Bottom Temperature (bottom + temperature)

Distribution by Scientific Domains
Humanities and Social Sciences50%

Selected Abstracts

Spatial distribution and overlap between ichthyoplankton and pelagic fish and squids on the southern flank of Georges Bank

FISHERIES OCEANOGRAPHY, Issue 5 2002
Lance P. Garrison
Abstract We conducted larval and adult fish surveys on the southern flank of Georges Bank during the spring of two years (1990 and 1995) with contrasting physical conditions. We employed canonical correspondence analysis (CCA) to examine the relationships between physical variables and the spatial distribution of pelagic fish and ichthyoplankton. Surface temperature bottom temperature, and vertical stratification were significant factors affecting larval fish distributions, and there were groups of species with similar responses to these variables. There were also consistent relationships between physical variables and pelagic fish and squid abundances and spatial distributions. Pelagic fish and ichthyoplankton with similar responses to hydrographic variables had high spatial overlap, and variation in hydrographic regimes modulated the strength of this interaction. Pelagic fish and squids are potentially important predators of both larval and juvenile fish on Georges Bank. Hydrographic structure modulates the degree of spatial overlap and therefore likely influences the strength of predator,prey interactions. [source]

Talus Instability in a Recent Deglaciation Area and Its Relationship to Buried Ice and Snow Cover Evolution (Picacho Del Veleta, Sierra Nevada, Spain)

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2003
Antonio Gómez
The southernmost glacier in Europe formed during the Little Ice Age at the foot of the north wall of Picacho del Veleta (3 398 m) in Sierra Nevada, in the southeast region of the Iberian Peninsula (lat. 37,03,N, long. 3,22,W). The glacier gradually retreated during the last century, leaving a large talus slope at the base of the wall. The unconsolidated material covering the ice masses acted as a thermal insulator. Recent bottom temperature of snow (BTS) analyses and drillings indicate that the ice still exists within the talus. Evidence from field observations made during the period 1995,2001, revealed that large mass movements occurred during the driest summers (1998 and especially, 1999 and 2000) when the talus was snow free. These conditions suggest a direct relationship between talus stability and thermal insulation from the snow cover in areas where buried ice or decaying marginal permafrost exists. [source]

Geophysical surveys designed to delineate the altitudinal limit of mountain permafrost: an example from Jotunheimen, Norway

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2004
Christian Hauck
Abstract Three geophysical methods have been applied to delineate the altitudinal limit of permafrost at Juvvasshøe/Jotunheimen in southern Norway. By using each method in a complementary way according to its applicability, the permafrost distribution could be analysed on both large and small scales. In addition, temperature-based methods such as the BTS method (bottom temperature of snow cover) were used to validate the results. On a large scale, electromagnetic induction profiling with the EM-31 was used to detect the location of the transition area between frozen and unfrozen ground. Within this area direct-current (DC) resistivity and refraction seismic tomography were also applied to further characterize and visualize the permafrost transition. The large scale surveys revealed a sharp increase in conductivity, indicating an increase in unfrozen water content, near 1400,m a.s.l., with a possible transition zone between 1500,m a.s.l. and 1380,m a.s.l. The small scale investigation delineated the altitudinal limit of permafrost between 1470,m a.s.l. and 1410,m a.s.l., with sporadic ground ice occurrences and temperatures near the freezing point. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Pacific herring, Clupea pallasi, recruitment in the Bering Sea and north-east Pacific Ocean, II: relationships to environmental variables and implications for forecasting

FISHERIES OCEANOGRAPHY, Issue 4 2000
Erik H. Williams
Previous studies have shown that Pacific herring populations in the Bering Sea and north-east Pacific Ocean can be grouped based on similar recruitment time series. The scale of these groups suggests large-scale influence on recruitment fluctuations from the environment. Recruitment time series from 14 populations were analysed to determine links to various environmental variables and to develop recruitment forecasting models using a Ricker-type environmentally dependent spawner,recruit model. The environmental variables used for this investigation included monthly time series of the following: southern oscillation index, North Pacific pressure index, sea surface temperatures, air temperatures, coastal upwelling indices, Bering Sea wind, Bering Sea ice cover, and Bering Sea bottom temperatures. Exploratory correlation analysis was used for focusing the time period examined for each environmental variable. Candidate models for forecasting herring recruitment were selected by the ordinary and recent cross-validation prediction errors. Results indicated that forecasting models using air and sea surface temperature data lagged to the year of spawning generally produced the best forecasting models. Multiple environmental variables showed marked improvements in prediction over single-environmental-variable models. [source]