The Experts below are selected from a list of 2334 Experts worldwide ranked by ideXlab platform
Donald L. Forbes - One of the best experts on this subject based on the ideXlab platform.
-
local spring warming drives earlier river Ice Breakup in a large arctic delta
Geophysical Research Letters, 2014Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier Ice Breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-Ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-Ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier Ice Breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier Ice Breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.
-
Local spring warming drives earlier river‐Ice Breakup in a large Arctic delta
Geophysical Research Letters, 2014Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier Ice Breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-Ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-Ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier Ice Breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier Ice Breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.
-
Timing, duration, and magnitude of peak annual water‐levels during Ice Breakup in the Mackenzie Delta and the role of river discharge
Water Resources Research, 2013Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:[2] North-flowing rivers of the pan-Arctic region have important effects on the Arctic Ocean, but their river-ocean interfaces, including some with vast deltas such as the Mackenzie, have complex hydrology and remain poorly understood. Analysis of 39 years (1973–2011) of water-levels and river discharge at the head of the Mackenzie Delta, 48 years (1964–2011) of water-levels in the mid-delta, and 28 years (1984–2011) of water-levels in the outer delta permitted evaluation of changes in the timing, duration, and magnitude of peak annual water-levels during river-Ice Breakup. The initiation date of freshet-discharge into the delta has not changed, but the duration from freshet initiation until peak water-levels in the central delta (i.e., duration of Ice clearance) has shortened from 35 to 27 days since 1964. The height of annual water-level peaks in the outer delta at Reindeer Channel may have declined by ∼0.4 m from 1984 to 2010, but complicating factors may be influencing this result. Winter-discharge has increased by ∼21% from 1973 to 2011, but this amount is too small to cause a trend in total Mackenzie discharge. Breakup-discharge (i.e., occurring during Ice clearance through the central delta) has not significantly changed. The lag time from freshet-discharge initiation into the delta until initial breakage of the river Ice-sheet has declined by 6.6 days from 1974 to 2007 and is sufficient to account for the shortened period of river-Ice clearance. Declining snow-pack depths during April suggest that river-Ice may be melting earlier and more rapidly.
-
timing duration and magnitude of peak annual water levels during Ice Breakup in the mackenzie delta and the role of river discharge
Water Resources Research, 2013Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:[2] North-flowing rivers of the pan-Arctic region have important effects on the Arctic Ocean, but their river-ocean interfaces, including some with vast deltas such as the Mackenzie, have complex hydrology and remain poorly understood. Analysis of 39 years (1973–2011) of water-levels and river discharge at the head of the Mackenzie Delta, 48 years (1964–2011) of water-levels in the mid-delta, and 28 years (1984–2011) of water-levels in the outer delta permitted evaluation of changes in the timing, duration, and magnitude of peak annual water-levels during river-Ice Breakup. The initiation date of freshet-discharge into the delta has not changed, but the duration from freshet initiation until peak water-levels in the central delta (i.e., duration of Ice clearance) has shortened from 35 to 27 days since 1964. The height of annual water-level peaks in the outer delta at Reindeer Channel may have declined by ∼0.4 m from 1984 to 2010, but complicating factors may be influencing this result. Winter-discharge has increased by ∼21% from 1973 to 2011, but this amount is too small to cause a trend in total Mackenzie discharge. Breakup-discharge (i.e., occurring during Ice clearance through the central delta) has not significantly changed. The lag time from freshet-discharge initiation into the delta until initial breakage of the river Ice-sheet has declined by 6.6 days from 1974 to 2007 and is sufficient to account for the shortened period of river-Ice clearance. Declining snow-pack depths during April suggest that river-Ice may be melting earlier and more rapidly.
John J Magnuson - One of the best experts on this subject based on the ideXlab platform.
