173,986 research outputs found
Reconstructing Loch Lomond Stadial Glaciers and Climate in the south-west English Lake District
No full textThe most recent glaciation of the English Lake District occurred during the Loch Lomond Stadial (Younger Dryas) when full glacial conditions returned to the British Isles. The largest ice mass formed over the Western Scottish Highlands with smaller ice masses developing throughout the British uplands.
In the Lake District, our understanding of the extent and timing of the Loch Lomond Stadial glaciation is patchy and poorly constrained by geochronology. Sissons (1980) proposed the development of 64 independent alpine-style ice masses in the district during the Loch Lomond Stadial. The location and geometry of these ice masses showed some agreement to the earlier, but coarser scale, map of ice masses produced Manley (1959) for the same period, however some significant differences were also apparent. More recently, McDougall (1998: 2001) has proposed the development of plateau icefields in the Lake District centred over High Raise, Grey Knotts/Dale Head, Brandreth and Kirk Fell. This much more extensive style of glaciation involved 40-50 m of cold based non-erosive ice occupying the plateau summits and feeding down into warm-based geomorphologically active outlet glaciers in the valleys. Further Loch Lomond Stadial sites have also been identified in the Lake District by Wilson (2002: 2004) and Wilson and Clark (1998: 1999).
The geomorphology of the south-west Lake District is identified and presented here and glaciers are then reconstructed based upon this evidence. Palaeoclimatic inferences made based upon the reconstructed glacial extent vary greatly depending on the style of glaciation that occurred during Stadial (alpine or plateau icefield). Of particular note, plateau icefields have the potential to significantly raise the equilibrium line altitude (ELA) across a region. This lowers the temperature at the ELA and therefore increases the reconstructed palaeoprecipitation at the ELA. In order to test the viability of the reconstructed glaciers in the Lake District, a 2D velocity-mass balance model is applied to the glaciers (adapted from Carr and Coleman,2007). This model assumes that where a glacier is glaciologically viable under the parameters used to drive the model, the basal velocity (Ub) accounts for < 90 % of the surface velocity in the centre of the channel (Us).
Further mass contributions to the glaciers via mechanisms such as snowblow are quantified using a revised definition of potential snowblow areas. The significance of these areas is then assessed with respect to the ELA of the glaciers. Digitisations of the work of Sissons (1980), McDougall (1998), Wilson and Clark (1998: 1999) in the Lake District are then presented and compiled with the work of the current author to illustrate the extent of the Loch Lomond Stadial throughout the whole district
The food and feeding of powan Coregonus lavaretus (L.) (Salmonidae: Coregoninae) in two Scottish lochs
No full textThe present study is mainly a descriptive account of the food and
feeding of the two Scottish powan populations from Loch Lomond and
Loch Eck. Quantitative and qualitative comparisons of powan diet are
made. Seasonal variations of diet are determined for the two
populations and some aspects of the planktivorous feeding of adult
pawan in Loch Lomond are examined. The partitioning of the ingested
energy into somatic and non-somatic growth is considered. Factors
affecting the feeding of the two populations are discussed
High-precision radiocarbon dating of the construction phase of Oakbank Crannog, Loch Tay, Perthshire
No full textMany of the Loch Tay crannogs were built in the Early Iron Age and so calibration of the radiocarbon ages produces
very broad calendar age ranges due to the well-documented Hallstatt plateau in the calibration curve. However, the
large oak timbers that were used in the construction of some of the crannogs potentially provide a means of improving the precision of the dating through subdividing them into decadal or subdecadal increments, dating them to high precision and wiggle-matching the resulting data to the master <sup>14</sup>C calibration curve. We obtained a sample from 1 oak timber from Oakbank Crannog comprising 70 rings (Sample OB06 WMS 1, T103) including sapwood that was complete to the bark edge. The timber is situated on the northeast edge of the main living area of the crannog and as a large and strong oak pile would have been a useful support in more than 1 phase of occupation and may be related to the earliest construction phase of the site. This was sectioned into 5-yr increments and dated to a precision of approximately ±8–16 <sup>14</sup>C yr (1 σ). The wiggle-match predicts that the last ring dated was formed around 500 BC (maximum range of 520–465 BC) and should be taken as indicative of the likely time of construction of Oakbank Crannog. This is a considerable improvement on the estimates based on single <sup>14</sup>C ages made on oak samples, which typically encompassed the period from around 800–400 BC
Cryptosporidiosis and filtration of water from Loch Lomond, Scotland
