U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3040

March 2011

The Yukon River Basin Active Layer Network: A Cooperative 

Project between the Yukon River Inter-Tribal Watershed Council 

and the U.S. Geological Survey

Printed on recycled paper

Introduction

The Active Layer Network (ALN) was launched in 2009 

as a cooperative project between the Yukon River Inter-Tribal 

Watershed Council (YRITWC) and the U.S. Geological 

Survey (USGS) (https://sites.google.com/a/yritwc.org/

active-layer-network/?pli=1).* The active layer is the layer of 

soil above the permanently frozen ground that thaws during the 

summer months and freezes again in the autumn. By measuring the depth of the active layer in late summer at the time of 

maximum thaw, we are able to better understand the effects of a 

warming climate on permafrost. The goal of the first two years 

(2009–2010) was to install the first active layer monitoring network for the entire Yukon River Basin (YRB) and to determine 

the feasibility of sustaining and evolving the network within the 

YRB. In August and September 2009, the project was initiated 

and 12 ALN grid sites were installed. In 2010, 8 more sites were 

installed, completing a basin-wide network of 20 sites across 

the YRB (fig. 1).

Problem and Need

Numerous studies indicate that permafrost is thawing 

and the active layer is deepening (Jorgenson and others, 2006; 

Romanovsky and others, 2008; Frey and McClelland, 2009). 

Permafrost thaw will likely lead to changes in groundwater 

flows (Walvoord and Striegl, 2007) and the quantity and quality of the rivers, streams, and lakes (Striegl and others, 2005, 

2007). Moreover, systematic changes in the thickness of the 

active layer may have profound effects on the flux of greenhouse gases, human infrastructure, and landscape processes 

in cold regions. It is critical, therefore, that observational and 

analytical procedures continue over decadal periods to assess 

trends and detect cumulative, long-term changes.

The USGS/YRITWC ALN cooperative project was established with the goal of building an infrastructure conducive to 

long-term observations. Research is currently underway using 

the latest remote sensing technologies to improve the resolution 

of permafrost maps; existing maps were constructed decades 

ago with few data. Remote sensing is a tool for efficiently 

mapping large areas and requires ground-truthed data to verify 

and refine results. The information provided by the ALN will 

provide the necessary ground-truthing and facilitate efforts to 

develop a more accurate permafrost map of the YRB.

Previous Work

Faculty at the University of Alaska–Fairbanks (UAF) 

pioneered permafrost and active layer network studies in Alaska 

through the collaborative development of the global Circumpolar 

Active Layer Monitoring program (CALM). The primary goal of 

CALM is to observe the response of the active layer and nearsurface permafrost to climate change over long (multi-decadal) 

time scales. The CALM observational network, established in 

1991, by 2007 boasted more than 125 participating sites representing multiple countries in both hemispheres. Active layer 

thickness is measured at approximately 60 sites on grids ranging 

from 1 hectare (ha) to 1 square kilometer (km2). Additionally, soil 

temperatures, including permafrost temperature from boreholes, 

are observed at 100 sites following standard CALM protocols 

(http://www.udel.edu/Geography/calm/).

Methods

Site Locations

The location of grid sites was based on several factors. 

First, locations were chosen based on the presence of generally 

continuous permafrost at a depth that can be measured manually 

with a calibrated rod. Second, distribution of sites within the 

YRB must represent the wide range of physiographic regions 

and land cover such as upland, lowland, un-forested, and 

forested areas. Third, the site must be available for community 

involvement and maintenance. The specific location of each 

Figure 1. Locations of Active Layer Network sites within the Yukon 

River Basin in Canada and Alaska.

*

For additional information concerning the Web site, contact Carol Thomas, 

YRITWC: 907-258-3337; cthomas@yrtitwc.com

150° 140° 130° 120°

65°

60°

Digital elevation data available from U.S. Geological Survey,

Earth Resources Observation and Science (EROS) Center,

Sioux Falls, South Dakota

ALASKA

CANADA

Yukon River Basin

0 130 260 520 MILES

0 170 340 680 KILOMETERS

EXPLANATION

Active Layer Network sites

Digital Elevation Model

Elevation (meters)

High: 6009

Low: 1

Yukon River

Tributaries
site within the chosen regions was selected through community participation using community member’s local knowledge 

of permafrost distribution and depth, followed by onsite field 

measurements. Once a site was chosen, latitude and longitude 

coordinates were taken at the four corners of the grid using a 

global positioning system (GPS). Site elevation obtained from 

GPS was also recorded at the center point.

