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Low-Cost Expendable Buoys for Under Ice Data
Collection
D. Langis, P.J. Stabeno, C. Meinig
Pacific Marine Environmental Laboratory
National Oceanic and Atmospheric Administration
Seattle, WA USA
daniel.p.langis@noaa.gov; phyllis.stabeno@noaa.gov;
christian.meinig@noaa.gov
C.W. Mordy, S.W. Bell, H. M. Tabisola
Joint Institute for the Study of Atmosphere and Ocean
University of Washington; and
Pacific Marine Environmental Laboratory
National Oceanic and Atmospheric Administration
Seattle, WA USA
mordy@uw.edu; swbell2@uw.edu; hnmac@uw.gov
Abstract—The NOAA Pacific Marine Environmental
Laboratory (PMEL) has designed a new, low-cost, expendable
under-ice buoy capable of collecting oceanographic data at the
water-ice boundary to address gaps in knowledge during these
critical periods. The buoys are designed to be deployed from a
research vessel during the ice-free season, where they collect data
while anchored to the seabed until the surface is completely
covered in sea ice. At a designated time for each device, a release
is triggered, which allows the buoy to ascend and be buoyant just
under the ice, collecting a vertical profile of the water column
during its ascent. The buoys remain at the ice-water interface
collecting data, until break-up or melting of sea ice, when their
data are transmitted to shore. Preliminary versions of the
instrument were deployed in the Chukchi Sea in 2015
(Generation 1) and the Bering Sea in 2017 (Generation 2),
collecting data on temperature, depth, and photosynthetically
active radiation (PAR). These deployments successfully
demonstrated the viability of the low-cost design, its robust
nature, and its ability to provide high-quality data. Ongoing
developments (Generation 3) include measurement of
fluorescence and collection of daily images for situational
awareness and to assess the presence of ice-associated algae.
Onboard GPS provides precise location data from open water,
and all data are transmitted to shore using Iridium Short Burst
Data (Generations 2 and 3). These compact instruments are
optimized for use in the relatively shallow waters of the
continental shelf (up to 100 m depth) in the Bering and Chukchi
seas. Their cost advantages can be best leveraged to provide
improved spatial coverage over this enormous area, where
observations are typically sparse. These under-ice buoys are one
of several new technologies being developed as part of the
Innovative Technology for Arctic Exploration (ITAE) project—a
collaborative effort between scientists and engineers at NOAA
and the University of Washington. Collectively, they represent a
unique opportunity to improve the basic understanding of the
changing Arctic environment and to cost-effectively monitor
future changes.
Keywords— Lagrangian, platform, technology, ocean
observation, Arctic, sea ice, ecosystem monitoring, instrumentation,
NOAA, PMEL, ITAE
I. INTRODUCTION
A. The Need for Under-Ice Measurements
Conditions directly under Arctic sea ice during spring and
early summer months are largely a mystery, but it is clear that
they play a critical role in shaping one of the world’s most
productive ecosystems. Massive phytoplankton blooms have
been identified under Arctic sea ice [1], but the timing and
prevalence of such events are unknown [2]. Additionally, the
character of the ice-edge environment is changing with the loss
of multiyear sea ice and overall thinning of the ice matrix,
which has complex implications for marine and terrestrial
ecological dynamics [3]. Improved understanding of the
processes that govern sea-ice evolution in the Marginal Ice
Zone (MIZ) is needed to improve sea-ice models, inform
planning for transpolar shipping, and formulate responses for
coastal communities [4]. However, the dynamics associated
with sea-ice retreat and advance in the MIZ of the Arctic pose
significant observational challenges.
Transition periods during ice retreat and ice advance
exhibit the most dynamic changes in the ecosystem, but are
difficult to measure because both ships and aircraft struggle to
provide access to the region [4]. The small number of ship-
based observations are costly due to the limited availability of
ice-capable vessels, which are required to provide access
during these key periods. Even with the inclusion of ship-based
measurements, a wide network of moorings and autonomous
systems is necessary to capture the variability inherent in the
Arctic [4].
Funding for Innovative Technology for Arctic Exploration is provided by
N
OAA Research with in-kind support for the under-ice buoy from the
Ecosystems and Fisheries-Oceanography Coordinated Investigations program
at NOAA/PMEL. This publication is partially funded by the Joint Institute for
the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative
Agreement NA15OAR4320063.
