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  • 11
    Online Resource
    Online Resource
    Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4
    Copernicus GmbH ; 2015
    In:  Geoscientific Model Development Vol. 8, No. 10 ( 2015-10-06), p. 3119-3130
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 8, No. 10 ( 2015-10-06), p. 3119-3130
    Abstract: Abstract. Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO3.4 forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing give warmer surface waters, open larger polynyas causing more saline surface waters and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    DOI: 10.5194/gmd-8-3119-2015
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2015
    detail.hit.zdb_id: 2456725-5
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  • 12
    Online Resource
    Online Resource
    Gene expression and nitrogen loss in senescing root systems of red clover ( Trifolium pratense )
    Cambridge University Press (CUP) ; 2010
    In:  The Journal of Agricultural Science Vol. 148, No. 5 ( 2010-10), p. 579-591
    Details
    In: The Journal of Agricultural Science, Cambridge University Press (CUP), Vol. 148, No. 5 ( 2010-10), p. 579-591
    Abstract: Root system senescence and nitrogen (N) release from red clover ( Trifolium pratense L.) plants, grown under semi-sterile conditions and a controlled environment, were studied for 28 days following temporary or prolonged abiotic stress. Plants stressed temporarily, to simulate grazing, recovered with no additional N lost in leachate. In contrast, plants subjected to prolonged stress that simulated overwintering conditions and inhibited shoot re-growth survived stress lasting 7 days, but plant viability was reduced to 50% by 14 days and 0% at 21 days. There were no significant differences in root protein, catalase activity, root death index or total N loss in leachate over 21 days, but by 28 days total N loss in leachate increased to 214% above control levels, with a 433% increase in total oxidized N. This increase in N loss between 21 and 28 days indicated the start of cellular breakdown of the root system, coinciding with the failure of plants to recover. Key enzyme activities and protein concentrations in nodules decreased rapidly over 10 days' prolonged stress. cDNA–amplified fragment length polymorphism (AFLP) analysis identified contaminating bacterial and fungal genes, along with plant gene sequences with consistent or altered expression profiles. Four plant sequences, glyceraldehyde-3-phosphate dehydrogenase ( Tp-gapdh 1), nodule senescence reduced ( Tp-nsr 1), nodule senescence enhanced ( Tp-nse 1) and a cysteine protease gene ( Tp-cp 8) were differentially expressed throughout the plant: Tp-nsr 1 and Tp-nse 1 have potential as molecular markers for nodule senescence. Root and nodule death in agricultural legumes, such as red clover, are implicated in N release into watercourses and the wider environment. Differences in the ability of these plants to survive prolonged stress lasting 14 days, and the delayed release of root N into leachate until 28 days after the stress, highlight the potential for the development of new red clover varieties with different rates of root system senescence.
    Type of Medium: Online Resource
    ISSN: 0021-8596 , 1469-5146
    URL: Article
    DOI: 10.1017/S0021859610000420
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2010
    detail.hit.zdb_id: 1498349-7
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  • 13
    Online Resource
    Online Resource
    Ice-shelf – ocean interactions at Fimbul Ice Shelf, Antarctica from oxygen isotope ratio measurements
    Copernicus GmbH ; 2008
    In:  Ocean Science Vol. 4, No. 1 ( 2008-03-05), p. 89-98
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 4, No. 1 ( 2008-03-05), p. 89-98
    Abstract: Abstract. Melt water from the floating ice shelves at the margins of the southeastern Weddell Sea makes a significant contribution to the fresh water budget of the region. In February 2005 a multi-institution team conducted an oceanographic campaign at Fimbul Ice Shelf on the Greenwich Meridian as part of the Autosub Under Ice programme. This included a mission of the autonomous submarine Autosub 25 km into the cavity beneath Fimbul Ice Shelf, and a number of ship-based hydrographic sections on the continental shelf and adjacent to the ice shelf front. The measurements reveal two significant sources of glacial melt water at Fimbul Ice Shelf: the main cavity under the ice shelf and an ice tongue, Trolltunga, that protrudes from the main ice front and out over the continental slope into deep water. Glacial melt water is concentrated in a 200 m thick Ice Shelf Water (ISW) layer below the base of the ice shelf at 150–200 m, with a maximum glacial melt concentration of up to 1.16%. Some glacial melt is found throughout the water column, and much of this is from sources other than Fimbul Ice Shelf. However, at least 0.2% of the water in the ISW layer cannot be accounted for by other processes and must have been contributed by the ice shelf. Just downstream of Fimbul Ice Shelf we observe locally created ISW mixing out across the continental slope. The ISW formed here is much less dense than that formed in the southwest Weddell Sea, and will ultimately contribute a freshening (and reduction in δ18O) to the upper 100–150 m of the water column in the southeast Weddell Sea.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-4-89-2008
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2008
