ORCID Profile
0000-0002-4810-9246
Current Organisation
University of British Columbia
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Publisher: Wiley
Date: 05-2007
Publisher: Copernicus GmbH
Date: 12-09-2017
Abstract: Abstract. Changes in the depth of the freshwater–seawater interface in epishelf lakes have been used to infer long-term changes in the minimum thickness of ice shelves however, little is known about the dynamics of epishelf lakes and what other factors may influence their depth. Continuous observations collected between 2011 and 2014 in the Milne Fiord epishelf lake, in the Canadian Arctic, showed that the depth of the halocline varied seasonally by up to 3.3 m, which was comparable to interannual variability. The seasonal depth variation was controlled by the magnitude of surface meltwater inflow and the hydraulics of the inferred outflow pathway, a narrow basal channel in the Milne Ice Shelf. When seasonal variation and an episodic mixing of the halocline were accounted for, long-term records of depth indicated there was no significant change in thickness of ice along the basal channel from 1983 to 2004, followed by a period of steady thinning at 0.50 m a−1 between 2004 and 2011. Rapid thinning at 1.15 m a−1 then occurred from 2011 to 2014, corresponding to a period of warming regional air temperatures. Continued warming is expected to lead to the breakup of the ice shelf and the imminent loss of the last known epishelf lake in the Arctic.
Publisher: Wiley
Date: 29-03-2021
Publisher: American Geophysical Union (AGU)
Date: 08-2020
DOI: 10.1029/2019WR025790
Abstract: The catastrophic August 2014 Mount Polley tailings spill, the second largest ever documented, sent ~18 Mm 3 of waste plunging to the bottom of the m deep West Basin of Quesnel Lake, British Columbia, a critical West Coast salmon habitat. To understand the impact of the spill on the lake, including the fate of suspended solids, we examine changes in physical water properties over 11 years (2006–2017) using water column profiles, moored timeseries, and satellite imagery. Contaminated waters were initially largely confined to the hypolimnion however, during autumn 2014 turnover, turbid waters were mixed to the surface, resulting in the clear blue lake turning bright green. Twelve months after the spill, the lake's temperature, conductivity, and turbidity temporarily returned to pre‐spill conditions however, initiation of mine effluent discharge in late 2015 was associated with a subsequent 15 μS cm −1 conductivity increase above historic values. Importantly, a post‐spill 1–2.5 formazin turbidity unit hypolimnetic turbidity increase was observed during spring and fall turnovers of 2015–2017, which appeared to be due to resuspension of a thin layer of unconsolidated spill‐related material from the lake bed driven by large internal seiche motions. This process implies spill contaminants may be seasonally mobilized into the water column, with potentially detrimental impacts on aquatic ecology. Our findings underscore that basin‐scale physical processes, including seasonal turnover and internal seiches, must be accounted for, even in deep lakes, to understand the long‐term impact of the ever increasing number of tailings spills into aquatic ecosystems.
Publisher: American Geophysical Union (AGU)
Date: 28-06-2021
DOI: 10.1029/2020JC016975
Abstract: Understanding the impact of the break‐up of northern Ellesmere Island ice shelves on fjord dynamics is limited by a lack of ocean observations prior to ice loss. Based on profiling and mooring data collected between 2011 and 2019, we describe the oceanography of Milne Fiord prior to the 2020 breakup of the Milne Ice Shelf, including, sources of ambient water, under‐ice hydrography, glacial modification, and seasonality. Ambient waters originate in the Canada Basin but are modified by interaction with the 100 m thick ice shelf at the fjord entrance, and extensive glacier tongue at the head. Properties within the 436 m deep fjord are depth‐dependent, with freshwater surface runoff and subglacial discharge accumulating in the upper 50 m of the fjord each summer behind the ice shelf. Freshwater export is restricted to a basal channel in the ice shelf, resulting in the fjord being more stratified and warmer than waters offshore year‐round. Below the ice shelf and above a 260 m deep sill unrestricted exchange allows warm Atlantic Water to penetrate to the 150 m deep glacier grounding line where submarine melting occurs. Basal meltwater spreads down‐fjord close to its depth of origin due to the strong stratification. Interannual warming of fjord deepwater is likely driven by shoaling of the Arctic Ocean thermocline and spillover at the sill, highlighting the link between fjord properties and regional oceanography. Further breakup of the ice shelf is predicted to substantially alter fjord dynamics, with consequences for ocean forcing of the Milne Glacier.