During winter, fast-moving ice keels up to 20 m deep in the
northern Bering Sea [5] and greater than 30 m deep in the
Chukchi Sea [6] have been recorded. Instruments on typical
subsurface moorings must be kept below these thresholds to
prevent them from being dragged or damaged by ice keels.
Innovative methods must be used to access the upper water
column during winter and transition periods. Arctic winches
have been designed to address this problem by tethering the
subsurface mooring to an instrumented float, which
periodically rises to the underside of ice (or surface) to measure
the upper water column. However, the tethered float can be
destroyed by ice keels sweeping past. Mechanical complexity
also increases cost ($130,000 per system) and logistic
demands, thus limiting spatial coverage due to the number of
systems that can be deployed. Ice-tethered profilers (ITPs),
called the ‘Argo of the Arctic’, are another system capable of
measuring the upper water column [7]. ITPs are typically
deployed on multiyear ice floes through a hole that has been
augered in the ice. They are designed to collect vertical profiles
of data along a tether that can be up to 800 m in length. Efforts
have been introduced to allow for open water deployments and
to modify profiling parameters for shallow water drift, but
almost all data collection efforts for ITPs are limited to the
deep water of the Arctic basin where they are most cost-
effective, since landing and drilling holes on floes are required,
and they are also less vulnerable to ice dynamics seen in the
MIZ [7].
Autonomous platforms—such as gliders, profiling floats,
and drones—can provide cost-effective monitoring and
expanded spatial coverage of the ocean. Presently, many are
being utilized and tested in Arctic observational networks [4].
However, accessing the under-ice regime is still problematic
for these systems. Few underwater gliders have the ice-
avoidance capabilities that are especially necessary in shallow
water, and Autonomous Surface Vehicles cannot transit into
the ice pack. Profiling floats, such as Argo or ALAMO, can be
deployed in the ice-free season and collect measurements
during the fall transition period (ice advance), but these
Lagrangian systems lack the station-keeping ability needed to
stay at a desired deployment location and have not yet been
proven to work directly under arctic ice.
B. Design Concept for an Under-Ice Buoy
NOAA’s under-ice buoys are made to fill a specific gap in
technology: to provide a cost-effective method of monitoring
conditions directly under ice, primarily in the MIZ during
springtime ice retreat. The instruments are optimized for use in
shallow waters (up to 100 m), where primary productivity is
high and conditions are highly dynamic, but historical
observations are scarce.
The buoys are designed to be deployed from a research
vessel during the ice-free season, where they collect data while
anchored to the seabed until the surface is completely covered
in sea ice. A release triggered at a designated time for each
device allows the buoy to ascend and bob just under the ice,
collecting a vertical profile of the water column during the
ascent. The buoys remain under ice collecting data until break-
up or melting of sea ice, when their data are transmitted to
shore via Iridium Short Burst Data (SBD). Several design
requirements drove the concept for these devices.
They must be able to access the regime directly under sea
ice during springtime ice retreat. The delayed release concept
allows the instruments to be deployed without the need for
aircraft or an ice-capable vessel. One drawback to this
technique is that the timing of release is set months earlier,
before deployment, and buoys cannot respond to any unusual
occurrence (e.g. early ice retreat). The compact, lightweight
design chosen for these instruments allows them to be
deployed without any specialized equipment from nearly any
vessel, reducing logistic constraints and providing more
possibilities for ships of opportunity.
In order to access and continuously sample the springtime
retreat, the instruments must be robust. They must be able
survive situations such as being frozen in ice, being caught
between compressing and rafting floes, or being pushed onto
the surface of an ice floe where temperatures can reach –20 °C
or colder. The physical shape and configuration of the
instrument plays a critical role in survivability, as does
ensuring that all sensors and any antennas are extremely well-
protected. The buoys encapsulate all sensors and antennas
within a spherical housing to allow the instruments to ‘ride’
smoothly under ice. A counterweight mounted at the bottom of
a vertical frame acts as a pendulum to keep the buoys upright
at all times. These Lagrangian platforms are designed to drift
easily with ice floes, eliminating any tethers that could possibly
be severed by ridging and shifting ice.
