Understanding the snowmelt

Author:Renata Barradas Gutiérrez

Regions of the Canadian Arctic are experiencing unprecedented warming as a result of the greenhouse gases emitted by human activity. The western Arctic specifically has experienced significant increases in near surface ground temperatures over the past few decades, almost twice that of the global average temperature increase. This warming trend has resulted in significant changes to the regional ecosystems and the physical processes operating across these environments.

To better understand how the Arctic tundra will respond under further climate change scenarios, members of the Marsh Lab Trail Valley Creek (TVC) research group from Wilfrid Laurier University in Canada led by Dr. Philip Marsh travelled more than 4,000 kilometres to study the changing hydrology of Canada’s western Arctic using Leica Geosystems GNSS instruments. The research collects data on all components of the water cycle and aims to understand how further temperature increases will affect the local and regional freshwater systems by combining:

• detailed field observations
• remote sensing
• GNSS定位和建模。

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Survey time

一年一度的input of water stored as snow is the most important aspect to the hydrological cycle and the largest freshwater contributor to Arctic stream and lake systems. At the end of winter, between April to mid-May, Marsh Lab TVC researchers conduct snow surveys measuring the snow depths and water storage across multiple basins of study. The group of researchers accurately measures the annual snowfall accumulated over the winter months to quantify the amount of liquid water storage, measured as Snow Water Equivalent, and to calculate the amount of water available to the hydrological system once the snow melts.

To better understand the heterogeneous nature of the tundra snow cover, Marsh Lab TVC researchers use many recent technological advances, including:

• 无人驾驶汽车（UAV）
• 空中雪深度数据
• 自动雪深度记录探针
• 实验宇宙射线中子探针站。

研究人员目前使用两个Leica GS10 GNSS接收器和两个CS20现场控制器来收集各种研究项目的点类型数据。借助Leica Caintivate Field软件，团队收集和组织数据，而Leica Infinity调查软件则用于投影和过滤收集的现场点，以确保数据存储在正确的坐标系中。也使用了无人机后处理软件。

威尔弗里德·劳里尔大学（Wilfrid Laurier University）的研究助理布兰登·沃克（Branden Walker）表示：“我们的现场工作在很大程度上依赖于获得高精度的空间数据集，而我们的Leica Geosystems GNSS系统使所有这一切都成为可能。”“以前在其他研究站点使用Leica Geosystems仪器，结果出色，我们选择再次与他们一起参加该项目。”

研究人员组还使用GS10 GNSS接收器和CS20现场控制器来定期测量地面控制点，并对地形验证和变化多年冻土特征的检测进行调查。

沃克说：“我们正在进行的研究项目的大多数集中在获得高度精确和准确的GPS数据上。”“与其他数据集相比，Leica Geosystems GNSS系统已被证明可以提供强大而可靠的数据。”

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在上方和下方收集数据表格

测量较大区域雪的主要方法之一是通过实验使用无人机。为了验证，地理连接和纠正UAV中的GNSS数据，MARSH LAB TVC研究人员需要使用Leica GeoSystems GNSS系统测量地面上的实际雪和地面高度准确性水平。然后在Infinity调查软件和摄影测量软件中处理这些高度精确的地面控制点，以提高无人机映射点的准确性。

“The Leica Geosystems GNSS system we use allows us to create ground control points with a known position with sub-centimetre accuracy. This is very important for correcting our elevation products from the UAV, which may only differ from one flight to the next by a few centimetres,” said Walker. “This data allows us to quantify snow depth and water storage with previously unobtainable spatial and temporal resolutions. The data from our UAV is post processed and georeferenced using ground control points collected with our Leica RTK system to produce highly precise and accurate spatial datasets.

“我们的Leica Geosystems仪器是我们研究计划的骨干。我们的GNSS仪器提供的精度和准确性提供了使用UAV绘制小规模变化所需的空间数据，并帮助我们在设置和收集数据点时可以节省现场的时间。”

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Helping earth’s water mapping mission

MARSH LAB TVC研究人员使用Leica GeoSystems GNSS系统进行的研究也将是北美空气地表水和海洋地形（AIRSWOT）的主要地面验证，这是NASA的NASA北极硼脆弱性实验的组成部分（上图）。Airswot验证任务测量了航班期间尽可能多的湖泊上水的表面高度。Airswot是SWOT任务的一部分，该任务是从空间中绘制地球的水，以了解地球上有多少淡水并计算河流流量并监测沿海洋流。

NASA’s AirSWOT Phenomenology airborne radar flies across Northern Canada and Alaska measuring the Water Surface Elevation of tens of thousands of water bodies larger than 250 metres across. For the AirSWOT mission, the team has a small window to capture the measurements needed so they must have quick and reliable GNSS instruments that are capable of measuring from a long distance range from the base.

“The reliability of the rover to make quick and accurate measurements several kilometres from the base gives me confidence we will be able to validate NASA’s AirSWOT data successfully,” said Evan Wilcox, MSc Geography Candidate at Wilfrid Laurier University.

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Training field researchers

Marsh Lab TVC hosts research groups from North America and Europe who study Canada’s arctic regions. Wilfrid Laurier researchers regularly help train student researchers on how to use Leica Geosystems products.

“成为大学LED研究小组的一部分也导致了一个很高的学生转身，因此，Leica Geosystems产品的简单性和直观设计使培训下一轮的现场研究人员和学生变得更加容易 - 再次，节省了我们的小组时间和金钱bob综合app下载长期。”沃克补充说。

Harsh Arctic conditions can, furthermore, push the limits of most equipment. Leica Geosystems GNSS receivers and CS20 field controllers are designed to perform in the most extreme conditions.

“The nature of our field work tests all instruments to their absolute breaking point and maximum,” said Walker. “Our Leica GNSS systems have worked in a wide range of harsh arctic conditions, including temperatures of -20° Celsius.”

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Credible information on climate change

Backed up with the accuracy and precision of Leica Geosystems, the group of researchers are gaining a greater understanding on how the Arctic tundra systems have changed in response to increased air temperatures resulting from climate change. Accurate and reliable data is needed to better understand the complex relationship between snow depth, rain, lake levels, vegetation, permafrost and streamflow, and the physical processes at play to be able to predict future changes using mathematical models.

The data generated with this research is currently being used by a wide variety of research scientists and graduate students focussing on testing and validating new data collection techniques. The information obtained also contributes to a long standing research project that collects the historical dataset for the Arctic tundra. Understanding Arctic’s hydrological processes will provide credible information on how climate change is chaining lake levels, stream flows and snow cover, and how this affects the lives of Canadians.