Publisher: Wiley
Date: 09-11-2009
DOI: 10.1111/J.1472-4669.2009.00215.X
Abstract: This study determined the natural abundance isotopic compositions ((13)C, (14)C) of the primary carbon pools and microbial communities associated with modern freshwater microbialites located in Pavilion Lake, British Columbia, Canada. The Delta(14)C of dissolved inorganic carbon (DIC) was constant throughout the water column and consistent with a primarily atmospheric source. Observed depletions in DIC (14)C values compared with atmospheric CO(2) indicated effects due either to DIC residence time and/or inputs of (14)C-depleted groundwater. Mass balance comparisons of local and regional groundwater indicate that groundwater DIC could contribute a maximum of 9-13% of the DIC. (14)C analysis of microbial phospholipid fatty acids from microbialite communities had Delta(14)C values comparable with lake water DIC, demonstrating that lake water DIC was their primary carbon source. Microbialite carbonate was also primarily derived from DIC. However, some depletion in microbialite carbonate (14)C relative to lake water DIC occurred, due either to residence time or mixing with a (14)C-depleted carbon source. A detrital branch covered with microbialite growth was used to estimate a microbialite growth rate of 0.05 mm year(-1) for the past 1000 years, faster than previous estimates for this system. These results demonstrate that the microbialites are actively growing and that the primary carbon source for both microbial communities and recent carbonate is DIC originating from the atmosphere. While these data cannot conclusively differentiate between abiotic and biotic formation mechanisms, the evidence for minor inputs of groundwater-derived DIC is consistent with the previously hypothesized biological origin of the Pavilion Lake microbialites.
Publisher: IEEE
Date: 10-2008
Publisher: Wiley
Date: 10-1994
Publisher: Elsevier BV
Date: 12-2013
Publisher: Elsevier BV
Date: 09-2014
Publisher: American Geophysical Union (AGU)
Date: 30-08-2021
DOI: 10.1029/2021JC017324
Abstract: Milne Ice Shelf is located at the mouth of Milne Fiord (82.6°N, 81.0°W), on Ellesmere Island, Nunavut. This floating ice feature is attached to both sides of the fjord. During the melt season, the ice shelf acts as a floating barrier preventing surface runoff in Milne Fiord from flowing freely to the ocean. This results in a permanent layer of freshwater that floats on top of the seawater of the fjord, commonly known as an epishelf lake. Few studies address the physical characteristics of epishelf lakes. Here, winter data from a mooring installed in Milne Fiord epishelf lake during 2011–2019 is analyzed in the framework of a one‐dimensional model in order to study mixing in the upper water column and infer the characteristics of a basal channel in the ice shelf. The results show that vertical mixing rates are higher in the epishelf lake than in the seawater below. Estimation of the Richardson number using a geostrophic balance approach reveals that enhanced mixing in the epishelf lake is associated with horizontal temperature gradients. In contrast to most studies on basal channels in Greenland and Antarctica, the results presented here show the basal channel of Milne Ice Shelf is apparently not evolving (melting) rapidly.
Publisher: American Geophysical Union (AGU)
Date: 05-2022
DOI: 10.1029/2021WR030574
Abstract: On 4 August 2014, a tailings dam failure at Mount Polley Mine in central British Columbia led to the largest short‐term release of mine waste into a lake ever recorded. Once released by the breach, slurry entered the smaller of Quesnel Lake’s two basins, called the West Basin, from which the lake drains northwest into the Quesnel River. An estimated 38,000 ± 11,000 tonnes of fine solids remained suspended in the West Basin on 10 September 2014, 37 days postspill. This decreased to within background levels ( tonnes) by June 2015, by which time ∼4,000 tonnes of sediment had flowed from the West Basin into the Quesnel River, and ∼31,000 tonnes had been transported east into the main basin, the direction opposed to the mean hydraulic gradient. Here, we evaluate sediment transport in Quesnel Lake following the Mount Polley tailings dam spill. We apply conservation of mass in two ways: using data collected between 12 August 2014 and 15 October 2020 to estimate suspended sediment mass and mass flows into and out of the West Basin and using one‐ and two‐basin completely mixed models. Suspended sediment concentrations were highly elevated through the first three seasons postspill, then fluctuated within a gradually decreasing, seasonal cycle. The observed mass trend and an analytical mass balance model of a simplified, two‐basin system suggest that suspended sediment mass will fall to below the median prespill mass by 7 ± 5 years postspill.