Design

The general project design for the ALN follows protocols from CALM, and further guidance was sought from UAF 

professors who have led their own permafrost studies in Alaska 

in order to supplement data from CALM (Romanovsky, V.E., 

UAF, and Yoshikawa, K., UAF, personal commun., 2009).

With the exception of one site, where a 100-m line configuration was used due to logistical constraints, all sites used 

a 50-m2 square grid in which the depth of the active layer was 

measured at 5-meter (m) intervals for a total of 100 measurements per site. Protocol obtained from CALM suggests a grid 

size of 100 m2; however, a 50-m2 grid was deemed acceptable 

because of difficult terrain and length of time for installation 

(Romanovsky, V.E, UAF, personal commun., 2009). The grids 

were constructed by placing 1-m wooden stakes at 5-m intervals 

along parallel lines, providing consistent spatial measurements 

to run a meter tape to measure along. These stakes also serve 

as place markers to help find the site in the future. Depth of the 

active layer was measured using a calibrated 1.1-m steel metal 

rod with a blunt tip and a T-handle grip. The rod was pushed 

into the active layer until it made contact with the permafrost. 

Contact of the rod tip with the permafrost has a distinct feel to 

the experienced technician. Using this experience, differences 

among other materials, such as rocks and roots, can also be 

distinguished. The depth was measured and recorded on a modified CALM field sheet. To minimize the questionable influence 

of tussocks on the active layer measurement, the measurements 

were made at the lowest surface level within about 30 centimeters (cm) of the designated point.

Each of the 20 ALN sites was equipped with two 

HOBO® S-TMB-M002† soil temperature sensors and two 

HOBO S-SMx-M005† soil moisture sensors. One of each sensor 

was placed at a shallow depth, several centimeters into the surface organic soil, and also at a deeper depth, several centimeters 

above the permafrost. Sites were also equipped with a HOBO 

Pro v2† air temperature sensor placed about 1 m above the 

ground surface. In locations with forest cover, the air temperature sensor was placed on a nearby tree. In cases where there 

were no trees, such as sites in the tundra, the temperature sensor 

was mounted on a wooden stake.

Wires from the sensors were covered with tin foil or plastic 

casing in an attempt to protect the wires from rodents (marmots, 

ground squirrels, mice, and so forth). The soil moisture and 

Carol Thomas, YRITWC, measuring the depth of the active layer in 

Kotlik, Alaska.

Leah Mackey, YRITWC, measures the active layer near Hess Creek 

where it crosses the Dalton Highway, Alaska.

†

The use of brand, trade TM, or firm names in this report is for identification 

purposes only and does not constitute endorsement by the U.S. Geological Survey.

Brett Uhle (front), USGS, and Victor Tonuchuk Jr. (back), Environmental 

Coordinator for the Kotlik Traditional Council, download air temperature 

data at the ALN site near Kotlik, Alaska.
temperature sensors were linked by wires to a HOBO Micro 

Station† data logger and set to record data every 30 minutes to 

be downloaded in one calendar year.

Community Participation

Local participants were engaged in the execution of this 

project, allowing researchers to obtain valuable site-specific information known only by community members. Community participation at each grid location will increase the chances of moving 

toward long-term data collection, which is critical to the objectives 

of the ALN project. Utilizing and expanding the local skill base 

through community participation is a key component to the success 

of the USGS/YRITWC ALN project and will become the focus of 

the project in 2012 and beyond.

Engaging with the communities about the purpose and 

importance of the ALN project is essential to the success of this 

study. During site installations in 2009, students from Fort Yukon 

and Beaver, Alaska, participated in staking out the grid, taking 

active layer measurements, and reading GPS coordinates, giving 

the students an opportunity to learn about the cooperative USGS/

YRITWC ALN project across the YRB. During follow-up site 

visits and new site installation in 2010, USGS and YRITWC staff 

lectured at local schools about the project and involved students 

and teachers in the actual grid installation and measurement when 

possible. When site visits were not possible, classes were taken on 

field trips to participate in experiential learning and install a mock 

grid at a site near the school (see photo, below).