Even the most robust instruments deployed near the surface
in the MIZ during springtime ice retreat will be exposed to
significant risk due to ice dynamics; thus, the possibility of
instrument loss cannot be eliminated. This risk must be
accounted for and mitigated, either by providing a method of
data recovery or reducing the impact of such losses. The low
per-unit cost of these expendable instruments is advantageous
as a large number of units can be deployed and a small
percentage of instrument loss can be tolerated more easily than
the potential loss of large, expensive systems. The expendable
design and simple deployment procedure also reduce total life-
cycle costs by minimizing required ship time and labor.
II. GENERATION 1: SATELLITE TAG PROTOTYPE
A. Design
The first step in development was to construct prototype
instruments and test the concept of an expendable under-ice
buoy. This concept was tested in 2015 by using commercially
available satellite tags to measure, record, and telemeter data,
and building a superstructure around the tags to provide
protection and flotation. In this initial test, temperature,
photosynthetically active radiation (PAR), pressure, and tilt
data were collected.
Satellite tags were an excellent basis for prototype
instruments as they are robust, can provide dynamic profile
data and offer a commercial solution during development
before investing in the engineering.
Satellite tags, developed by the University of St. Andrews’
Sea Mammal Research Unit (SMRU) were used because of
their high-quality data. SMRU also provided support to
integrate a unique PAR sensor into the tags and to modify their
sampling schedule for NOAA’s under-ice application.
Fig. 1 shows a diagram of the prototype under-ice buoy.
The satellite tags were each attached to a trawl float for
buoyancy. The floats were covered by a ‘hard-hat’ shell for
physical protection and fitted with a counterweight to keep
them upright. The flotation unit was rigged to an anchor, drop
weight, and two galvanic timed releases. After the units were
deployed, the lower (primary) release would corrode after a
few days to release the unit from the seafloor. After several
more days, the upper (secondary) release would corrode,
making the buoy more positively buoyant and providing extra
freeboard to facilitate data transmission after emerging from
the ice.
B. Deployment (2015)
Two prototype buoys were deployed in the Chukchi Sea
from the USCGC Healy in July 2015 (Fig. 2). Buoy-1 was
deployed on 11 July at 71.7° N, 160° W and Buoy-2 was
deployed on 14 July at 70.9° N, 149.7° W. In each case, the
ship was in eight-tenths to nine-tenths ice cover, approximately
40 km from the ice edge. The prototype buoys were designed
to anchor on the bottom for two days before releasing under the
ice and collecting a profile of temperature and PAR as they
surfaced. They were expected to measure conditions under the
melting ice for a few days, or perhaps weeks, and then transmit
data to shore once free of ice. This deployment was designed to
test the feasibility of the delayed-release concept, quality of
satellite-transmitted data, and survivability of the buoys under
sea ice.
Buoy-2 was deployed on 14 July and worked as expected.
The buoy was anchored for several days before beginning to
record data on 16 July. Bottom temperatures at the deployment
site were fairly constant at approximately –1.8°C (Fig. 3),
which is typical bottom temperature in these waters. Upon
release on 17 July, the buoy rose to the surface and collected a
vertical profile. The temperature was relatively constant until
reaching a depth of approximately 2 m, when temperature
began to increase, reaching –1 °C at the surface (Fig. 4). While
anchored to the bottom, a PAR signal was just discernible
(Fig. 3). As the buoy rose through the water column, PAR
increased as expected even though it was released during the
darker part of the day. When it reached a depth of
approximately 3 m, PAR unexpectedly began to decrease. This
small decrease in PAR (relative to the large daily changes
observed at the surface) is most likely a consequence of the
large spatial variability in ice thickness and/or presence, and
perhaps spatial variability in ice-associated particulates (e.g.
microbial communities). Thus, as the buoy rose, it entered into
the shadow of a floe and eventually came to rest under that
floe. Over the next four days the buoy remained trapped under
the ice. During this time, a weak PAR signal is evident (Fig. 3).
Eventually, on 21 July, the floe either melted or broke apart;
the buoy arrived at the surface and transmitted the data it had
been collecting over the past six days. After 21 July, a strong
diurnal signal is evident in both temperature and PAR. It must
be noted that the thermistor was no longer measuring ocean
temperature but was exposed to the atmosphere at this point.
The large variations in temperature are consistent with the air
space between the trawl float and hard-hat shell being heated
by sunlight. The PAR signal saturates at 650 µmol photons
m
2
s
-1
, which is the upper limit of the sensor’s measurement
range.