    detail.hit.zdb_id: 2183769-7
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  • 14
    Online Resource
    Online Resource
    Observations of oceanic mesoscale features and variability in the Canary Islands area from ERS-1 altimeter data, satellite infrared imagery and hydrographic measurements
    Informa UK Limited ; 2002
    In:  International Journal of Remote Sensing Vol. 23, No. 22 ( 2002-01), p. 4897-4916
    Details
    In: International Journal of Remote Sensing, Informa UK Limited, Vol. 23, No. 22 ( 2002-01), p. 4897-4916
    Type of Medium: Online Resource
    ISSN: 0143-1161 , 1366-5901
    URL: Article
    DOI: 10.1080/01431160110034681
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2002
    detail.hit.zdb_id: 1497529-4
    detail.hit.zdb_id: 754117-X
    SSG: 14
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  • 15
    Online Resource
    Online Resource
    Wind forcing of salinity anomalies in the Denmark Strait overflow
    Copernicus GmbH ; 2011
    In:  Ocean Science Vol. 7, No. 6 ( 2011-11-30), p. 821-834
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 7, No. 6 ( 2011-11-30), p. 821-834
    Abstract: Abstract. The overflow of dense water from the Nordic Seas to the North Atlantic through Denmark Strait is an important part of the global thermohaline circulation. The salinity of the overflow plume has been measured by an array of current meters across the continental slope off the coast of Angmagssalik, southeast Greenland since September 1998. During 2004 the salinity of the overflow plume changed dramatically; the entire width of the array (70 km) freshened between January 2004 and July 2004, with a significant negative salinity anomaly of about 0.06 in May. The event in May represents a fresh anomaly of over 3 standard deviations from the mean since recording began in 1998. The OCCAM 1/12° Ocean General Circulation Model not only reproduces the 2004 freshening event (r=0.96, p〈0.01), but also correlates well with salinity observations over a previous 6 year period (r=0.54, p〈0.01), despite the inevitable limitations of a z-coordinate model in representing the mixing processes at and downstream of the Denmark Strait sill. Consequently the physical processes causing the 2004 anomaly and prior variability in salinity are investigated using the model output. Our results reject the hypotheses that the anomaly is caused by processes occurring between the overflow sill and the moorings, or by an increase in upstream net freshwater input. Instead, we show that the 2004 salinity anomaly is caused by an increase in volume flux of low salinity water, with a potential density greater than 27.60 kg m−3, flowing towards the Denmark Strait sill in the East Greenland Current. This is caused by an increase in southward wind stress upstream of the sill at around 75° N 20° W four and a half months earlier, and an associated strengthening of the East Greenland Current.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-7-821-2011
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
    detail.hit.zdb_id: 2183769-7
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  • 16
    Online Resource
    Online Resource
    On the outflow of dense water from the Weddell and Ross Seas in OCCAM model
    Copernicus GmbH ; 2012
    In:  Ocean Science Vol. 8, No. 3 ( 2012-06-14), p. 369-388
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 8, No. 3 ( 2012-06-14), p. 369-388
    Abstract: Abstract. We describe the seasonal and interannual variability of volume transports in the Weddell and Ross Seas using the 1/12° 20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative volume transports were 28.5 ± 2.9 Sv (1 Sv ≡ 106 m3 s−1) and 13.4 ± 5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW) (defined by neutral density γn ≥ 28.27 kg m−3) from the Weddell and Ross Seas of 10.6 ± 3.1 Sv and 0.5 ± 0.7 Sv, respectively, agree with the range reported in historical observational studies. The export of Weddell Sea dense water in OCCAM is primarily determined by the strength of the Weddell Gyre. Variability in AABW export is predominantly at periods of ~1 yr and 2–4 yr.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-8-369-2012
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2012
    detail.hit.zdb_id: 2183769-7
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  • 17
    Online Resource
    Online Resource
    An Overview of the Synoptic Antarctic Shelf-Slope Interactions (SASSI) project for the International Polar Year
    Copernicus GmbH ; 2012
    In:  Ocean Science Vol. 8, No. 6 ( 2012-12-19), p. 1111-1116
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 8, No. 6 ( 2012-12-19), p. 1111-1116
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-8-1111-2012
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2012
    detail.hit.zdb_id: 2183769-7
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  • 18
    Online Resource
    Online Resource
    Direct observations of the Antarctic circumpolar current transport on the northern flank of the Kerguelen Plateau
    American Geophysical Union (AGU) ; 2013
    In:  Journal of Geophysical Research: Oceans Vol. 118, No. 3 ( 2013-03), p. 1333-1348
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 118, No. 3 ( 2013-03), p. 1333-1348
    Abstract: Complex meandering current system with STF/SAF to the north, PF to the south. Total eastward volume transport in the region is 174 {plus minus} 22 Sv. Presence of NIDW in the ACC on the northern flank of the Kerguelen Plateau.