-
Historical Trends, Drivers, and Future Projections of Ice Phenology in Small North Temperate Lakes in the Laurentian Great Lakes Region
Water, 2018Co-Authors: Bailey A. Hewitt, Huaxia Yao, John J Magnuson, Lianna Lopez, Katrina Gaibisels, Alyssa D. Murdoch, Scott N. Higgins, Andrew M. Paterson, James A. Rusak, Sapna SharmaAbstract:Lake Ice phenology (timing of Ice Breakup and freeze up) is a sensitive indicator of climate. We acquired time series of lake Ice Breakup and freeze up, local weather conditions, and large-scale climate oscillations from 1981–2015 for seven lakes in northern Wisconsin, USA, and two lakes in Ontario, Canada. Multiple linear regression models were developed to understand the drivers of lake Ice phenology. We used projected air temperature and precipitation from 126 climate change scenarios to forecast the day of year of Ice Breakup and freeze up in 2050 and 2070. Lake Ice melted 5 days earlier and froze 8 days later over the past 35 years. Warmer spring and winter air temperatures contributed to earlier Ice Breakup; whereas warmer November temperatures delayed lake freeze. Lake Ice Breakup is projected to be 13 days earlier on average by 2070, but could vary by 3 days later to 43 days earlier depending upon the degree of climatic warming by late century. Similarly, the timing of lake freeze up is projected to be delayed by 11 days on average by 2070, but could be 1 to 28 days later. Shortened seasonality of Ice cover by 24 days could increase risk of algal blooms, reduce habitat for coldwater fisheries, and jeopardize survival of northern communities reliant on Ice roads.
-
Oscillatory dynamics do not mask linear trends in the timing of Ice Breakup for Northern Hemisphere lakes from 1855 to 2004
Climatic Change, 2014Co-Authors: Sapna Sharma, John J MagnusonAbstract:Our analyses partition the relative influence of progressive climate change and large-scale climate drivers that can be associated with the Quasi-Biennial Oscillation (QBO), El Nino Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), solar sunspot cycle, and multi-decadal oscillations on lake Ice Breakup dates for thirteen Northern Hemisphere lakes. Oscillatory dynamics explain 26 % of the total variance in the time series compared with 15 % for linear trends, leaving 60 % unexplained and likely attributable, in part, to local weather. Significant oscillatory dynamics include frequencies in 2–3 year periods (9.4 % of the total variance), 3–6 year periods (8.2 %), 10–12 year periods (1.6 %) and various multidecadal periods (0.4–1.3 %). All 13 study lakes, although widely scattered in the Northern Hemisphere, had similar oscillatory dynamics and linear trends, emphasizing that global processes influence lake Ice Breakup locally. We illustrate that while quasi-periodic dynamics associated with large-scale climate drivers are important, they do not mask the clear evidence for progressive climate change.
-
influences of local weather large scale climatic drivers and the ca 11 year solar cycle on lake Ice Breakup dates 1905 2004
Climatic Change, 2013Co-Authors: Sapna Sharma, John J Magnuson, Gricelda Mendoza, Stephen R CarpenterAbstract:We investigate the temporal patterns in inter-annual variability in Ice Breakup dates for Lakes Mendota and Monona, Wisconsin, between 1905 and 2004. We analyze the contributions of long-term trends attributed to climate change, local weather, indIces of sunspots, and large-scale climatic drivers, such as the North Atlantic Oscillation (NAO) and El Niňo Southern Ocean Index (ENSO) on time series of lake-Ice Breakup. The relative importance of the aforementioned explanatory variables was assessed using linear regression and variation partitioning models accounting for cyclic temporal dynamics as represented by Moran Eigenvector Maps (MEM). Model results explain an average of 58 % of the variation in Ice Breakup dates. A combination of the long-term linear trends, rain and snowfall in the month prior to Breakup, air temperature in the winter prior to Breakup, cyclic dynamics associated with sunspot numbers, ENSO, and for Lake Mendota, NAO, all significantly influence the timing of Ice Breakup. Significant cycle lengths were 3.5, 9, 11, and 50 years. Despite their proximity, Lakes Mendota and Monona exhibit differences in how and which explanatory variables were incorporated into the models. Our results indicate that lake Ice dynamics are complex in both lakes and multiple interacting processes explain the residuals around the linear warming trends that characterize lake Ice records.
