Alia Khan | Western Washington University (original) (raw)
Papers by Alia Khan
Zenodo (CERN European Organization for Nuclear Research), Jan 23, 2023
Geological Society of America Abstracts with Programs
Geological Society of America Abstracts with Programs
Geosciences, 2019
Quantitative estimates of future Antarctic climate change are derived from numerical global clima... more Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds t...
Communications Earth & Environment
Snow algae are ubiquitous in the Pacific Northwest cryosphere in the summer where snowmelt is an ... more Snow algae are ubiquitous in the Pacific Northwest cryosphere in the summer where snowmelt is an important contribution to regional watersheds. However, less attention has been given to biological impurities as drivers of snowmelt compared to inorganic light-absorbing particles. Here we map snow algae near Mt. Baker with a multispectral camera on an uncrewed aerial vehicle using (1) principal components and (2) spectral indexing. The two approaches are tested under differing bloom states and verified with coincident algal pigment and cell count data. During high bloom intensity we found an average instantaneous radiative forcing of 237 W m−2 with a maximum of 360 W m−2. This translated to 1,508 ± 536 m3 of melted snow water equivalent in the 0.1 km2 basin. These results demonstrate snow algae contribute to snowmelt at mid-latitudes and the potential for uncrewed autonomous vehicles to map snow algae over expansive areas of the cryosphere.
Frontiers in Environmental Science, 2021
Previous studies have shown that algal-derived dissolved organic matter (DOM) has a strong influe... more Previous studies have shown that algal-derived dissolved organic matter (DOM) has a strong influence on the formation of disinfection byproducts (DBPs) during the treatment of drinking water. In the summer of 2010, we evaluated the role of nitrogen and phosphorus loading and phytoplankton abundance as drivers of the concentrations and quality of DOM and the associated DBP formation in 30 reservoirs in the mountains and plains of the State of Colorado. Optical properties such as Specific Ultraviolet Absorbance at 254 nm (SUVA254) and fluorescence spectroscopy were used to characterize DOM quality. Nutrient concentrations such as total nitrogen were also assessed and were associated with high concentrations of chlorophyll a (Chl-a). In turn, high total organic carbon (TOC) concentrations were associated with high concentrations of Chl-a, and the DOM in these reservoirs had a fluorescence signature indicative of contributions from phytoplankton growth. The reservoirs with TOC concentra...
Journal of Geophysical Research: Atmospheres, 2017
Frontiers in Earth Science
Earth and Planetary Science Letters
Remote Sensing of Environment
<p&amp... more <p>Assessing the albedo response due to light-absorbing impurities (LAI) in coastal snowpacks has become of great interest in the light of the ‘Antarctic greening’. Reductions in the albedo (triggered by a change in air temperature or by the LAI deposition) can also enhance feedback mechanisms; as the albedo drops, the fraction of absorbed solar energy increases, which leads to additional albedo drops.</p><p>Here we assess the presence of Black Carbon (BC) and LAI in coastal snowpacks in the Antarctic Peninsula. The BC-equivalent contentwas assessed by applying the meltwater filtration (MF) technique to snow samples taken at 7 locations in theAntarctic Peninsula, from latitude 62<sup>o</sup>S to latitude 67<sup>o</sup>S. BC-equivalentconcentrations exhibited significant geographical differences,but were found to be generally lower than 5 ng/g (in the range of those reported for the Arctic Ocean and Greenland). Moreover, the Angstrom coefficients were found to be particularly high at the northern tip of the Antarctic Peninsula,likely due to the snow algae presence. After the onset of melt, red snow algae bloom, significantly affecting the surface albedo, as shown by our measurements.</p>
Frontiers in Earth Science
Eos
The #GreatAntarcticClimateHack; La Jolla, California, 9–12 October 2017
The Cryosphere Discussions
Journal of Geophysical Research: Atmospheres
Journal of Geophysical Research: Earth Surface
Regional Environmental Change
Geophysical Research Letters
Marine genomics, Jan 29, 2017
The biodiversity, ecosystem services and climate variability of the Antarctic continent and the S... more The biodiversity, ecosystem services and climate variability of the Antarctic continent and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds - Ecosystem Resilience and Adaptation of the Scientific Committee on Antarctic Research, which focussed on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas and first steps in their implementation were clustered into eight themes. These ranged from scale problems, through risk maps, and organism/ecosystem responses to multiple environmental changes and evolutionary processes. Scaling models and data across differe...
