NWT RESEARCH DATABASE

Tags: physical sciences, limnology, ocean physics, delta lakes, hydrological evolution

Objective(s): The goals of this research are to examine: 1) measurements of water depths and lake depths for selected area of the Mackenzie Delta; 2) changes in lake flooding and historical lake boundaries in the Mackenzie Delta.

Project Description: The goals of this research are to examine: 1) measurements of water depths and lake depths for selected area of the Mackenzie Delta; 2) changes in lake flooding and historical lake boundaries in the Mackenzie Delta. Specific activities for this field season include the following: (1) Improved information on the detailed topography of the Mackenzie Delta floodplain and how delta water levels and nutrients in the waters are affected by the topography represents new work being launched this year. This information is needed to address an important knowledge gap and complement an International Polar Year investigation on channel network water levels in the delta (IPY-SCARF), via developing ability to model how changing low- and high-water levels will quantitatively affect the area and water volume of off-channel aquatic habitat in the Mackenzie Delta, including the Kendall Island Bird Sanctuary of the outer delta. Recent prior work shows that over the past 30+ years, summer low-water levels in the delta may have increased by an amount (0.3 m) equivalent to three times local sea level rise (0.1 m) over the same period. Such amplification of recent sea level rise has been 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. Other work suggests a recent decline in river-ice breakup effects in the delta that historically have been an important control on annual peak water levels. During summer 2009 this study will be restricted to preliminary work on (a) improving estimates of delta lake water and ice levels plus lake volumes via making under-ice water-depth measurements in representative lakes selected for our modeling work; and (b) improving estimates of under-ice nutrient content in delta lakes via making nutrient measurements in the lakes selected for our water level and volume measurements. This research will be based from the Aurora Research Institute and most of this work will be completed during May as follows. (i) GPS survey will be done to measure ice and water levels at 12 lakes with each of 4 areas of the delta (see attached maps of delta-lakes1, delta-lakes3, and delta-lakes4). (ii) Under-ice water samples will be collected at the times of the GPS lake surveys and brought back to the lab at the Aurora Research Institute for analysis of phosphorus, nitrogen, carbon, and various other trace elements. (iii) For comparison with the lake water samples, water samples will also be collected from under the river-ice at the Water Survey Canada gauging station on the Mackenzie River upstream from Tsiigehtchic. (2) Assessing changes in lake flooding and historical lake boundaries in the Mackenzie Delta. Important information needed to assess how long-term changes in water levels will affect the delta is the ability to estimate potential effects in years where water levels are higher, or lower, than what has been observed in the limited 30 year record, and assessing whether observations from 50 year ago are still valid. Developing such capability requires expanding the information presently available on areal extent and depth of annual flooding during breakup of the delta. Prior information on lake flooding regimes, plus recent map-based census of delta lakes, are based on topographic maps derived from 1950's aerial photography. During summer 2009, this study will assess the hypothesis that changes in lake abundances and land-water boundaries have changed minimally since the 1950's aerial photography was taken. GIS analysis will compare 2008 aerial photos and satellite imagery against the 1950's maps of the delta. Field work will involve investigating specific areas of the delta where changes are evident (e.g. lake disappearance or appearance of new lakes). The field work will be based from the Aurora Research Institute and will consist of accessing a number of lakes via helicopter during late July or early August to make GPS survey measurements of lake-shore shapes, measure water depths, and take aerial photography of specific lakes of interest. Field work will be based on four areas where the researchers have worked extensively in the past. Research is posted on the Mackenzie Delta research at http://www.sfu.ca/limnology. This highlights the research and student opportunities for training in arctic-based research. The fieldwork for this study will be conducted at 4 clusters of lake in the Delta Region a) Opposite to the Inuvik Town Site; 2) North of Inuvik (East Channel); 3) North-East Point Separation; 4) Close to Williams Island from May 8 to August 28, 2009. Please contact the research for specific research locations.