-
satellite monitoring of lake Ice Breakup on the laurentian shield 1980 1994
Photogrammetric Engineering and Remote Sensing, 1998Co-Authors: Randolph H Wynne, Thomas M Lillesand, Murray K Clayton, John J MagnusonAbstract:Lake Ice Breakup dates from 1980 to 1994 for 81 selected lakes and reservoirs in the U.S. upper Midwest and portions of Canada (60"N, 105"W to 40°N, 85OW) were determined employing analysis of 1,830 archival images from the visible band (0.54 to 0.70 pm) of the GOES-VISSR. The objectives were to investigate the utility of monitoring Ice phenology as a climate indicator and to assess regional trends in lake Ice Breakup dates. The dates of image~y represented the range available in the national archive at the time of this study. Comparison of satellite-derived Breakup dates with available ground reference data revealed a mean absolute difference of + 3.2 days and a mean difference of -0.4 days, well within the natural variability in lake Ice Breakup dates (u -- + 12 days) for a single lake over time. The predominant spatial trends of mean Ice Breakup dates can be attributed to latitude and snomfall [RZ = 93 percent). Analysis of the pooled data for all 81 lakes revealed a significant (p < 0.001) trend toward earlier Ice Breakup dates. A11 of the individual lakes exhibiting significant trends toward earlier Ice Breakup from 1980 to 1994 are located in southern Wisconsin.
-
evidence of recent warming and el nino related variations in Ice Breakup of wisconsin lakes
Limnology and Oceanography, 1996Co-Authors: Wendy L. Anderson, Dale M. Robertson, John J MagnusonAbstract:Ice Breakup dates from 1968 to 1988 were examined for 20 Wisconsin lakes to determine whether consistent interannual and long-term changes exist. Each Ice record had a trend toward earlier Breakup dates, as demonstrated by a negative slope with time, indicating a recent warming trend. The average change in Breakup dates was 0.82 d earlier per year for the lakes in southern Wisconsin, which was more extreme than that for the northern Wisconsin lakes (0.45 d yr -1 ). Interannual variation in Breakup dates was related to the warm phase of El Nino/Southern Oscillation (ENSO) episodes. El Nino events occurred five times during this period (1965, 1972, 1976, 1982, and 1986). Average Breakup dates were significantly earlier than average (5-14 d) during the mature phase of El Nino. This variability was affected by the location of the lake : El Nino-related variation was more evident for the southern lakes than the northern lakes. This difference was caused by the average date of Breakup for the southern lakes being in late March directly following the period when air temperatures were strongly related to El Nino events, whereas the average dates of Breakup of the northern lakes was in mid- to late April following a period when air temperatures were not significantly related to El Nifio events. Overall, the interannual and long-term patterns across Wisconsin were relatively consistent, indicating that recent warming and El Nino-related variation are regional climatic responses.
Lance F. W. Lesack - One of the best experts on this subject based on the ideXlab platform.
-
local spring warming drives earlier river Ice Breakup in a large arctic delta
Geophysical Research Letters, 2014Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier Ice Breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-Ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-Ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier Ice Breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier Ice Breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.
-
Local spring warming drives earlier river‐Ice Breakup in a large Arctic delta
Geophysical Research Letters, 2014Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier Ice Breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-Ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-Ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier Ice Breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier Ice Breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.
-
Timing, duration, and magnitude of peak annual water‐levels during Ice Breakup in the Mackenzie Delta and the role of river discharge
Water Resources Research, 2013Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:[2] North-flowing rivers of the pan-Arctic region have important effects on the Arctic Ocean, but their river-ocean interfaces, including some with vast deltas such as the Mackenzie, have complex hydrology and remain poorly understood. Analysis of 39 years (1973–2011) of water-levels and river discharge at the head of the Mackenzie Delta, 48 years (1964–2011) of water-levels in the mid-delta, and 28 years (1984–2011) of water-levels in the outer delta permitted evaluation of changes in the timing, duration, and magnitude of peak annual water-levels during river-Ice Breakup. The initiation date of freshet-discharge into the delta has not changed, but the duration from freshet initiation until peak water-levels in the central delta (i.e., duration of Ice clearance) has shortened from 35 to 27 days since 1964. The height of annual water-level peaks in the outer delta at Reindeer Channel may have declined by ∼0.4 m from 1984 to 2010, but complicating factors may be influencing this result. Winter-discharge has increased by ∼21% from 1973 to 2011, but this amount is too small to cause a trend in total Mackenzie discharge. Breakup-discharge (i.e., occurring during Ice clearance through the central delta) has not significantly changed. The lag time from freshet-discharge initiation into the delta until initial breakage of the river Ice-sheet has declined by 6.6 days from 1974 to 2007 and is sufficient to account for the shortened period of river-Ice clearance. Declining snow-pack depths during April suggest that river-Ice may be melting earlier and more rapidly.
