The western Arctic physical climate is rapidly changing. The summer minimum sea ice extent in 2007 and 2008 covered an area which was 37% 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 30 years. As sea temperature, oceanographic currents, and prey availability are altered by this climate change, changes in baleen whale species composition 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. This combination of increasing anthropogenic impacts coupled with the steadily increasing abundance and related seasonal range expansion by the bowhead, gray, humpback, and fin whales, 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 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. The study will have four component projects: oceanography, passive acoustics, zooplankton, and climate modeling. Passive acoustic moorings, deployed concurrently with bio-physical moorings, will provide previously unattainable year-round assessment of the seasonal occurrence of bowhead, humpback, right, fin, gray, and other whales in this planning area and their response to environmental changes (including oceanographic conditions, climate, indices of potential prey density, and anthropogenic activities).
Issues & Justification
Current leasing schedules indicate that further leasing for oil and gas development is proposed for the Chukchi Sea Planning Areas. Baleen whale species including bowhead, gray, humpback, fin, right, and minke whales may occur in these areas. Timing and location of whale migrations may play 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 strategic stocks (including the endangered bowhead, right, fin, and humpback whales). Given the expected link between the spatio-temporal distribution of these species and changes in environmental variables such as oceanographic currents, sea temperature, sea ice cover, and prey availability, it is necessary to assess the spatio-temporal trends in these variables as well.
The study will have four component projects: oceanography, passive acoustics, zooplankton, and climate modeling. Passive acoustic moorings, deployed concurrently with bio-physical moorings will provide previously unattainable year-round assessment of the seasonal occurrence of bowhead, humpback, right, fin, gray, and other whales in this planning area and their response to environmental changes (including oceanographic conditions, climate, indices of potential prey density, and anthropogenic activities). This research plan therefore addresses all three major research themes of the Science Plan.
Information and annual reports from this study will be used in the preparation of draft and final environmental assessments for Chukchi Sea Lease Sales. The information will be integral to documents related to Endagnered Speciea Act (ESA), Section 7 Consultation. Study information will be used in writing post-lease environmental impact statements (EIS’s) and environmental assessments (EA’s) and in reviewing oil-industry plans for exploration, development, and transportation.
- Assess the year-round seasonal occurrence of bowhead, gray, and other whale calls in the Chukchi Sea.
- Estimate relative abundance of bowhead, gray, and other whales in the Chukchi Sea.
- 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.
- 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.
- Rerun the National Center for Atmospheric Research (NCAR) climate model (Community Climate System Model: CCSM) for future projections using the sea ice extents from 2007-08 as initial conditions.
- Analyze multiple ensemble members from the NCAR model and other International Panel on Climate Change (IPCC) models to assess the future variability of sea ice cover and extended sea ice free seasons during fall for the Chukchi Sea.
- 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.
- Provide long-term estimates of habitat use for large whale species and compare this with predictions about annual ice coverage in order to establish predictive variables to describe large whale occurrence.
This study requires deployment of a variety of instrumentation in the Chukchi Sea Planning area for year-round monitoring. This instrumentation includes three passive acoustic recorder arrays to track and monitor baleen whales and various sensors to measure chemical and physical processes in the oceanic environment. The study area encompasses approximately the area within 68°N–72°N and 157°W–168°W. The project overall is running for three field seasons (2010-12), with 2 years dedicated to analysis. Field work in all three field seasons will be conducted in late August to late September.
The passive acoustic arrays will be composed of five AURAL arranged pentagonally with ~2 miles separation between moorings. The recorders will run year-round on a duty cycle of 1.583h on every 5h, at a sampling rate of 16 kHz. This duty cycle will advance the recording period 1h/day, so that all time periods will be sampled equally. Pingers placed on the moorings will provide the calibration signals needed for calculating localization errors.
The biophysical moorings will be deployed at the center of each acoustic array and will consist of an upward looking ADCP and instruments that measure fluorescence, temperature, oxygen, ice thickness, nitrate, and salinity. At the middle array site there will also be a TAPS-8 instrument which acoustically measures zooplankton biovolume as a function of size. Furthermore, hydrographic data (temperature, conductivity, nutrients, chlorophyll, and oxygen) and zooplankton (using either double-oblique tows of paired bongo frames for depth-integrated sampling or a Tucker sled for depth stratified sampling) will be collected at the mooring sites and along eight transect lines.
While vessel is underway during daylight hours a visual survey will be conducted. Two observers will use 25x Big-Eye binoculars to call out sightings, and the data recorder will have 7x50 hand-held binoculars to identify animals close to the vessel. If a species of interest is located, the observers will collect as much information as they can on their current course and will only divert from track at the discretion of the Chief Scientist. While on station a small boat may be launched for biopsy and photo-identification purposes if time permits. There will also be a seabird observer (USF&W) onboard.
There will also be passive acoustic monitoring of marine mammals using directional sonobuoys. Once whale calls are detected a second sonobuoy can be deployed and a more accurate cross bearing location of the calling whale can be obtained. If time permits, the vessel can be diverted to that location.
In addition to the field efforts a climate model and a cumulative noise model will also be developed. The climate model will be developed by PMEL by first running the NCR CCSM model under different conditions to examine the influence of natural variability on sea ice loss, then by examining a new set of IPCC model results.
The noise model will be developed by Cornell University’s Bioacoustics Research Program using existing and newly developed analytical methods to quantify the contributions of anthropogenic sounds to the ocean noise budget.