No full textPrevious evidence has suggested an association between consumption of unfiltered water from Loch Lomond, Scotland, and cryptosporidiosis. Before November 1999, this water had been only microstrained and disinfected with chlorine; however, since that time, physical treatment of the water (coagulation, rapid gravity filtration) has been added. To determine risk factors, including drinking water, for cryptosporidiosis, we analyzed data on laboratory-confirmed cases of cryptosporidiosis collected from 1997 through 2003. We identified an association between the incidence of cryptosporidiosis and unfiltered drinking water supplied to the home. The association supports the view that adding a filtration system to minimally treated water can substantially reduce the number of confirmed cryptosporidiosis cases
Growth processes in the two Scottish populations of powan, Coregonus lavaretus (L.) (Eateleosteia, Salmonidae)
No full textThe powan, Coregonus lavaretus (L.) is endemic to only two
British waters, Loch Lomond and Loch Eck, Scotland. This
thesis describes the seasonal and longer term growth
processes of the two populations, concentrating on growth in
length back-calculated from scales, factors affecting
recruitment and mortality, reproductive cycles, and seasonal
deposition and mobilisation of storage products,
particularly lipid. The interrelationships of these cycles
is discussed. The populations differ in their diet and
duration of feeding, and it is shown that most of the inter-population differences in seasonal cycles of growth relate
to these feeding differences. The Loch Eck population is the
more variable. In addition to adult and immature powan, a
third category is identified, termed adolescents. These are
fish which are entering their first reproductive cycle.
Immature and adolescent fish are analysed separately and
compared with the adults. There are some differences in
seasonal cycles between the juveniles and adults, mainly in
relation to the presence or absence of the reproductive
cycle. A preliminary histological study of the ovaries of
adolescent females is carried out. Comparison of historical
data with the results of the present study shows that there
has been little change in the Loch Lomond powan in the past
200 years. Both lochs are coming under increasing human
pressure, and conservational measures urgently need to be
taken if the powan populations are to survive
The physiology of the reproductive cycle of the powan of Loch Lomond, Coregonus lavaretus (L) (Euteleostei, Salmonidae) in relation to the deposition and mobilization of storage products
No full textThere have been
numerous studies
in
which
the
reproductive
cycles of
teleosts have been
correlated with either environmental
cycles or associated physiological cycles, or
both. Such
correlation
is
seldom accurately achieved; usually
because the
reproductive cycle
of
the
species concerned
is lax,
sometimes
because
only one or
two
factors
of an
integrated
whole were examined.
The
powan of
Loch Lomond, Coregonus lavaretus
(L. ) (Teleostei,
Salmoniformes) is the
subject of a
long-term
study
investigating its
growth,
in particular reproduction.
This
race
is
a
freshwater
glacial
relict
form
of a
boreal
group, and
thus has
an exceptionally strictly
times
reproductive cycle.
It thus
represents an
ideal
subject for
cyclical studies.
This thesis investigates the
relationship between
lipid
storage
and
the
reproductive cycle and
the
role of
thyroid
gland
The Devensian Lateglacial and early Flandrian stratigraphy of Southern Snowdonia, North Wales.
No full textPhDThe Devensian Lateglacial and early Flandrian stratigraphy of southern Snowdonia,
North Wales has been examined using pollen analytical, radiocarbon dating and geomorphological
mapping techniques. These techniques were used to reconstruct the effects and timing of
environmental changes on the Lateglacial and early Flandrian vegetation and landscape.
Detailed geomorphological mapping enabled the reconstruction of former "cwm" glaciers
and snowpatches of inferred Loch Lomond (Younger Dryas) Stadial age. These former glaciers were
small and extremely localised, their distribution being influenced by altitude, aspect and snowdrift A
local equilibrium fim line of 600 m OD was estimated from former glaciers on Cader Idris and used
to infer a mean July temperature of 8.5 ' C at sea-level during the Stadial. Pollen analyses of three
mire sites located outside the former ice limits and three upland lake sites from inside the limits
helped to corroborate a Loch Lomond (Younger Dryas) Stadial age for the "cwm" glaciation.
Logistical problems of sampling upland lake sites were overcome by the innovative use of sub-aqua
divers.
An exceptionally thick sequence of Lateglacial and early Flandrian organic-rich
sediments was discovered at Llyn Gweman and provided a particularly high degree of stratigraphic
resolution for radiocarbon dating vegetational changes and other environmental events. Late
Devensian ice was shown to have abandoned the Llyn Gwernan site before ca.13,200 BP at which
time the landscape was rapidly colonised by a pioneer vegetation in which Rumex was prominent.
