Land-based Observations Research Articles

Regulation compliance by vessels and disturbance of harbour seals (Phoca vitulina)

The US National Oceanic and Atmospheric Administration established a buffer zone around marine mammals to prevent harassment. The buffer zone varies by species listing status and by geographic area. However, it is unknown the extent to which vessels comply with these buffer zones. We selected harbor seals ( Phoca vitulina L., 1758) as a case study to describe compliance with the buffer zone. We conducted land-based observations from Yellow Island, Washington State, in a geographic area where the buffer zone is 91 m (100 yards), to estimate vessel distance from hauled-out seals and to evaluate seal response. We recorded 85.7% of kayaks, 57.1% of stopped powerboats, and 4.6% of passing powerboats violating the buffer zone. Seals were disturbed by kayaks and stopped powerboats at distances >91 m from the haul-out sites but not by moving powerboats ≤91 m from the sites. Hence, compliance of the buffer zone varied with vessel type and vessel activity. We suggest that a larger buffer zone for vessels lingering around the haul-out sites and enforcement of the buffer zone will minimize seal disturbance.

Seismological monitoring on the 2003 Tokachi-oki earthquake, derived from off Kushiro permanent cabled OBSs and land-based observations

Japan Marine Science and Technology Center installed a cabled geophysical observatory system off Kushiro, Hokkaido Island in July 1999. This observatory system comprises three ocean bottom seismographs (OBSs), two tsunami gauges, and a geophysical/geochemical monitoring system. 4 years and 2 months after the installation, a megathrust earthquake (the 2003 Tokachi-Oki earthquake, 26th September in Japan Standard Time (JST), M JMA 8.0) occurred along a plate boundary underneath a forearc basin where the system is located. The system recorded clear unsaturated seismograms just at 28.6 km from the epicenter. This paper demonstrates advantages brought by the cabled observatory to record the megathrust earthquake showing how earthquake detectability is improved dramatically combining permanent OBS and land-based observations around the region, and importance of the in situ monitoring on the seismogenic zone. In the present study, processing OBSs and land-based network together, and comparing magnitudes of common observed earthquakes with national authorized network, event detection level improved down to M 1.5, which is much lower than the previously designed as down to M ∼ 2. Comparing detection level before and after installing OBSs, we found dramatic improvement of the earthquake detection level in the interesting region. Real-time continuous observations of microearthquakes since 1999 have brought us tremendous findings. First, a seismic quiescence started about 10 days before the 2003 Tokachi-Oki earthquake. Second, aftershock distribution is not uniform over the focal area and can be divided into several sub-regions, which might indicate an existence of several asperities. We think that the geophysical observations helped to understand the initiation process of the rupture of the 2003 Tokachi-Oki earthquake and that observations including seismological, geodynamic, hydrogeological, and the other multidisciplinary observations would provide a clue to future understanding of seismogenic processes at subduction zones.

A Four-Season Impact Study of Rawinsonde, GOES, and POES Data in the Eta Data Assimilation System. Part II: Contribution of the Components

Abstract The impact of in situ rawinsonde observations (raob), remotely sensed Geostationary Operational Environmental Satellite (GOES), and Polar-Orbiting Operational Environmental Satellite (POES) observations routinely used in NCEP’s Eta Data Assimilation/Forecast System (EDAS) is studied for extended-length time periods during four seasons. This work examines the contribution of nine individual components of the total observing system. The nine data types examined include rawinsonde mass and wind observations, GOES mass and wind observations, POES observations from the Microwave Sounding Unit (MSU), the Advanced Microwave Sounding Unit (AMSU-A and AMSU-B), the High Resolution Infrared Radiation Sounder (HIRS), and column total precipitable water and low-level wind observations from the Special Sensor Microwave Imager (SSM/I). The results are relevant for users of the Eta Model trying to compare/contrast the overall forecast impact of traditional, largely land-based rawinsonde observations against remotely sensed satellite observations, which are available domainwide. The case studies chosen consist of 15-day periods during fall 2001, winter 2001/02, spring 2002, and summer 2002. Throughout these periods, a November 2001 32-km version of the EDAS is run 10 times at both 0000 and 1200 UTC. The 10 runs include a control run, which utilizes all data types routinely used in the EDAS, and 9 experimental runs in which one of the component data types noted above is denied. Differences between the experimental and control runs are then accumulated over the 15-day periods and analyzed to demonstrate the 00-h sensitivity and 24-h forecast impact of these individual data types in the EDAS. The diagnostics are computed over the entire horizontal model domain and a subsection covering the continental United States (CONUS) and adjacent coastal waters on isobaric surfaces extending into the lower stratosphere. The 24-h forecast impact results show that a positive forecast impact is achieved from most of the nine component data sources during all four time periods. HIRS, MSU, and SSM/I wind observations yield only a slight positive forecast impact to all fields. Rawinsonde and GOES wind observations have the largest positive forecast impact for temperature over both the entire model domain and the extended CONUS. The same data types also provide the largest forecast impact to the u component of the wind, while GOES wind observations provide the largest forecast impact to moisture.

