John Fyfe

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Papers by John Fyfe

Cubilin expression and posttranslational modification in the canine gastrointestinal tract

American Journal of Physiology Gastrointestinal and Liver Physiology, Oct 1, 2000

Cubilin is an endocytic receptor of the apical brush border membrane that is essential for intrin... more Cubilin is an endocytic receptor of the apical brush border membrane that is essential for intrinsic factor-mediated cobalamin absorption in small intestine. However, cubilin is more highly expressed in kidney and yolk sac, and recent molecular characterization of the receptor has focused on these tissues. The aim of this investigation was to examine tissue-specific cubilin expression and posttranslational modifications with an emphasis on the gastrointestinal tract. Intrinsic factor-cobalamin binding activity, cubilin immunoreactivity, and cubilin mRNA levels were determined in multiple segments of canine gastrointestinal mucosa and other tissues. These aspects of cubilin expression varied in parallel, suggesting that the major determinant of regional cubilin expression in the gastrointestinal tract is modulation of cubilin mRNA. Cell fractionation indicated that ileal cubilin is not strongly membrane associated. An approximately 185-kDa brush border specific and two &gt;400-kDa precursor forms of cubilin were identified. Asparagine-linked oligosaccharide modifications characterized by differential glycosidase digestion of affinity-purified cubilin from ileal mucosa and renal cortex differed, but ileal and renal intracellular cubilin comigrated on SDS-PAGE at approximately 400 kDa after oligosaccharide removal, thus reconciling previous conflicting size estimates of the cubilin polypeptide.

Genetic evidence of an accessory activity required specifically for cubilin brush-border expression and intrinsic factor-cobalamin absorption

Blood, Nov 15, 1999

Cubilin is a high molecular weight multiligand receptor that mediates intestinal absorption of in... more Cubilin is a high molecular weight multiligand receptor that mediates intestinal absorption of intrinsic factor-cobalamin and selective protein reabsorption in renal tubules. The genetic basis of selective intestinal cobalamin malabsorption with proteinuria was investigated in a canine model closely resembling human Imerslund-Grä sbeck syndrome caused by cubilin mutations. Canine CUBN cDNA was cloned and sequenced, showing high identity with human and rat CUBN cDNAs. An intragenic CUBN marker was identified in the canine family and used to test the hypothesis of genetic linkage of the disease and CUBN loci. Linkage was rejected, indicating that the canine disorder resembling Imerslund-Grä sbeck syndrome is caused by defect of a gene product other than cubilin. These results imply that there may be locus heterogeneity among human kindreds with selective intestinal cobalamin malabsorption and proteinuria and that normal brush-border expression of cubilin requires the activity of an accessory protein.

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Failure to thrive and life-threatening complications due to inherited selective cobalamin malabsorption effectively managed in a juvenile Australian shepherd dog

The Canadian veterinary journal. La revue vétérinaire canadienne, 2015

A juvenile Australian shepherd dog exhibited failure to grow, inappetence, weakness, nonregenerat... more A juvenile Australian shepherd dog exhibited failure to grow, inappetence, weakness, nonregenerative anemia, neutropenia, and cobalamin deficiency. DNA testing confirmed homozygosity of an amnionless mutation (AMN c.3G > A). Clinical signs resolved with supportive care and parenteral cobalamin supplementation. Inherited selective intestinal cobalamin malabsorption requiring lifelong parenteral supplementation should be considered in Australian shepherds, giant schnauzers, border collies, and beagles that fail to thrive.

Large near-term projected snowpack loss over the western United States

Nature communications, Jan 18, 2017

Peak runoff in streams and rivers of the western United States is strongly influenced by melting ... more Peak runoff in streams and rivers of the western United States is strongly influenced by melting of accumulated mountain snowpack. A significant decline in this resource has a direct connection to streamflow, with substantial economic and societal impacts. Observations and reanalyses indicate that between the 1980s and 2000s, there was a 10-20% loss in the annual maximum amount of water contained in the region's snowpack. Here we show that this loss is consistent with results from a large ensemble of climate simulations forced with natural and anthropogenic changes, but is inconsistent with simulations forced by natural changes alone. A further loss of up to 60% is projected within the next 30 years. Uncertainties in loss estimates depend on the size and the rate of response to continued anthropogenic forcing and the magnitude and phasing of internal decadal variability. The projected losses have serious implications for the hydropower, municipal and agricultural sectors in the ...