Fig. 1. Schematic of under-ice buoy prototype: (1) ‘hard hat’ casing; (2)
satellite tag; (3) trawl float; (4) counterweight; (5) secondary release; (6)
drop weight; (7) primary release; and (8) anchor.
Fig. 2. Map of deployment locations. Buoy-1 was deployed on 11 July
2015 and Buoy-2 was deployed on 14 July 2015. The hatched area
represents Multisensor Analyzed Sea-Ice Extent (MASIE) on 10 July
2015. The red and green circles indicate deployment sites. The lines
indicate drift track during transmission.
Buoy-1 was deployed on 11 July 2015, but did not transmit
any data in the summer of 2015. Instead, it transmitted data 13
months after deployment, approximately 560 km west of the
deployment location (Fig. 2). A clock error of almost 4 months
was evident in the raw data, and was corrected based upon the
data transmission date. Results shown in Fig. 5 are consistent
with the following scenario. No data were recorded from
deployment through the next 3+ months, so the time series
begins at the end of November, with the buoy apparently
caught in the ice. It then transitioned to more than a meter
above the water surface, which could have been the result of
rafting of one ice floe over another. From five years of Pacific
Marine Environmental Laboratory (PMEL) experience with
satellite-tracked drifters, when caught in sea ice, it is not
uncommon for the drifters to only intermittently communicate
(no transmissions for weeks at a time) with satellites. It is
possible that Buoy-1 was on its side or shaded by ice so that no
data transmissions occurred during the period in December and
January when it appeared to be above the ocean surface. The
very cold temperatures are further evidence that the buoy was
trapped on an ice floe and exposed to air. The temperature
stops decreasing at –5°C, when the sensor reaches the lower
limit of its measurement range. In late January, the sharp
change in pressure suggests the ice floe changed suddenly (e.g.
perhaps turning on its side or another floe rafting on top of it),
forcing Buoy-1 several meters into the water, where it
remained until the following summer. Between June and late
August 2016, the buoy shoaled from 4.5 m to 2.3 m, at which
point it suddenly surfaced into open water and transmitted data
to shore.
C. Assessment
While the prototype was successful in meeting the basic
requirements of an under-ice buoy, the design had several
Fig. 3. Plot of temperature (red) and PAR (black) for Buoy-2. Vertical dashed lines indicate times when the buoy was released from the anchor (17 July)
and when it surfaced to transmit data to shore (21 July). The horizontal dotted line is the freezing point of seawater having a salinity of 33 (–1.81°C). Note
that the time axis is UTC and does not reflect solar days.
Fig. 4. The vertical profile of temperature (red) and PAR (black) on
17 July when Buoy-2 was released from the anchor.
Fig. 5. Plot of depth (blue) and temperature (red) for Buoy-1. Vertical
dashed lines indicate times when the buoy became submerged (1/28/16) and
when it surfaced to transmit data to shore (7/30/2016). The horizontal lines
indicate the sea-surface (dashed) and the freezing point of seawater (dotted)
with salinity of 33 (–1.81°C).
drawbacks. Satellite tags were shown to be an effective method
during initial development, but not for long-term use due to
per-unit-cost ($4,300 per tag). The compact design of satellite
tags, while advantageous for marine mammal applications,
limited the available power, endurance, and potential sensors
when evaluating long-term (1+ year) under-ice applications.
The most successful element of the prototypes were their
survivability. The spherical shape of the buoy and protected
antenna proved to be incredibly robust, as Buoy-1 survived two
ice retreat seasons and one ice advance season in the Chukchi
Sea.
III. GENERATION 2
A. Design
The second generation of under-ice buoy was equipped
with sensors to measure depth (±0.21 m accuracy), temperature
(±0.01°C) , PAR (±3% accuracy), and tilt; as well as GPS and
Iridium SBD modules. A number of cost-saving design
features were utilized to achieve a cost per instrument of less
than $3,000. Features included low-cost pressure housings,
commercial off-the-shelf components, and custom analog-to-
digital circuitry for sensors. Fig. 6 shows pictures of the
assembled buoys and Table 1 shows a list of the major
components, and sensors, as well as costs and descriptions of
each.