Juniper spread into the area at ca.13,000 BP and was succeeded by the expansion of birch woodland
at ca.12,100 BP. Gradual climatic deterioration was inferred from this time onward, culminating in
the revertence to a tundra-like environment during the Loch Lomond (Younger Dryas) Stadial, hereby
dated to between ca.11,200 BP and 10,000 BP. The climate improved at around 10,000 BP and
vegetational succession progressed from herb-rich grassland, through expansion phases for juniper,
willow, birch and eventually hazel at ca.9,100 BP
Changes in gene expression, lipid class and fatty acid composition associated with diapause in the marine copepod Calanus finmarchicus from Loch Etive, Scotland.
No full textZooplankton are the major primary consumers in pelagic ecosystems, providing the principal pathway for energy transfer from primary production to higher trophic levels. The marine copepod Calanus finmarchicus is an important component of the pelagic food web in the North Atlantic and peripheral ecosystems, and forms an essential dietary component of a number of commercially important fish. As part of its life cycle, many C. finmarchicus overwinter in a diapause phase (a dormant overwintering phase where development is suppressed in adaptation to the seasonal food supply) at depths of 500 to 2000 m, but little is known about the triggers that initiate and terminate diapause, or the internal processes associated with these triggers. Understanding these processes is important, given that subtle changes in the environmental conditions which may affect diapause could have consequences for the entire Calanus-based ecosystem. In this study I took advantage of relatively easy access to a deep (> 100 m), isolated population of C. finmarchicus in Loch Etive (a sea loch on the west coast of Scotland) to sample Calanus finmarchicus monthly between April 2006 and June 2007 and measure lipid dynamics and gene expression associated with diapause. Chapter 1 of this thesis provides a general introduction to diapause and Calanus finmarchicus, Chapter 2 reports on the population of C. finmarchicus in Loch Etive, Chapter 3 reports changes in the lipid class and fatty acid composition of individual copepods, Chapter 4 reports on differential gene expression between diapausing and active C. finmarchicus and Chapter 5 provides a general discussion and puts this research into context. This study provides some initial insight into possible gene expression patterns, but further work is needed to attribute specific gene expression patterns with initiation and termination of diapause
[Letter] 1849 January 28 [to] James Loch / Spencer [Frederick Spencer, 4th Earl].
No full textThe letter is addressed from Althorp, the home of the Spencer family for 500 years; a memorial to Diana, Princess of Wales is located at the site in Northamptonshire, not far from London. For more information on the Spencer family or their estate, visit their website (http://www.althorp.com/home/index.asp). See also other letters in the collection from John Charles Spencer, 3rd Earl, and George John Spencer, 2nd Earl.Spencer writes that he shall be glad to consider the testimonials of Captain Pearson as well as Loch\u27s interest in his success. He says that he must however "guard myself from giving any promise of support" as he has determined to adopt a course which leave him free on the day of election to choose among the number of candidates. The most well-known member of the 20th c. Spencer family was Diana Spencer, later Princess of Wales. James Loch (1780-1855) was an economist
Scottish late-glacial moraines: debris supply, genesis and significance
No full textA variety of moraine forms were deposited by glaciers during the
Loch Lomond Stadial. Study of such moraines and related landforms
provides a valuable source of data on patterns of landscape evolution
and climatic change. This thesis presents detailed case-studies of
moraines in geologically and topographically contrasting areas on the
Island of Skye, Scotland. Geomorphological mapping,
sedimentological analyses and mathematical modelling techniques
were employed to determine the principal controls on moraine
morphology, composition and distribution. Particular emphasis was
placed on the provenance, transport and deposition of debris, and
their spatial variation. The results were used to construct a summary
model of glacial landform evolution, which relates different
sediment-landform associations to spatial and temporal controls,
particularly basin lithology and structure, topography, position of
deposition and ice-margin activity.
The initial stage of deglaciation in the study area was marked by a
series of readvances and/or stillstands. During this stage, the
lower-lying glaciers were more sensitive to climatic amelioration
than the higher glaciers. The subsequent phase was characterised by
more rapid deglaciation. Evidence for one instance of late-stage in
situ glacier stagnation is described. The results indicate that
landforms hitherto grouped as 'hummocky -moraine' formed by a
variety of processes. Such moraines formed by (a) uneven deposition
of supraglacially and/or -subglacially-derived debris at active ice
margins, (b) deposition at the stagnant margins of otherwise active
glaciers, and (c) deposition during uninterrupted glacier retreat or
areal stagnation. Differentiation and analysis of so-called 'hummocky
moraine' enables glacier behaviour, during the Lateglacial to be
interpreted in great detail
- …
