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STUDY TITLE: Chukchi Offshore Monitoring in Drilling Area (COMIDA): Factors Affecting the Distribution 

and Relative Abundance of Endangered Whales and Other Marine Mammals in the Chukchi Sea

REPORT TITLE: Final Report of the Chukchi Sea Acoustics, Oceanography, and Zooplankton Study

CONTRACT NUMBER: M09PG00016

SPONSORING OCS REGION: Alaska

APPLICABLE PLANNING AREA: Chukchi Sea

FISCAL YEARS OF PROJECT FUNDING: FY 2010-2014

COMPLETION DATE OF REPORT: August 2015

COSTS BY FY: FY 2010: $2,515,110

FY 2011: $1,519,011 

FY 2012: $1,223,782 

FY 2013: $ 801,995 

FY 2014: $ 313,330 

CUMULATIVE PROJECT COST: $6,373,228

PROJECT MANAGER: Dr. Catherine Berchok, Dr. Phillip Clapham

AFFILIATION: National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine 

Fisheries Service, National Oceanic and Atmospheric Administration

ADDRESS: 7600 Sand Point Way, NE, Seattle, WA 98115-6439

PRINCIPAL INVESTIGATOR(S)*: Catherine Berchok (NMML) PI of passive acoustic operations; 

Christopher Clark (Cornell University) PI of noise modeling and auto-detection buoy; Jessica Crance 

(NMML) Co-PI of acoustics; Sue Moore (S&T) Science advisor (ecosystems); Jeff Napp (RACE) PI of 

biological oceanography; James Overland (PMEL) Science advisor (climate); Brenda Rone (NMML) PI of 

visual surveys; Phyllis Stabeno (PMEL) PI of physical oceanography; Muyin Wang (JISAO) PI of climate 

modeling.

KEY WORDS: acoustics, passive acoustics, oceanography, zooplankton, moorings, sampling, climate, 

whale, distribution, Arctic, Alaska, Bering Sea, Chukchi Sea, Barrow

BACKGROUND: The western Arctic physical climate is rapidly changing. The summer Arctic minimum 

sea ice extent in September 2012 reached a new record of 3.61 million square kilometers, a further 16% 

reduction from a record set in 2007 (4.30 million square kilometers). This area was more than 50% less 

than that of two decades ago. The speed of these changes was unexpected, as the consensus of the 

climate research community just a few years ago was that such changes would not be seen for another 

thirty years. As sea temperature, oceanographic currents, and prey availability are altered by climate 

change, changes in baleen whale species composition, abundance, and distribution are expected (and 

evidenced already by local knowledge and opportunistic sightings). In addition, the observed northward 

retreat of the minimum extent of summer sea ice has the potential to create opportunities for the 

expansion of oil and gas-related exploration and development into previously closed seasons and 

localities in the Alaskan Arctic. It may also open maritime transportation lanes across the Arctic adding to 

the ambient noise in the environment. This combination of increasing anthropogenic impacts coupled 

with the steadily increasing abundance and related seasonal range expansion by bowhead (Balaena 

mysticetus), gray (Eschrichtius robustus), humpback (Megaptera novaeangliae), and fin whales 

(Balaenoptera physalus), indicates that more complete information on the year-round presence of large 

whales is needed in the Chukchi Sea planning area. Timing and location of whale migrations may play 
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an important role in assessing where, when, or how exploration or access to petroleum reserves may be 

conducted to mitigate or minimize the impact on protected species.

This study, known as CHAOZ, combined arrays of long-term passive acoustic recorders with 

collocated biophysical and oceanographic moorings in the Chukchi Sea. The passive acoustic arrays 

monitored year-round for the presence of baleen whales, as well as odontocetes, pinnipeds, and 

environmental and anthropogenic noise. The biophysical and oceanographic moorings recorded such 

parameters as zooplankton abundance and density, ice concentration and thickness, chlorophyll, nitrate, 

oxygen, PAR, temperature, and salinity, as well as current speed and direction. To complement these 

data and provide a more immediate assessment of whale presence, a short-term real-time auto-detection 

buoy was deployed during the summer of 2012 to monitor for bowhead whales, and transmitted data via 

satellite whenever a vocalization was detected. In addition, climate modeling was utilized to predict future 

sea ice and oceanographic conditions; results from these models were then used to predict future marine 

mammal distribution based on estimated sea ice and climate conditions. Noise modeling was also 

included to determine the current ambient noise levels in the Chukchi Sea based on anthropogenic and 

environmental sources, as well as predict increases in those levels due to sea ice retreat, increased 

shipping, or other factors. To complement and calibrate the long-term data, shipboard observations and 

measurements were collected during three fall field surveys. These included sampling stations that 

conducted CTD casts and zooplankton net tows, 24-hour passive acoustic monitoring using sonobuoys, 

opportunistic visual surveys for marine mammals, and satellite-tracked drifters.

This study had five component projects: oceanography, passive acoustics, zooplankton, climate 

modeling, and noise modeling. Passive acoustic moorings, deployed concurrently with bio-physical 

moorings, provided previously unattainable year-round assessments of the seasonal occurrence of 

bowhead, humpback, right, fin, gray, and other whales in this planning area and along with environmental 

metrics (including oceanographic conditions, climate, indices of potential prey density, and anthropogenic 

activities). Moorings permit observations during long periods when ice covers the region, especially 

during the critical spring and early summer periods when spring phytoplankton blooms occur. Such 

measurements are virtually impossible to obtain from ships, because of the relatively short duration of 

cruises and severe limitations in the availability of ships able to work in ice-covered seas.