北海道十勝沖で2001-2002年に発生した地震活動の陸海地震観測網による震源決定

北海道十勝沖で2001-2002年に発生した地震活動の陸海地震観測網による震源決定

Status of the Mediterranean Monk Seal, Monachus monachus, in the Foça Pilot Monk Seal Conservation Area, Turkey

The status of the Mediterranean Monk Seal, Monachus monachus, has been studied over a five-year period between 1994 and 1998 in the Foça Pilot Monk Seal Conservation Area. The identification of individual seals occurring in the area, their spatial distribution and biology were studied using the results of direct cave surveys, land-based seal observations, and interviews. The population of Monk Seals was estimated to consist of 9 individuals, 6 of which were adult females and 3 were juveniles (one female, one male and one of unknown sex.). Islands off Foça town provide suitable habitats and promote the survival of the species. Of the 11 caves identified, two were found to be used for reproduction.

Foraging Behavior and Resource Partitioning by Diving Birds During Winter in Areas of Strong Tidal Currents

Abstract We investigated the distribution and behavior of 21 species of diving birds wintering in tidally active nearshore ocean off southern Vancouver Island, British Columbia, Canada. Using vessel surveys in one site and land-based observations at a second site, we found significant differences in the use of tidally affected water types among and within three foraging guilds (piscivores, plankton feeders and benthic invertebrate predators) and five families (Gaviidae, Podicipedidae, Phalacrocoracidae, Anatidae, Alcidae). The only abundant plankton feeder, Ancient Murrelets (Synthliboramphus antiquus), foraged more frequently than other birds in areas of deeper water (>10 m) with fast tidal flow and turbulence. Their abundance and diving activity were significantly higher at maximum tide flow than at slack tides. Piscivores used both slack water and moderate currents in a wide range of depths but, apart from alcids and Pelagic Cormorants (Phalacrocorax pelagicus), avoided areas of high current and turbul...

Size and trends of the bowhead whale, beluga and narwhal stocks wintering off West Greenland

To assess the size and trends of the abundance of the bowhead whale (Balaena mysticetus), the beluga, or white whale (Delphinapterus leucas), and the narwhal (Monodon monoceros) visual aerial surveys were conducted in West Greenland in March 1998 and 1999. An estimated 49 bowhead whales (95% CI: 13 to 188) were present at the surface in 1998. Data from land-based observations enabled correction for bowhead whales that were not available at the surface to be seen during the survey. By applying a rounded average of 80% (SE=3) for submergence an estimate of 246 bowhead whales (95% CI: 62 to 978) in 1998 was obtained. The 76 and 47 sightings of beluga pods in 1998 and 1999, respectively, had distributions similar to those of previous surveys with the highest concentration at the northern edge of the northern part of Store Hellefiskebanke. No belugas were seen in the southernmost area between Maniitsoq and Paamiut. The index estimate of the abundance of belugas comparable with previous surveys was 929 (95% CI: 563 to 1,533) in 1998 and 735 (95% CI: 436 to 1,239) in 1999. When analysing the sightings as a line-transect survey and correcting for whales that were either submerged or at the surface but missed by the observers an estimated 7,941 (95% CI: 3,650 to 17,278) belugas wintered in West Greenland in 1998-1999. The uncorrected estimate of narwhal abundance was 524 (95% CI: 214 to 1,284) and correcting for the same biases as for the belugas gives a total abundance of 2,861 (95% CI: 954 to 8,578) narwhals in 1998-1999.

