Last glacial ice‐rafted debris off southwestern Europe: the role of the British–Irish Ice Sheet

Ice‐rafted debris (IRD) seeded into the ocean from Northern Hemisphere ice sheets is found in ocean cores along the southwestern European margin through the last glacial period. It is known that the origin of this IRD, especially off Iberia, can vary between North America and western Europe during short‐lived episodes of greatly enhanced iceberg flux, known as Heinrich events, although in most Heinrich events the IRD has a North American source. During the longer times of much lower IRD fluxes between Heinrich events, use of an intermediate complexity climate model, coupled to an iceberg dynamic and thermodynamic model, shows that background levels of IRD most likely originate from western Europe, particularly the British–Irish Ice Sheet. Combining modelling with palaeoceanographic evidence supports reconstructions of a short‐lived, but substantial, Celtic and Irish Sea Ice Stream around 23 ka. Copyright © 2010 John Wiley & Sons, Ltd.     

An oceanographic survey of the Tasman Front

Results of a detailed expendable bathythermograph survey in the northern Tasman Sea are presented. The Tasman Front, with its origin in the edge of an East Australian Current eddy, extended throughout the survey region. The front marked a coherent, meandering, zonal jet which crosses the Tasman Sea and hence links at least part of the East Australian Current to the other western boundary currents in the subtropical gyre. The frontal meandering derives from both the variability of the East Australian Current system and the topographic effects of the major ridge systems in the north Tasman Sea. The front is less distinct over the crests of these ridges. The flow field in the survey area contained a number of anticyclonic eddies, and current records show that the oceanic eddies are long‐lived features similar to the eddies in the East Australian Current.     

Spatial patterns and environmental drivers of benthic infaunal community structure and ecosystem function on the New Zealand continental margin

To investigate regional drivers of spatial patterns in macro- and meio-faunal community structure (abundance, biomass and taxonomic diversity) and ecosystem function (sediment community oxygen consumption [SCOC]), we sampled two regions in close proximity on New Zealand's continental margin—the Chatham Rise and the Challenger Plateau. Sites (n = 15) were selected in water depths ranging from 266–1212 m to generate a gradient in sedimentary properties and, in particular, surface pelagic productivity. Both macro- and meio-fauna abundance and biomass was 2–3.5 times higher on the Chatham Rise than on the Challenger Plateau, reflecting regional differences in pelagic primary production. We also found significant inter- and intra-regional differences in macro-fauna taxonomic diversity with two distinctive site groupings in each region. Univariate and multivariate measures of macro-fauna community attributes were most strongly correlated with sediment photosynthetic pigment (explaining 24%–59% of the variation). Sediment pigment content was as equally important in explaining meio-fauna community structure (36%–7%). Unlike community structure, SCOC was most strongly correlated with depth (44%), most likely reflecting temperature effects on benthic metabolism. Our results highlight the importance of a benthic labile food supply in structuring infaunal communities on continental margins and emphasise a tight coupling between pelagic and benthic habitats.     

高炮方位标注专利技术的应用

对2007年8月7日发生在太原的突发性暴雨过程,从天气形势、探空资料、多普勒雷达产品等方面进行了分析,结果表明：a）前倾槽、300hPa急流、副高边缘暖湿气流活跃是产生暴雨天气的有利背景。b）探空资料分析表明,中低层暖湿平流、高空干冷平流的存在使得大气层结不稳定趋于增大,是造成此次暴雨的直接原因。c）低层暖平流加辐合和高层辐散叠加的多普勒雷达速度场对大范围强降水发展、维持、消散具有很好的预报指示作用;逆风区、中尺度切变线、辐合线在强降水临近预报中有明确的指示意义。d）雷达风廓线产品分析表明,低空急流在夜间产生并加强,使降水夜间加强并导致大暴雨的发生。     

Transport of Oyashio Water across the Subarctic Front into the Mixed Water Region and Formation of NPIW