-
timing duration and magnitude of peak annual water levels during Ice Breakup in the mackenzie delta and the role of river discharge
Water Resources Research, 2013Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:[2] North-flowing rivers of the pan-Arctic region have important effects on the Arctic Ocean, but their river-ocean interfaces, including some with vast deltas such as the Mackenzie, have complex hydrology and remain poorly understood. Analysis of 39 years (1973–2011) of water-levels and river discharge at the head of the Mackenzie Delta, 48 years (1964–2011) of water-levels in the mid-delta, and 28 years (1984–2011) of water-levels in the outer delta permitted evaluation of changes in the timing, duration, and magnitude of peak annual water-levels during river-Ice Breakup. The initiation date of freshet-discharge into the delta has not changed, but the duration from freshet initiation until peak water-levels in the central delta (i.e., duration of Ice clearance) has shortened from 35 to 27 days since 1964. The height of annual water-level peaks in the outer delta at Reindeer Channel may have declined by ∼0.4 m from 1984 to 2010, but complicating factors may be influencing this result. Winter-discharge has increased by ∼21% from 1973 to 2011, but this amount is too small to cause a trend in total Mackenzie discharge. Breakup-discharge (i.e., occurring during Ice clearance through the central delta) has not significantly changed. The lag time from freshet-discharge initiation into the delta until initial breakage of the river Ice-sheet has declined by 6.6 days from 1974 to 2007 and is sufficient to account for the shortened period of river-Ice clearance. Declining snow-pack depths during April suggest that river-Ice may be melting earlier and more rapidly.
-
Lengthening plus shortening of river‐to‐lake connection times in the Mackenzie River Delta respectively via two global change mechanisms along the arctic coast
Geophysical Research Letters, 2007Co-Authors: Lance F. W. Lesack, Philip MarshAbstract:[1] River deltas along the circumpolar arctic coast are lake-rich and poorly understood ecosystems, set in a region expected to change rapidly. Over the past 30+ years annual river-to-lake connection times in the Mackenzie Delta have lengthened (>30 days) in the lowest elevation lakes and may have shortened in the highest elevation lakes, respectively via sea level rise and declining effects of river-Ice Breakup. Lengthened connection times indicate summer low-water levels in the delta have increased by an amount (0.3 m) equivalent to three times local sea level rise (0.1 m) over the same period. Such an amplification effect of recent sea level rise has been completely unexpected and may be a result of enhanced storm surges in response to receding arctic sea Ice or coastal backwater effects on the river flow. Shortened connection times are consistent with other work showing a decline in river-Ice Breakup effects, an important control on annual peak water levels.
Huaxia Yao - One of the best experts on this subject based on the ideXlab platform.
-
Historical Trends, Drivers, and Future Projections of Ice Phenology in Small North Temperate Lakes in the Laurentian Great Lakes Region
Water, 2018Co-Authors: Bailey A. Hewitt, Huaxia Yao, John J Magnuson, Lianna Lopez, Katrina Gaibisels, Alyssa D. Murdoch, Scott N. Higgins, Andrew M. Paterson, James A. Rusak, Sapna SharmaAbstract:Lake Ice phenology (timing of Ice Breakup and freeze up) is a sensitive indicator of climate. We acquired time series of lake Ice Breakup and freeze up, local weather conditions, and large-scale climate oscillations from 1981–2015 for seven lakes in northern Wisconsin, USA, and two lakes in Ontario, Canada. Multiple linear regression models were developed to understand the drivers of lake Ice phenology. We used projected air temperature and precipitation from 126 climate change scenarios to forecast the day of year of Ice Breakup and freeze up in 2050 and 2070. Lake Ice melted 5 days earlier and froze 8 days later over the past 35 years. Warmer spring and winter air temperatures contributed to earlier Ice Breakup; whereas warmer November temperatures delayed lake freeze. Lake Ice Breakup is projected to be 13 days earlier on average by 2070, but could vary by 3 days later to 43 days earlier depending upon the degree of climatic warming by late century. Similarly, the timing of lake freeze up is projected to be delayed by 11 days on average by 2070, but could be 1 to 28 days later. Shortened seasonality of Ice cover by 24 days could increase risk of algal blooms, reduce habitat for coldwater fisheries, and jeopardize survival of northern communities reliant on Ice roads.