The Antarctic Sea Ice Response to the Ozone Hole in Climate Models

Http Dx Doi Org 10 1175 Jcli D 13 00590 1, Jan 24, 2014

On the response of the oceanic wind-driven circulation to atmospheric CO 2 increase

Clim Dynam, 2005

A global, flux-corrected climate model is employed to predict the surface wind stress and associa... more A global, flux-corrected climate model is employed to predict the surface wind stress and associated wind-driven oceanic circulation for climate states corresponding to a doubling and quadrupling of the atmospheric CO 2 concentration in a simple 1% per year CO 2 increase scenario. The model indicates that in response to CO 2 increase, the position of zero wind stress curl in the mid-latitudes of the Southern Hemisphere shifts poleward. In addition, the wind stress intensifies significantly in the mid-latitudes of the Southern Hemisphere. As a result, the rate of water circulation in the subpolar meridional overturning cell in the Southern Ocean increases by about 6 Sv (1 Sv=10 6 m 3 s À1 ) for doubled CO 2 and by 12 Sv for quadrupled CO 2 , implying an increase of deep water upwelling south of the circumpolar flow and an increase of Ekman pumping north of it. In addition, the changes in the wind stress and wind stress curl translate into changes in the horizontal mass transport, leading to a poleward expansion of the subtropical gyres in both hemispheres, and to strengthening of the Antarctic Circumpolar Current. Finally, the intensified near-surface winds over the Southern Ocean result in a substantial increase of mechanical energy supply to the ocean general circulation.

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Separating Extratropical Zonal Wind Variability and Mean Change

Journal of Climate, Mar 1, 2003

Changes in the naturally occurring modes of extratropical annual mean and zonal mean zonal wind v... more Changes in the naturally occurring modes of extratropical annual mean and zonal mean zonal wind variability are investigated using National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalyses and Canadian Centre for Climate Modelling and Analysis (CCCma) global climate model simulations. In the Northern Hemisphere, the first and second modes are primarily stratospheric and tropospheric in character, respectively. The surface pressure manifestations of these modes are intimately linked to the Arctic Oscillation (AO), and together suggest separate stratospheric and tropospheric origins for the AO. In the Southern Hemisphere, the first mode describes north-south shifts in the polar front jet accompanied by polar stratospheric jet fluctuations and Antarctic Oscillation (AAO)-like surface pressure anomalies. The second mode is primarily tropospheric and describes interannual changes in the strength and position of the polar front jet.The leading observed modes appear unchanged in strength since the 1950s except in the Northern Hemisphere where the second mode shows some evidence of increasing strength. The leading simulated modes appear unchanged in strength since the beginning of the twentieth century, and are predicted to remain so to the end of the twenty-first century. In all cases the leading modes are superimposed upon significant mean change, which when not properly accounted for can lead to erroneous conclusions.

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Extratropical Storms and Climate Change: Recent Results and Emerging Questions

Agu Fall Meeting Abstracts, Dec 1, 2005

The effect of enhanced greenhouse warming on extratropical (including Arctic and Sub-Arctic) stor... more The effect of enhanced greenhouse warming on extratropical (including Arctic and Sub-Arctic) storms is examined for changes in the total number of storms, and for changes in the number of intense storms, using output from the coupled climate models participating in the IPCC AR4 diagnostic exercise. For the past and present centuries the models simulate a reduction in the total number of storms and an increase in the number of intense storms - with the 20th century changes being consistent with observations. These are robust results, which essentially all the models exhibit. Some emerging questions to be highlighted in this presentation include: 1) Why are there opposing changes in storminess frequency and intensity?; 2) How do circulation changes (say, associated with the Annular Modes) affect storminess? and 3) How reliable are coupled climate model predictions over the Arctic and Sub-Arctic regions where well-known circulation biases prevail?

Estimating the Anthropogenic Sea Surface Temperature Response Using Pattern Scaling

Http Dx Doi Org 10 1175 Jcli D 14 00604 1, May 1, 2015

This study seeks to derive the sea surface temperature (SST) response to anthropogenic forcing fr... more This study seeks to derive the sea surface temperature (SST) response to anthropogenic forcing from observations over the last century, using simple methods inspired from pattern scaling. As in pattern scaling, the spatial response is assumed to scale with global-mean and annual-mean surface temperature. The long-term aim of this work is to generate anthropogenically forced SST and sea ice patterns for the recent past and nearterm future, and use them to force atmosphere-land climate models for attribution and prediction purposes. The present work compares estimation methodologies and, within a Monte Carlo framework based on large initial condition ensembles of climate model simulations, examines the robustness of the patterns obtained.