TABLE I. L
IST OF MAJOR COMPONENTS FOR GENERATION
2
BUOYS
Component(s)
a
Cost
b
Details
Trawl Float
(Pressure
Housing)
$33 12” ABS Trawl Float;
27.5 lb. nominal buoyancy
PAR Sensor $364
Skye Instruments TAG-PARQ
Sensor; ±3% accuracy,
0 to 2000 μmol m
–2
s
–1
Temperature
Sensor $10
Custom NTC Thermistor Probe
±0.01°C accuracy, -5°C to
+70°C
Pressure
Sensors $125 ea
Two Keller PA-4LD Pressure
Sensors; 4.5 cm accuracy
(at 0°C), 0 to 30/100 m
Iridium Module
and Antenna $330 RockSeven RockBLOCK Mk2
Iridium 9602 Module
Burn Wire
Release $165
Sub-Sea Sonics TR-45 Timed
Release; 40 lb. Max. Load,
170 Day Limit
Micro-
Controller $38 Arduino MEGA 2650
Battery Pack $56 Custom 9V, 28A-h Alkaline
Pack
GPS Module
and Antenna $35 Alpha Micro PA6H Module
PCB Assembly $350 Custom PCB Assembly
Mechanical
Assembly $1,100
Custom Machining for
Load-Reducing Mechanism and
Sensor Integration
TOTAL $3,000
Total cost (Note: not all
components are listed in
this table)
a.
Only major components listed
b.
Approximate costs
Fig. 6. Left: Under-ice buoy as viewed from above showing (1) pressure sensors, (2) PAR sensor, and (3) temperature sensor. GPS
and Iridium antennas are embedded under the cap to prevent them from being damaged by ice. Right: Under-ice buoy as viewed from
side showing (4) pressure housing, (5) “burn wire” timed release, and (6) load-reducing mechanism. Diameter of housing is 34 cm and
height from top of buoy to bottom of frame is 90 cm.
B. Deployment (2017)
In September 2017, five Generation 2 under-ice buoys were
deployed in the Bering Sea approximately 30 km southeast of
St. Matthew Island in 68 m of water (Fig. 7). Historically, sea
ice arrives at this location in December and persists into May.
From February to March, average areal ice concentration
exceeds 65% [8]. Noting this, the buoys were programmed
with release dates between 20 February and 15 March 2018.
The expectation was that the instruments would surface under
thin, first-year ice and be transported southward by the
prevailing winds. The buoys were expected to emerge from the
ice within a few weeks as the leading edge of the ice
encountered warmer water to the south and melted.
Unfortunately for this experiment, for the first time in the
satellite era (starting 1972), there was no ice at the deployment
site during winter. In fact, the most notable aspect of the 2017
to 2018 winter sea-ice extent was the persistently low ice
extent in the Bering Sea [5].
Because of the absence of ice at the site, four of the five
buoys (Buoys 4–7) surfaced in open water. They transmitted
complete sets of data via Iridium SBD within 8–12 hours of
surfacing. It is unknown why the other buoy (Buoy-3) failed to
transmit any data. All four of the successful buoys continued to
drift at the surface in the Bering Sea for several months,
transmitting SBD messages with at least an 80% transmission
success rate in seas ranging from 2 to 7 on the Beaufort scale,
as determined by wind speed in the region.
In Fig. 8, all four time series of temperature are plotted and
the release time of each buoy is indicated by a dotted vertical
line. These data provide a snapshot of subsurface conditions
many months before other observations from ships and
moorings in the region became available. Note that while there
are moorings in the vicinity, they do not transmit in real time
and would not be recovered until September 2018. Also shown
in Fig. 8 are bottom temperatures for two years (2008/2009 and
2016/2017) from a nearby, long-term mooring, M5 (59.91°N,
171.73°W). (Details of the mooring can be found in [8].) Note
that 2008 and 2009 were cold years with extensive ice, while
2016 was the warmest year on record with no ice on the
southern shelf. The year 2017 was colder with ice arriving late.
The maximum ice extent in 2009 and 2017 is shown in Fig. 7.