OBJECTIVES: The overall goal of this multi-year IA study was to document the distribution and relative 

abundance of bowhead, humpback, right, fin, gray, and other whales in areas of potential seismic 

surveying, drilling, construction, and production activities and relate changes in those variables to 

oceanographic conditions, indices of potential prey density, and anthropogenic activities.

The specific objectives are:

1. Assess the year-round seasonal occurrence of bowhead, gray, and other whale calls in the 

northeastern Chukchi Sea.

2. Estimate relative abundance of these whales.

3. Obtain two full years of biophysical measurements on the shallow Chukchi shelf utilizing moorings at 

three sites, and collect hydrographic and lower trophic level data during deployment/recovery of the 

moorings.

4. Evaluate the extent to which variability in environmental conditions such as sea ice, oceanic currents, 

water temperature and salinity, and prey abundance influence whale distribution and relative 

abundance.

5. Run the National Center for Atmospheric Research (NCAR) climate model (Community Earth System 

Model: CESM1.0) for future projections using the sea ice extents from 2007/2008 as initial conditions.

6. Analyze multiple ensemble members CESM as well as the group of CMIP5 models to assess the 

future variability of sea ice cover and extended sea ice free seasons during fall for the Chukchi Sea.

7. Evaluate whether changes in seasonal sea ice extent are resulting in a northward shift of Bering Sea 

cetacean species such as fin, humpback, and North Pacific right whales.

8. Provide long-term estimates of habitat use for large whale species and compare this with predictions 

about annual ice coverage to establish predictive variables that describe large whale occurrence.

9. Develop a quantitative description of the Chukchi Sea’s noise budget, as contributed by biotic and 

abiotic sound sources, and continuous, time-varying metrics of acoustic habitat loss for a suite of 

arctic marine mammal species.
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10. Develop a near-real-time passive acoustic monitoring system that can be used as an impact 

mitigation tool.

DESCRIPTION: This study was conducted in the Bering and Chukchi Seas over the continental shelf. 

Field operations were scheduled roughly for mid-August through mid-September, although acoustic 

sampling and oceanographic moorings collected data year-round. Field projects were conducted in 2010-

2012. The primary projects included:

Moorings and oceanography – Moorings and oceanographic sampling at stations along designated 

transect lines occurred each year. Drifters were also deployed in 2011.

Passive acoustic monitoring – Moorings collected year-round data to provide information on the spatial 

and temporal distribution of marine mammals in the study area. Sonobuoys were deployed during the 

visual surveys to gather finer scale distribution data.

Visual surveys – Boat surveys were conducted each year to gather distribution data and relative 

abundance of whales in the area.

Climate Modeling – Climate models were run to investigate projections of future sea ice and ocean 

conditions in the Chukchi Sea based on coupled climate models.

Noise Modeling – Noise modeling was done to quantify and assess the Chukchi Sea’s “noise budget” 

(including biotic and abiotic sound sources).

SIGNIFICANT CONCLUSIONS: The Chukchi Sea shelf is a bathymetrically complex region where airsea-ice interactions govern ecosystem structure and function. To better understand the underlying 

mechanisms that control species distribution and abundance, one needs continuous monitoring of the 

ecosystem through all the seasons. Only through continuous observation will we have a chance at 

creating prognostic ecosystem models and conceptual frameworks to predict the impact of anthropogenic 

and natural forcing on the Arctic.

CHAOZ used a combination of autonomous moored sensors and shipboard measurements to increase

our understanding of how climate and human activities will impact Arctic marine mammal species. The 

project successfully used moored passive acoustic sensors, and physical, chemical, and biological 

sensors to provide estimates of key variables for two years, including periods of 100% ice coverage of the 

shelf waters. These sensors captured both the mean properties (e.g., areal attendance by species, 

transport, salinity, ice thickness, nutrient concentration), but also the variability in the system. We learned 

that both the mean properties and the “events” (e.g., increased beluga calls during polynya formation, 

transport up Barrow Canyon) are important to the ecosystem. We successfully used our own climate 

model, the physical, chemical, and biological understanding gained in CHAOZ, and existing information 

on the life histories of specific marine mammals to start to predict changes in species distribution, 

abundance, and feeding that may result from loss of seasonal sea ice in the Chukchi. Some of these 

predicted changes may increase the spatial overlap of the marine mammal species with the oil lease 

areas. Other predicted changes may impact subsistence hunting. Detailed results from the study are 

presented in the Final Report. 

STUDY PRODUCTS: A Final Report was produced, which included a summary of all data collected in 

2010-2012 and analyses of data. Additional products included 4 Annual Reports, 19 oral presentations, 

12 poster presentations, and 10 published/in review/in prep papers/government reports presenting data 

collected during the CHAOZ study.

*P.I.’s affiliation may be different than that listed for Project Manager(s).
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Figure 1. Map showing general study area for the CHAOZ project with CSESP study areas displayed.