Oyashio water flowing into the Mixed Water Region (MWR) and the Kuroshio Extension region that forms North Pacific Intermediate Water (NPIW) has been examined, based on four Conductivity-Temperature-Depth profiler (CTD)/Lowered Acoustic Doppler Current Profiler (L-ADCP) surveys of water masses and ocean currents. There are two processes by which the Oyashio water intrudes across the Subarctic Front (SAF): one is a direct cross-nearshore-SAF transport near Hokkaido along the western boundary, and the other is a cross-offshore-SAF process. Seasonal variations were observed in the former process, and the transport of the Oyashio water across SAF near Hokkaido in the density range of 26.6–27.4σ_θ was 5–10 Sv in spring 1998 and 2001, and 0–4 Sv in autumn 2000, mainly corresponding to the change of the southwestward Oyashio transport. Through the latter process, 5–6 Sv of the Oyashio water was entrained across the offshore SAF from south of Hokkaido to 150° in both spring 2001 and autumn 2000. The total cross-SAF Oyashio water transport contributing to NPIW formation is more than 10 Sv, which is larger than previously reported values. Most of the Oyashio water formed through the former process was transported southeastward through the Kuroshio Extension. It is suggested that the Oyashio intrusion via the latter process feeds NPIW in the northern part of the MWR, mainly along the Subarctic Boundary and SAF. This revised version was published online in July 2006 with corrections to the Cover Date.     

黄河口水下滑坡体系

自１９８８年以来，通过多次野外考察和深入研究，在黄河口发现并确认存在大规模的水下滑坡体系。根据声纳图象和浅地层剖面记录，对滑坡进行分类命名和特征分析。研究表明，该滑坡体系中存在瓶颈状滑坡、平移板状滑坡和旋转滑坡３种类型；许多单个滑坡在下坡方向汇集成复合滑坡系统，有时数十条滑坡汇集成蜿蜒数公里的大规模复杂体系。滑坡冲沟分布广泛，将底坡表层切割得支离破碎，与密西西比河口比较，黄河口水下滑坡具有高含水、     

Recent changes of the thermohaline circulation in the subpolar North Atlantic

Time series of hydrographic sections in the northern North Atlantic from the period 1990 to 2004 are analyzed for changes in the characteristics and distribution of water masses that are involved in the thermohaline circulation (THC). During the 1990s, the North Atlantic Oscillation (NAO) alternates from a positive phase (strong westerlies) to a negative phase (weak westerlies). The reduced ocean heat loss confined the convection in the Labrador Sea to the upper 1,200 m, generating a new salinity minimum layer characterizing the Upper Labrador Sea Water (ULSW), and led to a warming and salinization of the older LSW below due to lateral mixing. The Lower LSW, formed in the first half of the 1990s, spread in the subpolar gyre and reached the Newfoundland and Irminger basins after about 1 to 2 years, where the associated isopycnal doming contributed to eastward frontal shifts in the upper layer. After 5 and 6 years, it arrived in the Iceland and West European basins, respectively. The collapse of the isopycnal dome in the Labrador Sea, associated with the drainage of the Lower LSW, resulted in a slowing of the cyclonic circulation of the subpolar gyre. This was accompanied in the upper layer by a westward shift of the southeastern extension of the gyre and a northward advection of warm and saline subtropical water in its eastern part, which finally reached the Labrador Sea after about 7 years. In the upper layer of the Labrador Sea, the advection of warm and saline water dominated over the heat loss to the atmosphere and the freshwater gain from melting ice and precipitation in the NAO-low period, so that no accumulation of freshwater but an increase of the heat and salt contents were observed, as in the whole eastern part of the subpolar gyre. Within 1 to 2 years after the drop of the NAO in the winter of 1995/1996, the Subarctic (Subpolar) Front shifted northward and westward north of about 50°N, favored by the retreat of the low-salinity tongue extending eastward from the southern Labrador Sea, and it shifted southward and eastward in the Newfoundland Basin. Therefore, the enhanced northward advection of subtropical waters in the northeastern North Atlantic is balanced by the enhanced southward advection of subarctic waters, including Lower LSW in the Newfoundland Basin, indicating a strong response of the gyre component of the THC.     