The general patterns in the three time series shown in Fig. 8
are similar. In late summer, the water column is two-layered,
with a warmer, fresher surface layer overlaying a colder, more
saline bottom layer. As the warm surface waters are mixed
downward by fall storms, bottom temperatures increase and the
water column becomes well mixed. For these three time series,
Fig. 7. Map showing the locations of the 2017 under-ice buoy
deployment location (circle) and the M5 long-term mooring. The hatched
area shows 2018 ice extent from Multisensor Analyzed Sea-Ice Extent
(MASIE). Maximum ice extent in 2018 was the lowest on record in the
Bering Sea. Maximum ice extent for 2017 (blue line) and 2009 (red line)
are shown for comparison.
Fig. 8. Plot of seasonal bottom temperatures near St. Matthew Island in the Bering Sea. Data from 2008/2009 (pale blue) and 2016/2017 (pale red)
are from a long-term mooring (M5). Data from 2017/2018 (darker colors) are from four buoys anchored north of the M5 mooring. These buoys were
sequentially released beginning in early March. Vertical dashed lines indicate times when the buoys were released (color-coded to match the time
series of each unit in Fig. 9). The grey horizontal line is the freezing point of seawater with a salinity of 33 (–1.81°C).
this occurred in mid-October 2008, early November 2016, and
early December 2017. At these latitudes the water column
begins to cool (net heat flux into the atmosphere) sometime in
September. Once the water column becomes well mixed,
cooling is evident in the bottom temperatures. The arrival of
ice cools the surface water to –1.7 °C and it can take a week for
this colder, fresher water to be mixed to the bottom. The arrival
of ice is evident in the two M5 time series (early January 2009
and early March 2017). The absence of sea ice in 2018 resulted
in bottom temperatures in early March to be approximately
2.8 °C warmer than usual. These changes in bottom
temperatures are known to have dramatic effects on the
ecosystem of the Bering Sea [9, 10].
The vertical profiles (Fig. 9) provided snapshots of the
water column during a time when no other in situ
measurements were available. At first the water column was
well mixed. This was followed by an intrusion of warmer water
on the bottom and cooling of the near-surface water. To remain
stably stratified, the near-surface water must have been fresher
than the deeper water. PAR provided little unexpected
information; for instance, there was no discernable light signal
at the bottom (68 m).
C. Assessment
Although the instruments did not surface under ice as
desired, their functionality and low-cost design proved
successful. The major innovations in the Generation 2 buoys
were the custom sensor package and software, implementation
of burn-wire releases, and the addition of GPS and Iridium
SBD modules.
The custom sensor package and software provided high-
quality data and a reliable sampling routine. Utilizing burn-
wire releases with the main instruments having independent
clocks provided accurate timing for release and a dependable
method for profile collection. The high success rate of SBD
transmissions, even in open seas with moderate to heavy sea
states, demonstrated that the buoys’ protected antennas still
provided dependable satellite communication.
IV. GENERATION 3: ON-GOING/FUTURE DEVELOPMENT
A. Design Improvements
Based on the lessons learned from Generation 2 under-ice
buoys, a number of improvements have been integrated for
Generation 3 buoys, which will be deployed over winter
2018/2019. These improvements, discussed in detail below,
will leverage the under-ice buoys’ unique capabilities to access
and monitor conditions under first-year sea ice common in the
Bering and Chukchi seas. Fig. 10 provides a section view of a
3-D model for Generation 3 under-ice buoys; Table 2 lists the
major components and sensors, as well as costs and
descriptions of each.
TABLE II. L
IST
O
F
M
AJOR
C
OMPONENTS
F
OR
G
ENERATION
3
Component
a
Cost
b
Details
Trawl Float
(Pressure
Housing)
$33 12” ABS Trawl Float;
27.5 lb. nominal buoyancy
PAR Sensor $364
Skye Instruments TAG-PARQ
Sensor; ±3% accuracy,
0 to 2000 μmol/m
–2
s
–1
Temperature
Sensors $67 ea
US Sensor NTC Thermistor
Probes; ±0.01°C accuracy,
-5°C to +70°C
Pressure
Sensor $117
Keller PA-4LD Pressure Sensors;
4.5 cm accuracy (at 0°C),
0 to 100 m
Iridium
Module and
Antenna
$330 RockSeven RockBLOCK Mk3
Iridium 9603 Module
Burn Wire
Release $750
DBV Technology Burn Wire
Release; 40 lb. Max. Load,
170 Day Limit
Micro-
Controller $38 Arduino MEGA 2650
Battery Pack $95 Custom 9V, 42A-h Alkaline Pack
GPS Module
and Antenna $35 Alpha Micro PA6H Module
PCB
Assembly $350 Custom PCB Assembly
Mechanical
Assembly $600
Custom Machining for Load-
Reducing Mechanism and
Sensor Integration
Fluorometer
(Optional) $1,600 Turner Cyclops Fluorometer
TOTAL $3,000
c
Total cost (Note: not all
components are listed in
this table)
a.
