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Barrow Sea Ice Mass Balance Site 2011

Barrow Sea Ice Thickness and Sea Level

The mass balance probe recorded data from 24 January until 7 June 2011.

The latest measurements available are of Jun 07, 2011, 11:15 AM AKDT:
Air temperature:
–1 °C, 31 °F
Ice thickness:
1.42 m, 4 ft 8"

Ice thickness may be incorrect since June 1, 2011 due to melt at the site.
See metadata for details.


The Mass Balance Probe was deployed on landfast sea ice in the Chukchi Sea at Barrow, Alaska on January 24, 2011, a calm and sunny day of balmy −41 °C. At the time, ice thickness was 0.85 m (almost 3 ft) and snow depth was 0.05 m (2 inches). Ice thickness, snow depth, sea level, and temperature profiles are recorded every 15 minutes, transferred to Fairbanks, processed and presented online with approximately 5 minutes delay. The probe will be recovered from the ice prior to break-up. Recovery is likely to take place in June 2011.

sketch of mass balance probe

The mass balance site consists of distance and temperature sensors. Acoustic sounders are used to measure the distance to the underside of the ice (for ice thickness), the bottom of the ocean (for sea level and tides), and the snow surface (for snow depth), respectively. Three snow depth measurements are recorded, one of which is co-located with the ice thickness measurement. Apart from air temperature and relative humidity, a vertical temperature profile through air, snow, ice, and water is measured. Measurements are performed every 15 minutes and transferred to a base station in Barrow through a 900 MHz UHF radio link, from where they are sent through an internet connection to Fairbanks for further processing. Measurements are taken every 15 minutes.

A detailed description of the set-up is available in the metadata file (BRW11_MBS_metadata.txt). Raw data (BRW_MBS_2011_raw.txt) and processed data (BRW_MBS_2011.txt) are available. Please read the metadata file (BRW11_MBS_metadata.txt) before using them. Note that data format and metadata file may change during the season without notice. The data logger program used in seasons 2010 and 2011 (i.e., last year and this year) is available here. The script used to convert raw data from the data logger into something meaningful is here.

Plots on this page are generated from automatically processed data prior to human quality control.

The map shows the location of the 2011 mass balance site. Instruments are located on a patch of undeformed landfast sea ice at Barrow, Alaska, 156.545376° W, 71.366885° N. The instruments are approximately 1 km (1/2 mile) offshore, North of Niksiuraq, the hook at the end of the road to Point Barrow. Locations in previous years are shown on this map.

The optical instruments of the Alfred Wegener Institute (AWI) are located in the immediate neighborhood of the mass balance instruments (enlarge map for details).

Measurements at the mast

This plot shows the air temperature, snow depth, ice thickness and water depth measured at the mast of the Mass Balance Site. Snow depth and ice thickness are derived from acoustic sounders that take one measurement every 15 minutes. The accuracy is about ±1 cm (±1/2 inch). Data are filtered for this plot; unfiltered data are shown below.

Temperature profile

This is the temperature profile through air, snow, ice, and water. The grayed area indicates the position of the ice (bottom may be off by 0.1 m). The bounds of the red funnel are the highest and lowest temperatures recorded during the past 24 hours. The black line with data points (spaced 0.1 m, 4 inches) is the latest temperature profile. Air, snow, ice, and water can often be discriminated easily in winter and early spring: daily temperature swings are more pronounced in the air than in the snow; the temperature profile in the ice is usually linear and steeper than in the snow; the temperature in the water is approximately independent of depth. Towards summer the ice acts as a heat sink with the coldest temperature registered inside the ice rather than in the air.

Temperature measurements are accurate to approx. ±0.2 °C. Further, measurements in summer may be affected by solar heating of the probe.

Water temperature

This figure shows the water temperature approx. 1 to 2 m below the ice as detected by the bottom-most thermistor at the string of temperature sensors (blue), and by the thermistor 30 cm (1 ft) above (red). Data are smoothed by a running average filter with 6 hour window. The temperature readings are only crudely calibrated to ±0.2 °C. Note that both sensors may be heated by incident solar energy. The line in light gray is the tidal signal.

Relative humidity

These are air temperature and relative humidity, both measured by the Campbell CS500 probe enclosed in a radiation shield on the pinger mast.

Depth and thickness soundings

This plot shows the air temperature, snow depth (three locations), ice thickness and water depth measured at the mast at the Mass Balance Site (see figure above). Snow depth and ice thickness are derived from acoustic sounders that take one measurement every 15 minutes. The accuracy is about ±1 cm (±1/2 inch). The colored lines are snow depth and ice thickness data smoothed by a median filter with a 24-hour window. The actual measurements are shown in light gray underneath.

A preliminary comparison of these water depth measurements shows that they are comparable to tide gauge data until the onset of melt at the end of May.

Snow depth and ice thickness are spot measurements rather than aerial averages. There are snow dunes on the ice that may be 60 cm (2 ft) deeper than the thinnest snow; the measurements by the pingers are probably somewhere between the extremes. Similarly, the thickness of level ice varies in the general area surrounding the Mass Balance Probe.

Temperature Probe

The temperature probe measures the vertical temperature at 10 cm (4 inches) intervals, starting 70 cm (2 ft) above the ice surface at the time of deployment. This plot shows those temperature measurements, i.e. temperature in air, snow, ice, and water. In winter and spring, the coldest and warmest temperatures are measured in the air and water, respectively. In summer, the air temperature exceeds the melting point and snow and ice melt both from the top and from the bottom. The current temperature profile is shown above.

Temperature Profile

Color-coded temperature vertical profile through air, snow, ice, and water. Also indicated are are the position of the ice bottom and snow surface measured at the pinger mast.

Supply voltage

The Mass Balance Site is powered by two lead acid batteries attached to a wind turbine. On windy days (10 knots and above) power is delivered by the turbine and the batteries are being charged. The charge voltage increases with wind speed but is capped by a temperature-compensated charge controller. On windy days, the voltage should be above 14 V, indicating that the batteries are being charged. On windless days, the battery voltage can be used to estimate the available charge. Currently, the voltage is 11.68 V. A voltage of 10.5 V is typical for drained lead acid batteries. This is higher than the minimum voltage required for the data logger (9.6 V) and for the UHF radio (6 V). Our goal is to maintain the battery voltage above 11.5 V.

This project is supported through the Alaska Ocean Observing System (AOOS) with logistical and technical support provided by the Barrow Arctic Science Consortium (BASC). We also gratefully acknowledge the Arctic Slope Regional Corporation (ASRC) for supporting installation of the webcam and radar. This material is also based upon work supported by the National Science Foundation under Grant No. OPP-0856867. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).

Contact: Chris Petrich (