hole correlation of inclinations obtained from shipboard data can be attributed to coring-induced deformation, which is common on the outer edge of ODP piston cores, and/or measurement artifacts in the split-core data. Our preferred inclination record is thus derived from u-channel results. The upper ∼25 m represents continuous sedimentation over the past 9000 yr, with an average sedimentation rate exceeding 250 cm/kyr (0.25 cm/yr). Given that remanence measurements on u-channels average over an interval <7 cm long, we obtained independent measurements of the paleo-geomagnetic field that average over only ∼30 yr. This high-resolution record is characterized by an inclination that fluctuates within ±15° of the current GAD inclination.

Navy closes Antarctic unit

After 42 years as a key participant in the United States Antarctic Program (USAP), the U.S. Navy held a ceremony on February 20 to commemorate the closing of its Naval Antarctic Support Unit stationed in New Zealand. The Navy originally had announced its decision to “disestablish” the unit in 1993, citing new global priorities with the end of the Cold War.The Navy will continue to provide limited flight support to the USAP through the end of the 1998–1999 austral research season.