Only major components listed
b.
Approximate costs
c.
Total does not include the optional fluorometer.
Fig. 9. Vertical profiles of temperature from each of the under-ice
buoys. Note that at the surface the buoys were exposed to the air.
A Turner Cyclops fluorometer was integrated into the
system and will provide measurements of chlorophyll
fluorescence: an indicator of phytoplankton biomass. These
data will be used to better understand the timing and extent of
under-ice phytoplankton blooms [1, 2]. The fluorometer is an
optional sensor. Because of its relatively high cost, the buoys
are designed so that it can be easily removed. One under-ice
buoy equipped with fluorometers will be deployed in August
2018 from the USCGC Healy and a second in October 2018
from the NOAA Ship Oscar Dyson.
Once free of the ice, thermistors mounted on the top of the
buoy no longer record sea surface temperature (SST). To
continue obtaining valuable SST measurements after the buoys
are free of ice and drifting in open water, a SST probe was
integrated on the underside of the trawl float. The probe is
approximately 18 cm below the waterline, which is comparable
to SVP drifters [11]. NOAA’s under-ice buoys will provide a
unique opportunity to obtain accurate SST measurements in the
Arctic in the weeks and months following sea-ice retreat.
These data can be used to aid in ground-truthing satellite
estimates in a region where SST measurements are scarce.
A low-cost serial camera module has also been added for
situational awareness and to assess the spatial patterns of ice-
associated algae. The microCAM-III is a low-power module
and includes an on-board JPEG compression chip that
dramatically reduces the amount of data that must be
transmitted via SBD, while still providing full-color images
(160 × 128 to 640 × 480 resolution). An earlier version of the
microCAM-III was selected as the optimal solution for cubeSat
(http://www.cubesat.org/) missions based on many factors
including price, power consumption, simple interface, wide
operating temperature range, and compression capabilities
[12]. These are also driving factors in NOAA’s low-cost under-
ice buoys, making the microCAM-III an ideal choice for this
application.
Lastly, an improved burn-wire release mechanism was
needed to extend the duration from deployment to release
beyond 170 days. This is especially critical for deployments in
the Chukchi Sea, where research cruises typically occur in the
ice-free or low-ice months of August and September, but
release of the under-ice buoys may not be desired until May or
June. A new burn-wire mechanism, developed by DBV
Technology will be tested in the Chukchi Sea during the 2018–
2019 deployments. The additional cost of the new release
mechanism is negated due to its higher load limit, eliminating
the need for the load-reducing mechanism used on Generation
2 buoys.
B. Future Endeavors
NOAA’s under-ice buoys are only one element of a wide
network of observing systems for assessing and monitoring
changing conditions in the Arctic. These buoys provide a tool
for expanding measurements in the harsh environment of the
Arctic. Their innovative and relatively inexpensive design
provides opportunity for near-surface measurements and
greater spatial sampling to complement moorings, ice-tethered
instruments, and autonomous vehicles.
In order to fully assess physical, biological, and chemical
conditions under sea ice, a more extensive sensor suite and
improved vertical resolution are necessary. However, many
sensors, such as conductivity, oxygen, and nitrate, are too
expensive to integrate into these instruments. Opportunities for
integrating new low-cost sensors and developing a low-cost
buoyancy engine are currently being explored.
ACKNOWLEDGMENT
This work would not have been achieved without the
dedication and commitment of many personnel from NOAA
Research and our Cooperative Institute, the University of
Washington Joint Institute for the Study of Atmosphere and
Ocean. From the drawing board to the field; these successful
field missions are made possible through dedicated
administration, engineers, technicians, researchers,
communications teams, private partnerships, and the officers
and crews of the NOAA Ship Oscar Dyson and the USCG
Cutter Healy. This is Contribution No. EcoFOCI-0908 to
EcoFOCI, 2018-0166 to JISAO, and 4823 to PMEL.
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