Photogrammetric Analysis of Front Range Rock Glacier Flow Rates

Flow rates for rock glaciers in the European Alps have been monitored using photogrammetric techniques; however, a program has not been initiated for similar Front Range, USA, rock glaciers. Horizontal rock glacier displacements were measured by tracking large surficial rocks on temporal orthophotos from 1978, 1990, and 1999. Vertical change was measured by creating digital elevation models (DEMs) from digital stereopairs, then subtracting elevations to detect change. Long‐term horizontal velocities ranged from 14 to 20 cm/yr on average, although uncertainty ranged from 4 to 5 cm/yr. On average, vertical elevation changes were negligible with most rock glaciers exhibiting a slight growth or thinning (1–2 cm/yr). Over shorter time scales (c. 10‐year periods), horizontal velocities have only increased by about 2 cm/yr. Because horizontal and vertical change is minimal, Front Range rock glaciers appear to be adjusted with current climate, unlike some rock glaciers in the European Alps that have shown increasing subsidence rates or significant increasing or decreasing horizontal velocities.     

Integrating soils and geomorphology in mountains—an example from the Front Range of Colorado

Soil distribution in high mountains reflects the impact of several soil-forming factors. Soil geomorphologists use key pedological properties to estimate ages of Quaternary deposits of various depositional environments, estimate long-term stability and instability of landscapes, and make inferences on past climatic change. Once the influence of the soil-forming factors is known, soils can be used to help interpret some aspects of landscape evolution that otherwise might go undetected.The Front Range of Colorado rises from the plains of the Colorado Piedmont at about 1700 m past a widespread, dissected Tertiary erosion surface between 2300 and 2800 m up to an alpine Continental Divide at 3600 to over 4000 m. Pleistocene valley glaciers reached the western edge of the erosion surface. Parent rocks are broadly uniform (granitic and gneissic). Climate varies from 46 cm mean annual precipitation (MAP) and 11 °C mean annual temperature (MAT) in the plains to 102 cm and −4 °C, respectively, near the range crest. Vegetation follows climate with grassland in the plains, forest in the mountains, and tundra above 3450 m. Soils reflect the bioclimatic transect from plains to divide: A/Bw or Bt/Bk or K (grassland) to A/E/Bw or Bt/C (forest) to A/Bw/C (tundra). Corresponding soil pH values decrease from 8 to less than 5 with increasing elevation. The pedogenic clay minerals dominant in each major vegetation zone are: smectite (grassland), vermiculite (forest), and 1.0–1.8 nm mixed-layer clays (tundra). Within the lower forested zone, the topographic factor (aspect) results in more leached, colder soils, with relatively thin O horizons, well-expressed E horizons and Bt horizons (Alfisols) on N-facing slopes, whereas soils with thicker A horizons, less developed or no E horizons, and Bw or Bt horizons (Mollisols) are more common on S-facing slopes. The topographic factor in the tundra results in soil patterns as a consequence of wind-redistributed snow and the amount of time it lingers on the landscape. An important parent material factor is airborne dust, which results in fine-grained surface horizons and, if infiltrated, contributes to clay accumulation in some Bt horizons. The time factor is evaluated by soil chronosequence studies of Quaternary deposits in tundra, upper forest, and plains grassland. Few soils in the study area are >10,000 years old in the tundra, >100,000 years old in the forest, and >2 million years old in the grassland. Stages of granite weathering vary with distance from the Continental Divide and the best developed is grus near the sedimentary/granitic rock contact just west of the mountain front. Grus takes a minimum of 100,000 years to form.Some of the relations indicated by the soil map patterns are: (1) parts of the erosion surface have been stable for 100,000 years or more; (2) development of grus near the mountain front could be due in part to pre-Pennsylvanian weathering; (3) a few soil properties reflect Quaternary paleoclimate; and (4) a correlation between soil development in the canyons and stream incision rates.