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Enhanced climate change and its detection over the Rocky Mountains

Journal of Climate, 1999

Results from an ensemble of climate change experiments with increasing greenhouse gas and aerosol... more Results from an ensemble of climate change experiments with increasing greenhouse gas and aerosols using the Canadian Centre for Climate Modelling and Analysis Coupled Climate Model are presented with a focus on surface quantities over the Rocky Mountains. There is a marked elevation dependency of the simulated surface screen temperature increase over the Rocky Mountains in the winter and spring seasons, with more pronounced changes at higher elevations. The elevation signal is linked to a rise in the snow line in the winter and spring seasons, which amplifies the surface warming via the snow-albedo feedback. Analysis of the winter surface energy budget shows that large changes in the solar component of the radiative input are the direct consequence of surface albedo changes caused by decreasing snow cover.Although the warming signal is enhanced at higher elevations, a two-way analysis of variance reveals that the elevation effect has no potential for early climate change detection. In the early stages of surface warming the elevation effect is masked by relatively large noise, so that the signal-to-noise ratio over the Rocky Mountains is no larger than elsewhere. Only after significant continental-scale warming does the local Rocky Mountain signal begin to dominate the pattern of climate change over western North America (and presumably also the surrounding ecosystems and hydrological networks).

The Southern Ocean response to poleward intensifying winds: a model resolution sensitivity study

Agu Fall Meeting Abstracts, Dec 1, 2007

The Antarctic Circumpolar Current (ACC) connects all the major ocean basins, has the highest volu... more The Antarctic Circumpolar Current (ACC) connects all the major ocean basins, has the highest volume transport in the world ocean and plays a key role in global climate. Observational records and modeling results indicate a consistent poleward intensification of the zonal wind stress over the Southern Ocean concomitant with anthropogenic warming through the 20th and 21st centuries. Coarse resolution global model studies, with simple geostrophic balance considerations, have shown an increase in transport and poleward shift in the position of the ACC in response to the changing winds. However, regional eddy-permitting models identified changes in the intensity of the eddy field but little change in ACC transport (an effect dubbed "eddy saturation"). In this study, versions of a global climate model with horizontal resolutions ranging from 1.8 x 3.6 (degrees) to 0.2 x 0.4 are used to refine our understanding of anthropogenically induced changes in Southern Ocean. The models are forced time-varying Southern Ocean surface wind anomalies through the 21st century. The effect of model resolution on the response of Southern Ocean heat content, volume transport, eddy kinetic energy and heat transport will be discussed.

Sea Ice Response to Wind Forcing from AMIP Models

Journal of Climate, Mar 1, 2002

The Arctic surface circulation simulated by atmospheric general circulation models is assessed in... more The Arctic surface circulation simulated by atmospheric general circulation models is assessed in the context of driving sea ice motion. A sea ice model is forced by geostrophic winds from eight models participating in the first Atmospheric Model Intercomparison Project (AMIP1), and the results are compared to simulations with the sea ice model forced by observed winds. The mean sea level pressure in the AMIP models is generally too high over the Arctic Ocean, except in the Beaufort and Chukchi Seas, where it is too low. This pattern creates anomalous winds that tend to transport too much ice away from the coast of Greenland and the Canadian Archipalego, and into the East Siberian Sea, producing a pattern of ice thickness in the Arctic that is rotated by roughly 180° relative to what is expected based on observations. AMIP winds also drive too little ice transport through Fram Strait and too much transport east of Svalbard by way of the Barents Sea. These errors in ice thickness and transport influence ice growth and melt rates and hence the freshwater flux into the ocean. Sensitivity experiments that test the model response to the wind composition show the ice thickness patterns depend primarily on the climatological mean annual cycle of the geostrophic winds. Daily wind variability is necessary to create sufficient ice deformation and open water, but the sea ice behavior is rather insensitive to the details of the daily variations.