Zenodo (CERN European Organization for Nuclear Research), Jan 23, 2023
Geological Society of America Abstracts with Programs
Geological Society of America Abstracts with Programs
Geosciences, 2019
Quantitative estimates of future Antarctic climate change are derived from numerical global clima... more Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds t...
Communications Earth & Environment
Snow algae are ubiquitous in the Pacific Northwest cryosphere in the summer where snowmelt is an ... more Snow algae are ubiquitous in the Pacific Northwest cryosphere in the summer where snowmelt is an important contribution to regional watersheds. However, less attention has been given to biological impurities as drivers of snowmelt compared to inorganic light-absorbing particles. Here we map snow algae near Mt. Baker with a multispectral camera on an uncrewed aerial vehicle using (1) principal components and (2) spectral indexing. The two approaches are tested under differing bloom states and verified with coincident algal pigment and cell count data. During high bloom intensity we found an average instantaneous radiative forcing of 237 W m−2 with a maximum of 360 W m−2. This translated to 1,508 ± 536 m3 of melted snow water equivalent in the 0.1 km2 basin. These results demonstrate snow algae contribute to snowmelt at mid-latitudes and the potential for uncrewed autonomous vehicles to map snow algae over expansive areas of the cryosphere.
Frontiers in Environmental Science, 2021
Previous studies have shown that algal-derived dissolved organic matter (DOM) has a strong influe... more Previous studies have shown that algal-derived dissolved organic matter (DOM) has a strong influence on the formation of disinfection byproducts (DBPs) during the treatment of drinking water. In the summer of 2010, we evaluated the role of nitrogen and phosphorus loading and phytoplankton abundance as drivers of the concentrations and quality of DOM and the associated DBP formation in 30 reservoirs in the mountains and plains of the State of Colorado. Optical properties such as Specific Ultraviolet Absorbance at 254 nm (SUVA254) and fluorescence spectroscopy were used to characterize DOM quality. Nutrient concentrations such as total nitrogen were also assessed and were associated with high concentrations of chlorophyll a (Chl-a). In turn, high total organic carbon (TOC) concentrations were associated with high concentrations of Chl-a, and the DOM in these reservoirs had a fluorescence signature indicative of contributions from phytoplankton growth. The reservoirs with TOC concentra...
Journal of Geophysical Research: Atmospheres, 2017
Frontiers in Earth Science
Earth and Planetary Science Letters
Remote Sensing of Environment
<p&amp... more <p>Assessing the albedo response due to light-absorbing impurities (LAI) in coastal snowpacks has become of great interest in the light of the ‘Antarctic greening’. Reductions in the albedo (triggered by a change in air temperature or by the LAI deposition) can also enhance feedback mechanisms; as the albedo drops, the fraction of absorbed solar energy increases, which leads to additional albedo drops.</p><p>Here we assess the presence of Black Carbon (BC) and LAI in coastal snowpacks in the Antarctic Peninsula. The BC-equivalent contentwas assessed by applying the meltwater filtration (MF) technique to snow samples taken at 7 locations in theAntarctic Peninsula, from latitude 62<sup>o</sup>S to latitude 67<sup>o</sup>S. BC-equivalentconcentrations exhibited significant geographical differences,but were found to be generally lower than 5 ng/g (in the range of those reported for the Arctic Ocean and Greenland). Moreover, the Angstrom coefficients were found to be particularly high at the northern tip of the Antarctic Peninsula,likely due to the snow algae presence. After the onset of melt, red snow algae bloom, significantly affecting the surface albedo, as shown by our measurements.</p>
Frontiers in Earth Science
Eos
The #GreatAntarcticClimateHack; La Jolla, California, 9–12 October 2017
The Cryosphere Discussions
Journal of Geophysical Research: Atmospheres
Journal of Geophysical Research: Earth Surface
Regional Environmental Change
Geophysical Research Letters
Marine genomics, Jan 29, 2017
The biodiversity, ecosystem services and climate variability of the Antarctic continent and the S... more The biodiversity, ecosystem services and climate variability of the Antarctic continent and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds - Ecosystem Resilience and Adaptation of the Scientific Committee on Antarctic Research, which focussed on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas and first steps in their implementation were clustered into eight themes. These ranged from scale problems, through risk maps, and organism/ecosystem responses to multiple environmental changes and evolutionary processes. Scaling models and data across differe...