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrc.v118.3
    DOI: 10.1002/jgrc.20067
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2013
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 19
    Online Resource
    Online Resource
    A novel method for measurement of the recto‐anal inhibitory reflex using anal acoustic reflectometry
    Wiley ; 2020
    In:  Colorectal Disease Vol. 22, No. 11 ( 2020-11), p. 1632-1641
    Details
    In: Colorectal Disease, Wiley, Vol. 22, No. 11 ( 2020-11), p. 1632-1641
    Abstract: The recto‐anal inhibitory reflex (RAIR) is currently measured using manometry catheters, which potentially distort the anal canal. Anal acoustic reflectometry (AAR) is considered to be a catheter‐free technique and primarily measures the function of the internal anal sphincter. We sought to determine if RAIR could be measured using AAR. Method Patients aged 18 and over attending the hospital for investigation of pelvic floor dysfunction were included. AAR parameters were obtained before (prerectal distension) and after (postrectal distension) inflation of a rectal balloon catheter with 100 ml of air. Minimum opening pressure (Op, cmH 2 O), opening elastance (Oe, cmH 2 O/mm 2 ), closing pressure (Cp, cmH 2 O), closing elastance (Ce, cmH 2 O/mm 2 ) and hysteresis (Hys, %) were recorded. The presence of RAIR was defined by a reduction of prerectal distension Op by 20% or more. Results Thirty‐two patients were included, 26 of whom were women. The mean age of patients was 57.5 years (SD 11.3 years). Nine patients had faecal incontinence, six patients had obstructive defaecation and 17 patients had both. RAIR was seen in 30/32 patients. The mean reduction in Op was 58.8% (range −59.18% to 100%). Three patients had 100% reduction. Comparison of pre‐ and post‐RAIR parameters showed a significant difference in Op (34.44 vs 15.41, P   〈  0.0001), Oe (1.39 vs 1.1, P  = 0.004), Cp (20.06 vs 8.00, P   〈  0.0001) and Ce (1.31 vs 1.13, P   〈  0.0001) but not Hys (39.71 vs 39.90, P  = 0.88). Conclusion We describe a novel method for the measurement of RAIR. Rectal distension appears to alter resting pressure and the resistance of the anal canal to opening and closing, with complete inhibition of the sphincter complex in three patients.
    Type of Medium: Online Resource
    ISSN: 1462-8910 , 1463-1318
    URL: Issue
    URL: Article
    DOI: 10.1111/codi.v22.11
    DOI: 10.1111/codi.15110
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2004820-8
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  • 20
    Online Resource
    Online Resource
    Placement of a fine‐bore rectal balloon catheter in the anal canal does not affect anal sphincter pressures: improving our understanding of physiological function with anal acoustic reflectometry
    Wiley ; 2020
    In:  Colorectal Disease Vol. 22, No. 11 ( 2020-11), p. 1626-1631
    Details
    In: Colorectal Disease, Wiley, Vol. 22, No. 11 ( 2020-11), p. 1626-1631
    Abstract: The recto‐anal inhibitory reflex (RAIR) is currently measured using anorectal manometry catheters, which may distort the anal canal. Anal acoustic reflectometry (AAR) is considered a catheter‐free technique for evaluating the physiological function of the anal canal; however, it has yet to be used to elicit the RAIR. For the RAIR to be measured with AAR, the effect of placing an additional rectal balloon catheter on the measured AAR parameters needs to be investigated: that is the aim of this work. Method Patients aged over 18 years attending hospital for the investigation of pelvic floor disorders were included. AAR parameters were obtained before and after a rectal balloon catheter was placed alongside the AAR catheter. The following parameters were measured: opening pressure (Op, cmH 2 O), opening elastance (Oe, cmH 2 O/mm 2 ), closing pressure (Cp, cmH 2 O), closing elastance (Ce, cmH 2 O/mm 2 ), hysteresis (Hys, %), squeeze opening pressure (SqOp, cmH 2 O) and squeeze opening elastance (SqOe, cmH 2 O/mm 2 ). Results Thirty‐five patients were included in the analysis, of whom 28 were women. The median age was 58 years. Comparison of median AAR parameters before and after catheter placement showed no significant difference: Op (36.36 vs 33.42, P  = 0.09), Oe (1.27 vs 1.39, P  = 0.19), Cp (18.62 vs 19.73, P  = 0.13), Ce (1.2 vs 1.28, P  = 0.33), Hys (41.08 vs 40.11, P  = 0.17), SqOp (81.85 vs 81.65, P  = 0.93) and SqOe (1.44 vs 1.49, P  = 0.55). Discussion Placement of a rectal balloon catheter alongside the AAR catheter has no significant effect on the measured AAR parameters. The results of this study add to the fundamental basic science and understanding of the physiological function of the anal canal.
    Type of Medium: Online Resource
    ISSN: 1462-8910 , 1463-1318
    URL: Issue
    URL: Article
    DOI: 10.1111/codi.v22.11
    DOI: 10.1111/codi.15300
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2004820-8
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