Influence of the tidal cycle and a tidal intrusion front on the spatio-temporal distribution of coastal bottlenose dolphins

Small scale hydrographic fronts may act as convergence zones in which organisms accumulate, and have been used preferentially by several marine predators. In this paper, bottlenose dolphin Tursiops truncatus spatial and temporal distribution was investigated in relation to the tidal cycle and to the spatial and temporal evolution of a tidal front in a narrow estuarine channel. Esti- mates of dolphin abundance during all states of the tidal cycle, and positions of the frontal surface features and of dolphin groups were obtained from land-based observations. Hydrographic data was obtained on the structure of the front. The results showed that the front was characteristic of tidal intrusion fronts and was predictable both temporally and spatially. Its development could be divided into 3 stages. In the first stage the front was determined by the tidal flows and by an unusual fresh- water input at the mouth of the estuary. In later stages the bathymetry and morphology of the estu- ary dominated and the front became stationary until the tidal inflow stopped, causing the front to dissipate. Dolphins were most abundant during the flood tide, particularly during the stationary stage of the tidal front. Dolphins also showed a spatial association with the area near the surface features of the front, which could be related to increased foraging efficiency resulting from the accumulation of prey in the frontal region. Further work that takes account of the 3D distribution and behaviour of the dolphins and their prey with relation to the front is now required to fully understand the nature of this relationship.

Regional Cloud Cover Change Associated with Global Climate Change: Case Studies for Three Regions of the United States

Abstract Land-based observations of cloud cover, for the period 1900–87 and averaged over three geographical regions of the United States (coastal southwest, coastal northeast, and southern plains), show strong positive correlations with one estimate of global mean surface temperature, a finding consistent with prior investigations that suggest cloud cover over land has increased during global warm periods relative to cold periods. It is also found that the strengths of three permanent high/low pressure systems (North Pacific high, Icelandic low, and Azores high) are negatively correlated with global mean surface temperature, suggesting a possible connection between regional cloud cover, for certain locations, and the strengths of adjacent high/low pressure systems. Specifically, for the regions considered it is suggested that the coastal southwest cloud cover is related to changes in the strength of the subtropical North Pacific high, that for the southern plains also to the strength of the North Pacific...

Role of diurnal processes in the seasonal evolution of sea ice and its snow cover

Comparisons between hourly forced data simulations and daily average forced simulations using a one‐dimensional thermodynamic sea ice model show that diurnal changes in the surface energy balance that directly affect the snow depth, albedo, and surface temperature ultimately affect modeled seasonal ice evolution. Hourly forcing produces earlier onset of snowmelt, and open water duration is increased by 21 days. These differences are due to nonlinearities associated with absorbed shortwave radiation as well as latent and sensible heat fluxes. The accuracy of model parameterizations of downwelling shortwave (K↓) and longwave (L↓) fluxes and albedo over diurnal timescales is assessed by comparison to field observations made during the Seasonal Ice Monitoring and Modeling Site (SIMMS) 1992–1993 field experiments near Resolute Bay, Northwest Territories. Mean K↓ errors (modeled ‐ observed) were −23 W m−2, with a standard deviation of 89 W m−2, and mean L↓, errors were −1 W m−2, with a standard deviation of 18.8 W m−2. Modeled dry/new snow and wet snow albedos were about 0.1 and 0.05, respectively, lower than those observed, allowing greater amounts of shortwave energy absorption into the snowpack. Using SIMMS 1992 on‐ice field data as replacement for model K↓, L↓, and albedo parameterizations shows very different spring period simulations compared with using hourly forcing from Resolute land‐based observations. Simulated net surface flux, surface temperature, and snow‐ice ablation were significantly improved.