-
trends of Ice Breakup date in south central ontario
Journal of Geophysical Research, 2015Co-Authors: Huaxia YaoAbstract:Large-scale Ice phenology studies have revealed overall patterns of later freeze, earlier Breakup, and shorter duration of Ice in the Northern Hemisphere. However, there have been few studies regarding the trends, including their spatial patterns, in Ice phenology for individual waterbodies on a local or small regional scale, although the coherence of Ice phenology has been shown to decline rapidly in the first few hundred kilometers. In this study, we extracted trends, analyzed affecting factors, and investigated relevant spatial patterns for Ice Breakup date time series at 10 locations with record length ≥90 years in south-central Ontario, Canada. Wavelet methods, including the multiresolution analysis (MRA) method for nonlinear trend extraction and the wavelet coherence (WTC) method for identifying the teleconnections between large-scale climate modes and Ice Breakup date, are proved to be effective in Ice phenology analysis. Using MRA method, the overall trend of Ice Breakup date time series (1905–1991) varied from earlier Ice Breakup to later Ice Breakup, then to earlier Breakup again from south to north in south-central Ontario. Ice Breakup date is closely correlated with air temperature during certain winter/spring months, as well as the last day with snow on the ground and number of snow-on-ground days. The influences of solar activity and Pacific North American on Ice Breakup were comparatively uniform across south-central Ontario, while those of El Nino–Southern Oscillation, North Atlantic Oscillation, and Arctic Oscillation on Ice phenology changed with distance of 50–100 km in the north-south direction.
-
Trends of Ice Breakup date in south‐central Ontario
Journal of Geophysical Research: Atmospheres, 2015Co-Authors: Huaxia YaoAbstract:Large-scale Ice phenology studies have revealed overall patterns of later freeze, earlier Breakup, and shorter duration of Ice in the Northern Hemisphere. However, there have been few studies regarding the trends, including their spatial patterns, in Ice phenology for individual waterbodies on a local or small regional scale, although the coherence of Ice phenology has been shown to decline rapidly in the first few hundred kilometers. In this study, we extracted trends, analyzed affecting factors, and investigated relevant spatial patterns for Ice Breakup date time series at 10 locations with record length ≥90 years in south-central Ontario, Canada. Wavelet methods, including the multiresolution analysis (MRA) method for nonlinear trend extraction and the wavelet coherence (WTC) method for identifying the teleconnections between large-scale climate modes and Ice Breakup date, are proved to be effective in Ice phenology analysis. Using MRA method, the overall trend of Ice Breakup date time series (1905–1991) varied from earlier Ice Breakup to later Ice Breakup, then to earlier Breakup again from south to north in south-central Ontario. Ice Breakup date is closely correlated with air temperature during certain winter/spring months, as well as the last day with snow on the ground and number of snow-on-ground days. The influences of solar activity and Pacific North American on Ice Breakup were comparatively uniform across south-central Ontario, while those of El Nino–Southern Oscillation, North Atlantic Oscillation, and Arctic Oscillation on Ice phenology changed with distance of 50–100 km in the north-south direction.
Faye Hicks - One of the best experts on this subject based on the ideXlab platform.
-
local spring warming drives earlier river Ice Breakup in a large arctic delta
Geophysical Research Letters, 2014Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier Ice Breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-Ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-Ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier Ice Breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier Ice Breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.
-
Local spring warming drives earlier river‐Ice Breakup in a large Arctic delta
Geophysical Research Letters, 2014Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier Ice Breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-Ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-Ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier Ice Breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier Ice Breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.