Karonhiakta’tie Bryan Maracle (center), YRITWC, explains how to set up the ALN grid to students 

in Carcross, Yukon Territory, Canada.

References Cited

Frey, K.E., and McClelland, J.W., 2009, Impacts of permafrost 

degradation on arctic river biogeochemistry: Hydrological Processes, v. 23, doi:10.1002/hyp.7196, p. 169–182.

Jorgenson, M.T., Shur, Y.L., and Pullman, E.R., 2006, Abrupt increase 

in permafrost degradation in Arctic Alaska: Geophysical Research 

Letters, v. 33, L02503, doi: 10.1029/2005GL024960, 4 p.

Romanovsky, V.E., Grosse, G., and Marchenko, S., 2008, Past, 

present and future of permafrost in a changing world, in Annual 

Meeting of the Geological Society of America, Houston, TX, 

October 5–9, 2008, Proceedings: Geological Society of America 

Abstracts with Programs, v. 40, no. 6, abs. 264-4.

Striegl, R.G., Aiken, G.R., Dornblaser, M.M., Raymond, P.A., 

and Wickland, K.P., 2005, A decrease in discharge-normalized 

DOC export by the Yukon River during summer through 

autumn: Geophysical Research Letters, v. 32, L21413, 

doi:10.1029/2005GL024413, 4 p.

Striegl, R.G., Dornblaser, M.M., Aiken, G.R., Wickland, 

K.P., and Raymond, P.A., 2007, Carbon export and cycling 

by the Yukon, Tanana, and Porcupine Rivers, Alaska, 

2001–2005: Water Resources Research, v. 43, W02411, 

doi: 10.1029/2006WR005201, 9 p.

Walvoord, M.A., and Striegl, R.G., 2007, Increased groundwater to stream discharge from permafrost thawing in the 

Yukon River basin—Potential impacts on lateral export of 

carbon and nitrogen: Geophysical Research Letters, v. 34, 

L12402, doi:10.1029/2007GL030216, 6 p.

Challenges and Future Work

Building robust infrastructure is key, 

and that goal was achieved in 2009 and 

2010. The focus of the project is now on 

monitoring and maintaining the sites. The 

most challenging part of any long-term 

research project is ensuring its continuation. Changes in or the discontinuation 

of funding sources, staff, and research 

priorities are all obstacles to successful 

long-term research. An advantage of the 

ALN project is its simplicity—site visits 

occur only once a year in the late summer 

when the active layer is at its maximum 

depth. During the site visit the grid is measured and sensor data are downloaded to 

a computer. The sensors are reset, batteries are changed, and if needed, damaged 

sensors are replaced as part of maintenance. Year three of the ALN project will 

focus on training community members as 

volunteer technicians to assist in the basic 

maintenance and annual measurements as 

required by CALM protocol.
Acknowledgments

The USGS and YRITWC thank the Indigenous Observation Network (ION) field technicians that facilitated the engagement of 

local participation in the ALN study and completed successful installations at selected grid sites across the basin. Without their assistance the ALN would have been considerably more difficult. Special thanks to Dr. Vladimir Romanovsky and Dr. Kenji Yoshikawa of 

the University of Alaska–Fairbanks for the time they took to share their experiences and advice throughout the initiation of the project

Paul F. Schuster

U.S. Geological Survey

3215 Marine Street, Suite E-127

Boulder, CO 80303

Phone: 303-541-3052

Fax: 303-541-3084

Email: pschuste@usgs.gov

Carol Thomas

Yukon River Inter-Tribal Watershed Council

725 Christensen Drive, Suite 3

Anchorage, AK 99501

Phone: 907-258-3337

Fax: 907-258-3339

Email: cthomas@yritwc.org

Karonhiakta’tie Bryan Maracle

Council of Athabascan Tribal Governments

Post Office Box 33

Fort Yukon, AK 99740

Email: bmaracle@catg.org

For additional information contact:

At the ALN site near Chevak, Alaska.

Left to right: Brett Uhle, USGS; Carol Thomas, YRITWC; 

Deborah Friday-Aguchuk, Chevak Native Village 

Environmental Program; Cynthia Paniyak, Chevak 

Native Village Environmental Program.