Asymmetric late Pleistocene glaciations in the North Basin of the Baikal Rift, Russia

New morphological, sedimentological, and radiocarbon data of Quaternary deposits from the northern Baikal Rift document at least three extensive late Pleistocene glaciations at >50 ka, 40–35 ka, and 26–13 ka, respectively. During these periods valley glaciers advanced from the high rift shoulders (>2500 m) down to the present-day coast of Lake Baikal (456 m); in places, the glaciers advanced beyond the present-day shoreline into the lake basin as indicated by large moraines exposed in steep cliffs along the lakeshore. Furthermore, stratigraphic relations between lacustrine sequences and glacial deposits, as well as 14 C-ages of two palaeo-shorelines 10 and 4 m above the present lake level, show that the last and the penultimate glaciations were followed by relative lake highstands. These land-based observations document a significant influence of late Pleistocene glaciations on the sedimentary development of this lacustrine rift basin. The northern Baikal Rift is characterized by an asymmetric half-graben geometry that controls river drainage and sedimentation. This asymmetry greatly influenced the development and spatial distribution of Pleistocene glaciers on both rift margins. On the western flank, tilted fault blocks parallel to the rift served as topographic barriers for valley glaciers advancing toward the lake basin; only in two locations glaciers could reach the present-day coast. On the eastern rift flank, in contrast, structure and drainage conditions allowed the development of numerous consequent streams providing thoroughfares and space for recurrent valley glaciations. Thus, the glaciers on the eastern flank could advance beyond the present-day lakeshore into the lake basin in numerous locations. These observations indicate that asymmetric rift structure in combination with the effects of global cooling were the important controls on the Pleistocene glacial development of the Baikal Rift.

On the formation of coastal polynyas in the area of Commonwealth Bay, Eastern Antarctica

Antarctica's King George V Land and Adélie Land were first explored by Sir Douglas Mawson and his party during their 1911–1913 expedition. They were astounded by the strength of the katabatic wind, which is so dominant in this area. These strong offshore winds can move the sea ice away from shore, forming coastal polynya, not only in summer but even in midwinter. Poor visibility due to darkness and frequently occurring blowing snow make the study of these polynyas from land-based observations difficult. Recently, coverage of this area by synthetic aperture radar (SAR) satellite imagery, which has a high resolution of 40 m (pixel size 12.5 m), gave additional insight into the characteristics of these polynyas. This high resolution is needed because the width of the polynya is small (10 km or so). Furthermore, of special importance is the fact that SAR data can be obtained during darkness and overcast conditions. Following original Russian work, we modified a simple model for wind-driven coastal polynyas, using actual meteorological data from our coastal automatic weather stations as input. Using mean monthly data for the stations, we show that coastal polynyas are to be expected in the windiest area (Cape Denison-Port Martin); while to the west (Dumont d'Urville) and east (Penguin Point), the average conditions do not produce them. Here, they occur only during strong and long-lasting storms. Our observational data of the polynyas as viewed from SAR and advanced very high resolution radiometer (AVHRR) confirm these findings.

Nutrient and persistent pollutant deposition on the Bothnian Bay ice and snow fields

A study of atmospheric deposited nutrients and some persistent pollutants has been carried out on the ice and snow fields of the subarctic Bothnian Bay, the northernmost basin of the Baltic Sea. Total amounts of 600, 500 and 400 tons NO3-N, NH4-N and Norg-N, respectively are deposited in the snow while the corresponding amounts for Ptot-P is 40 tons. The corresponding amount for PCB and lindane are 1.0 and 0.2 kg, respectively. The measurements were carried out on the snow-covered ice four to six weeks old. A part of the deposited snow has been incorporated -into the snow-ice and an attempt to estimate its mean thickness and its amount of nutrients has been made. The total amounts now reach 1700, 1300 and 1100 tons of NO3-N and NH4-N and Norg-N, respectively in the snow and ice together. The results obtained support the use of land-based stations in estimates of seasonal atmospheric nutrient deposition to the Bothnian Bay. The observed concentrations of chloroorganic compounds correspond to those land-based observations reported from the same latitude in the northern hemisphere and reported in literature.