-
Timing, duration, and magnitude of peak annual water‐levels during Ice Breakup in the Mackenzie Delta and the role of river discharge
Water Resources Research, 2013Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:[2] North-flowing rivers of the pan-Arctic region have important effects on the Arctic Ocean, but their river-ocean interfaces, including some with vast deltas such as the Mackenzie, have complex hydrology and remain poorly understood. Analysis of 39 years (1973–2011) of water-levels and river discharge at the head of the Mackenzie Delta, 48 years (1964–2011) of water-levels in the mid-delta, and 28 years (1984–2011) of water-levels in the outer delta permitted evaluation of changes in the timing, duration, and magnitude of peak annual water-levels during river-Ice Breakup. The initiation date of freshet-discharge into the delta has not changed, but the duration from freshet initiation until peak water-levels in the central delta (i.e., duration of Ice clearance) has shortened from 35 to 27 days since 1964. The height of annual water-level peaks in the outer delta at Reindeer Channel may have declined by ∼0.4 m from 1984 to 2010, but complicating factors may be influencing this result. Winter-discharge has increased by ∼21% from 1973 to 2011, but this amount is too small to cause a trend in total Mackenzie discharge. Breakup-discharge (i.e., occurring during Ice clearance through the central delta) has not significantly changed. The lag time from freshet-discharge initiation into the delta until initial breakage of the river Ice-sheet has declined by 6.6 days from 1974 to 2007 and is sufficient to account for the shortened period of river-Ice clearance. Declining snow-pack depths during April suggest that river-Ice may be melting earlier and more rapidly.
-
timing duration and magnitude of peak annual water levels during Ice Breakup in the mackenzie delta and the role of river discharge
Water Resources Research, 2013Co-Authors: Lance F. W. Lesack, Philip Marsh, Faye Hicks, Donald L. ForbesAbstract:[2] North-flowing rivers of the pan-Arctic region have important effects on the Arctic Ocean, but their river-ocean interfaces, including some with vast deltas such as the Mackenzie, have complex hydrology and remain poorly understood. Analysis of 39 years (1973–2011) of water-levels and river discharge at the head of the Mackenzie Delta, 48 years (1964–2011) of water-levels in the mid-delta, and 28 years (1984–2011) of water-levels in the outer delta permitted evaluation of changes in the timing, duration, and magnitude of peak annual water-levels during river-Ice Breakup. The initiation date of freshet-discharge into the delta has not changed, but the duration from freshet initiation until peak water-levels in the central delta (i.e., duration of Ice clearance) has shortened from 35 to 27 days since 1964. The height of annual water-level peaks in the outer delta at Reindeer Channel may have declined by ∼0.4 m from 1984 to 2010, but complicating factors may be influencing this result. Winter-discharge has increased by ∼21% from 1973 to 2011, but this amount is too small to cause a trend in total Mackenzie discharge. Breakup-discharge (i.e., occurring during Ice clearance through the central delta) has not significantly changed. The lag time from freshet-discharge initiation into the delta until initial breakage of the river Ice-sheet has declined by 6.6 days from 1974 to 2007 and is sufficient to account for the shortened period of river-Ice clearance. Declining snow-pack depths during April suggest that river-Ice may be melting earlier and more rapidly.
-
Neuro-fuzzy river Ice Breakup forecasting system
Cold Regions Science and Technology, 2006Co-Authors: C. Mahabir, Faye Hicks, Aminah Robinson FayekAbstract:Abstract Despite the serious threat posed to communities by Ice during spring river Ice Breakup, there are no reliable means to predict the severity of Breakup with a significant lead time. Building on previous data collection and regression analyses for the Athabasca River at Fort McMurray, this paper evaluates the application of soft computing through fuzzy logic and artificial neural networks for modeling the maximum water level during river Ice Breakup for both flood and non-flood event years. A prototype fuzzy logic model is presented, based on four input variables, each available with a lead time of several weeks prior to river Breakup. The performance of the model was evaluated for several designs including a neuro-fuzzy model created to reduce the subjectivity of expert knowledge for rule base definition. It was found that a simple fuzzy expert system, based exclusively on expert experience, could qualitatively distinguish years when flooding occurred but produced poor quantitative results. A neuro-fuzzy model was able to simulate water levels with an R 2 of 0.88, performing equally in comparison to a multiple linear regression model based on twIce as many input variables, some with much less lead time. The performance of this neuro-fuzzy model with relatively few input variables holds promise for modeling sites where the volume of available data is limited.