Publisher: Wiley
Date: 09-2008
Publisher: Elsevier BV
Date: 02-2014
Publisher: IEEE
Date: 2008
Publisher: Wiley
Date: 2012
Publisher: Springer Science and Business Media LLC
Date: 29-08-2005
Publisher: Wiley
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 23-11-2012
Publisher: Wiley
Date: 17-12-2014
DOI: 10.1111/GBI.12121
Abstract: Quantitative tools for deciphering the environment of microbialite formation are relatively limited. For ex le, the oxygen isotope carbonate-water geothermometer requires assumptions about the isotopic composition of the water of formation. We explored the utility of using 'clumped' isotope thermometry as a tool to study the temperatures of microbialite formation. We studied microbialites recovered from water depths of 10-55 m in Pavilion Lake, and 10-25 m in Kelly Lake, spanning the thermocline in both lakes. We determined the temperature of carbonate growth and the (18)O/(16)O ratio of the waters that microbialites grew in. Results were then compared to current limnological data from the lakes to reconstruct the history of microbialite formation. Modern microbialites collected at shallow depths (11.7 m) in both lakes yield clumped isotope-based temperatures of formation that are within error of summer water temperatures, suggesting that clumped isotope analyses may be used to reconstruct past climates and to probe the environments in which microbialites formed. The deepest microbialites (21.7-55 m) were recovered from below the present-day thermoclines in both lakes and yield radioisotope ages indicating they primarily formed earlier in the Holocene. During this time, pollen data and our reconstructed water (18)O/(16)O ratios indicate a period of aridity, with lower lake levels. At present, there is a close association between both photosynthetic and heterotrophic communities, and carbonate precipitation/microbialite formation, with biosignatures of photosynthetic influences on carbonate detected in microbialites from the photic zone and above the thermocline (i.e., depths of generally <20 m). Given the deeper microbialites are receiving <1% of photosynthetically active radiation (PAR), it is likely these microbialites primarily formed when lower lake levels resulted in microbialites being located higher in the photic zone, in warm surface waters.
Publisher: Elsevier BV
Date: 05-2010
Publisher: Wiley
Date: 05-2003
Publisher: Elsevier BV
Date: 09-2012
Publisher: Elsevier BV
Date: 03-2010
Publisher: MDPI AG
Date: 27-12-2012
DOI: 10.3390/LIFE3010021
Abstract: The presence of microbialite structures in a freshwater, dimictic mid-latitudelake and their establishment after the last ice age about 10,000 years ago is puzzling.Freshwater calcite microbialites at Pavilion Lake, British Columbia, Canada, consist of acomplex community of microorganisms that collectively form large, ordered structuredaggregates. This distinctive assemblage of freshwater calcite microbialites was studied through standard microbial methods, morphological observations, phospholipid fatty acid(PLFA) analysis, DNA sequencing and the identification of quorum sensing molecules.Our results suggest that the microbialites may represent a transitional form from theexclusively prokaryotic colonial precursors of stromatolites to the multicellular organismicaggregates that give rise to coral reefs.
Publisher: Elsevier BV
Date: 2006
Publisher: Springer Science and Business Media LLC
Date: 21-07-2012
Publisher: Elsevier BV
Date: 15-04-2008
Publisher: Elsevier BV
Date: 06-2010
Publisher: IEEE
Date: 09-2007
Publisher: Springer Science and Business Media LLC
Date: 10-2000
DOI: 10.1038/35036579
Abstract: Microbialites are organosedimentary structures that can be constructed by a variety of metabolically distinct taxa. Consequently, microbialite structures abound in the fossil record, although the exact nature of the biogeochemical processes that produced them is often unknown. One such class of ancient calcareous structures, Epiphyton and Girvanella, appear in great abundance during the Early Cambrian. Together with Archeocyathids, stromatolites and thrombolites, they formed major Cambrian reef belts. To a large extent, Middle to Late Cambrian reefs are similar to Precambrian reefs, with the exception that the latter, including terminal Proterozoic reefs, do not contain Epiphyton or Girvanella. Here we report the discovery in Pavilion Lake, British Columbia, Canada, of a distinctive assemblage of freshwater calcite microbialites, some of which display microstructures similar to the fabrics displayed by Epiphyton and Girvanella. The morphologies of the modern microbialites vary with depth, and dendritic microstructures of the deep water (> 30 m) mounds indicate that they may be modern analogues for the ancient calcareous structures. These microbialites thus provide an opportunity to study the biogeochemical interactions that produce fabrics similar to those of some enigmatic Early Cambrian reef structures.
Publisher: Springer Science and Business Media LLC
Date: 03-09-2012
Publisher: Elsevier BV
Date: 03-2008
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2003
Publisher: Wiley
Date: 14-06-2013
Publisher: Schweizerbart
Date: 2009
Publisher: Wiley
Date: 1997
No related grants have been discovered for Bernard Edmond Laval.