Abundance and stock composition of narwhals (Monodon monoceros) in lnglefield Bredning (NW Greenland)

The abundance of narwhals (Monodon monoceros) was estimated in Inglefield Bredning (NW Greenland) during the open-water season. Land-based observations were made in August 1985 and 1988 and aerial surveys using line-transect methodology were flown during late August 1985 and early August 1986. Group sizes based on both land-based and aerial surveys are given in relation to behavior and the age and sex composition of groups. The aerial surveys in 1986 indicated that adults comprised about 68%, non-adults (including neonates) 32%, and neonates about 15% of the population present in lnglefield Bredning. On 20 August 1985 a direct land-based count of 1548 whales was obtained in the eastern part of Inglefield Bredning. The aerial surveys in August 1985 resulted in estimates of between 847 (95% Cl 344-2085) and 1366 (95% Cl 854–2276), uncorrected to account for those out of sight underwater.
 The aerial surveys in 1986 resulted in uncorrected estimates of between 2683 (95% CI 1029- 6998) and 4369 (95% CI 2037-9341). Between late July and mid-August 1988, remarkably fewer narwhals were observed from land in the eastern parts of Inglefield Bredning. The maximum number of narwhals that could be accounted for during this period was 473 narwhals.

Asymmetric back-arc spreading, heat flux and structure associated with the Central Volcanic Region of New Zealand

The Central Volcanic Region of New Zealand is an active back-arc basin developed within continental lithosphere, and therefore offers a rare opportunity to study back-arc extension from land-based observations. Two parameters related to the heat output from the Central Volcanic Region are of particular interest. Firstly, the average heat flow for the eastern half of the Central Volcanic Region is about 800 mW/m 2—in order to maintain this heat flow over geological time periods an efficient mass-transfer of heat is required. Secondly, the observed asymmetry in the pattern of heat output, coupled with the tectonic erosion of blocks of continental crust from the eastern axial ranges into the Central Volcanic Region, suggests that the process currently in progress at the eastern margin of the Region is asymmetric spreading with concomitant thermal differentiation of continental crust into its silicic and basic components.

Measurement of declination at South Georgia 1700–1984

ABSTRACTDeclination, or the difference between true and magnetic north, is one of the earliest parameters to have been measured systematically over the earth's surface. Values are available for South Georgia and the surrounding area from 1700 to the present. Observations were made from ship by Edmond Halley in 1700, by James Cook in 1775 and thereafter more frequently. Land-based observations were made during the First Polar Year in 1882–3, more recently by the British Antarctic Survey 1975–82. Declination has diminished from 23°E in 1700 to about 9°W in 1980, approximately 0.1° per annum. The modern observations suggest that the rate of change has slowed in recent years.

Southern Hemisphere Airstream Climatology

Abstract Estimates of mean monthly surface streamlines for the Southern Hemisphere were prepared from gridded mean surface geostrophic winds, from ship and land-based observations collected over several decades. The streamlines were arbitrarily drawn 20° clockwise to the geostrophic direction over oceans, 35° over relatively flat land, and 65° over rough terrain. Except over southern Africa, these assumptions were supported by a comparison between geostrophic directions and those of nearby mean vector winds. Four annual airstream sources were identified within the Southern Hemisphere: one each over the Indian, Pacific, and Atlantic Oceans, and a continental source over Antarctica. A fifth source region was identified over Australia during seven months centered on the Southern winter. Airstreams originating in the Northern Hemisphere penetrate into the Southern Hemisphere during summer, following the Intertropical Zone. During a mean year, 46% of the Southern Hemisphere experiences air originating from onl...

PELAGIC BIRDS AND MAMMALS OF THE SOUTHERN BENGUELA REGION

Summary Research on pelagic birds and mammals in the southern Benguela region has to date concentrated on the breeding species of seabirds and on the Cape fur seal Arctocephalus pusillus. The status of knowledge of non-breeding seabirds and cetaceans is poor to non-existent. Research has so far concentrated on distribution, abundance, diet and land-based observations of breeding biology. Future research should include those species as yet little known and should aim at collecting information which can be used to obtain a real understanding of the relationships between pelagic birds and mammals and their prey within the southern Benguela region. This knowledge should then be used to predict the effect of changes within the system such as those due to the commercial fishery.

Crustal structure in the region of the British Isles

Progress in the application of seismic refraction methods to the determination of crustal structure for the British Isles and surrounding sea areas, is reviewed for the period which follows the publications of 1965. The work has been strongly oriented towards the application of “Time Term” interpretation to land-based observations of explosions in the English Channel, to the south of Ireland, in the Irish Sea, in the North Sea, and off the west coast of Scotland. All of the surveys have included determinations of velocities for P n and P g, with some indication of an increase in P n-velocity with range. In part of the area, indications of lower-crust velocities ranging from 6.9 to 7.3 km/sec have been found.