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On Annular Modes and Zonal Jets

Journal of Climate, May 1, 2008

This study considers the relation of the annular mode to the kinematics of a fluctuating jet in z... more This study considers the relation of the annular mode to the kinematics of a fluctuating jet in zonal-mean zonal wind and to the zonal index, using an idealised model of fluctuations in the eddy-driven jet. When the sphericity of the domain is accounted for, observed and numerically simulated annular modes for the Southern Hemisphere summertime are found to be in excellent agreement. In particular, the annular mode and zonal index mode are shown to be related but distinct. Although the annular mode is strongly (but not identically) related to fluctuations in jet position, fluctuations in jet strength and width are shown to also be important for its simulation. When the sphericity of the domain is neglected, analytic expressions for the leading Empirical Orthogonal Function (EOF) modes of zonal-mean geopotential for the cases of individual fluctuations in jet strength, position, and width can be obtained. None of these EOF modes have the characteristics of the annular mode. In the presence of simultaneous fluctuations in jet strength and position, the leading zonal-mean geopotential EOF mode (strongly resembling the annular mode) is shown to mix the zonal index mode of zonal-mean zonal wind with other EOF modes, demonstrating why the annular mode and zonal index mode are related but distinct. The greater sensitivity to domain size of EOF modes of geopotential relative to the EOF modes of zonal-mean zonal wind is also discussed. This study focuses on the Southern Hemisphere summertime, which is characterised by a single, eddy-driven jet; the generality of the results presented suggest that the conclusions should be qualitatively unchanged in the presence of both subtropical and eddy-driven jets.

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Extratropical Southern Hemisphere Cyclones: Harbingers of Climate Change?

J Climate, 2003

In concert with a poleward shift in baroclinicity, the synoptic environment south of 40°S appears... more In concert with a poleward shift in baroclinicity, the synoptic environment south of 40°S appears to have changed significantly over recent decades. South of 40°S and north of the Antarctic Ocean the number of cyclones has dramatically decreased, while over the Antarctic Ocean a modest increase has occurred. A global climate model with anthropogenic forcing produces similar historical changes, and under a `business-as-usual' emissions scenario predicts that the number of sub-Antarctic Ocean cyclones will drop by over 30% between now and century's end.

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Simulated changes in the extratropical Southern Hemisphere winds and currents

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The Arctic and Antarctic Oscillations and their Projected Changes Under Global Warming

The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) are the leading modes of high-lat... more The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) are the leading modes of high-latitude variability in each hemisphere as characterized by the first EOF of mean sea-level pressure. Observations suggest a recent positive trend in the AO and it is speculated that this may be related to global warming. The CCCma coupled general circulation model control simulation exhibits a robust and realistic AO and AAO. Climate change simulations for the period 1900-2100, with forcing due to greenhouse gases and aerosols, exhibit positive trends in both the AO and the AAO. The model simulates essentially unchanged AO/AAO variations superimposed on a forced climate change pattern. The results do not suggest that a simulated trend in the AO/AAO necessarily depends on stratospheric involvement nor that forced climate change will be expressed as a change in the occurence of one phase of the AO/AAO over another. This pattern of climate change projects exclusively on the AAO pattern in the southern hemisphere but not in the northern hemisphere where other EOFs are involved. The extent to which this forced climate change pattern and the unforced modes of variation are determined by the same mechanisms and feedbacks remains an open question.

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On the role of the unresolved eddies in a model of the residual currents in the central strait of Georgia, B.C.: Research Note

Atmos Ocean, 1995

ABSTRACT

Characterizing zonal wind variability: Lessons from a simple GCM

The Coupled Patterns between Sea Level Pressure and Sea Surface Temperature in the Midlatitude North Atlantic

Journal of Climate, Aug 1, 1996

Monthly variability of atmosphere-ocean interactions in the midlatitude North Atlantic during the... more Monthly variability of atmosphere-ocean interactions in the midlatitude North Atlantic during the winter months (November-April) is examined. Composite and singular value decomposition (SVD) analyses are applied to the observed sea level pressure (SLP) and sea surface temperature (SST) anomalies of each winter month for the period 1950-1987. The SLP anomaly composites (i.e., SLP differences between selected warm and cold SST months) are constructed based on the averaged SST anomalies over the RM region (60°-40°W and 50°-40°N). These composites shift from a positive monopole pattern in early winter to a dipole pattern in midwinter and then back to a monopole pattern in late winter.A complementary SVD analysis reveals that the first SVD mode is dipole structured and especially dominant in midwinter. The second SVD mode is monopole featured and more dominant in early and late winter than in midwinter. By examining the spatial distributions of the SVD modes and especially their similarities to the patterns derived from other model simulations, two coupling processes are suggested. The dipole mode is suggested to be related to an atmosphere driving the ocean process and the monopole mode to an ocean forcing the atmosphere process. The month-dependency and the statistical significance of the SVD modes are subjected to two Monte Carlo tests. The results are used to further explain the shifts in the SLP anomaly composites and to indirectly estimate the predominance of the proposed coupling processes during each winter month.

Volcanic effects on climate

Nature Climate Change, 2015

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