Challenges• Small internal deformation scale-

dynamically wide strait.• Broad West Greenland shelf.• Ice cover & icebergs.• Freshwater moves in thin (~50 m)

surface layer.• Quantify liquid & ice contributions at

monthly to inter-annual time scales.

S

Moorings: Ice draft/velocity, absolute geostrophic velocity, low-mode u, T, S structure, marine mammals (‘06-’08)

Shelf Moorings: Low-cost (~$10k) ICECAT for T-S near ice-ocean interface, upward looking acoustic current profilers and bottom-mounted T-S.

Acoustically-navigated Gliders: Repeated sections (5 km, resolves deformation scale) at O(week) timescales between 500-m isobaths. Samples at ice-ocean interface. Temperature, salinity, dissolved oxygen (other?).

Ship-based Hydrographic Sections: Autumn. Biogeochemical tracers (nutrients, trace metals, TOC, TAlk, CFCs, oxygen isotopes. Spans broad region from S. Baffin Bay to N. Labrador Sea.

Seaglider and Sensors• Hull length: 1.8 m, Wing span: 1.0 m• Mass: 52 kg• Surface to 1000 m.

• Slow: horizontal speed 0.1 - 0.45 m/s (~22 km or 12 nm per day @0.25 m/s)

• Vertical speed 0.06 m/s (minimum)

• Endurance depends on ambient stratification, dive depth and desired speed

• Longest range to date: 3900 km

• Longest endurance to date: 31 weeks

• Sensors: SBE conductivity & tempreature, SBE43 or Aanderaa optode dissolved oxygen. Fluorometers, backscatter, ADCP may be possible.

ICECAT for shallow shelves, moorings• Samples in ice-threatened near-surface

layer.• Shallow element expendable, data logged

below.• Inexpensive (~$10k), deploy many.• 2004(1), 2005(2), 2006(4), 2007 (5)• Contributing this technology to Bering

Strait, other projects.

Operations beneath ice require acoustic navigation (RAFOS), advanced autonomy.

Acoustic data upload desirable for ‘insurance’.

First section beneath ice-covered western Davis Strait in Dec 2006… the system works, but there have also been setbacks associated with platform reliability.

IPY/AON developments include refining under-ice glider system, implementing moored ‘data depot’ for periodic data offload while operating under ice.

Ice

First Glider-based Section Under the Ice:December 2006• Fully navigated using RAFOS array.

• Fully autonomous operation- glider decided where to go, when to attempt to surface, without human intervention.

• Under-ice glider system works, but there have also been setbacks associated with platform reliability.

• Observations to within a few meters of ice-ocean interface, roughly 5 km horizontal resolution. Resolved south-flowing, surface-trapped Arctic outflow from CAA.

REMUS Operations offshore of Barrow

Pacific Water inflow is concentrated in the region between the coast and Barrow Canyon. The center of Barrow Canyon is only about 20 km offshore of Barrow, with maximum depths of about 120 m. These length scales are well suited to the capabilities of REMUS.

• Water mass transformation processes occurring on the Chukchi Shelf (mixing, cooling, and salinity changes due to ice formation and melting) modify the Pacific Water on its way to the Arctic.

• The most important transformations occur during winter, beneath sea ice, and are difficult to observe using conventional techniques.

• The inflow of modified Pacific Water is critical to maintaining the “cold halocline” in the western Arctic.

Plueddemann

The REMUS AUV

REMUS is a relatively small (8” daim x 6’ long), light (100 lb) vehicle capable of ~3.5 kt speed and ~12 hr endurance (~75 km along track) with a payload of navigation aids and oceanographic sensors.

Propulsion and steering

GPS/Iridiumantenna

MSTL 600 kHzSidescan sonar

Wet-Labs ECO-Puck Triplet

Seabird SBE- 49pumped CTD

RDI 1200 kHz ADCP, up-and down-looking

Kearfott T-16Inertial Navigation System

Long-BaseLine(LBL) trackingtransducer

Acoustic modem(operates throughLBL transducer)

Plueddemann

Cross-Shore Transects

The typical cross-shelf hydrography was best characterized by transects from the last mission on 29 August. The warm, fresh surface water (above 20 m) is the Alaskan Coastal Current, which follows the coastal topography after passing through Bering Strait. T/S characteristics below 20 m are consistent with subsurface, summer-water inflow at Bering Strait.

Four of the five transects were consistent with this relatively simple picture of coastal hydrography

Plueddemann

Gavrilov & Mikhalevsky

Acoustic Paths• TAP (blue)• ACOUS (red)• 20 Hz source• Basin-wide ranging

APLIS

ACOUSSource

Nan

sen Bas

in

Fram

Bas

in

Greenland

RussiaCanada

Spitsbergen

Basin Scale Acoustic Navigation and Communications(?)

Acoustic navigation- GPS analog, critical enabling technology.

Acoustic comms- Iridium analog, less important given decreasing seasonal ice cover?

Transmission loss along ACOUS path at 50 m and 400 m modeled for a broadband signal

0-dB SNR for a 50-Watt (~190 dB) source

Range, km200 400 600 800 1000 1200

30

40

50

60

70

80Depth: 400 m

-120

-115

-110

-100-95

-90

-140

-130

-120

-110

-100

-90

-80

-105

200 400 600 800 1000 1200

30

40

50

60

70

80-135

-130-125

-120

-115

-110

-105

-100

-95

-90

-85

Range, km

Fre

quen

cy,

Hz

Depth: 50 m

-20-dB SNR for a 50-Watt (~190 dB) source

Gavrilov & Mikhalevsky

Cabled/autonomous transceiver nodes

Cabled transceiver nodeswith shore terminals

Autonomous sources Acoustic observation paths

Cable

90E

30

150

60

120

120

60

150

30

1800

GGGrrreeeeeennnlllaaannnddd

RRRuuussssssiiiaaa

CCCaaannnaaadddaaa

4000

500

35002000

500

500

2000

3500

2000

500

ACOUSsource

90W

Notional acoustic network

Gavrilov & Mikhalevsky

1. Weight, power consumption and reliability of low-frequency sources, especially for mobile platforms

Most serious problems

3. Slow communication rate

2. Doppler effect for mobile platforms

4. Accurate timing for mobile platforms

5. Separation of acoustic thermometry/halinometry data from navigational errors.

6,7,… ?

Arctic Species of Interest: most Circumpolar & Subsistence Targets

WHALESBowheadBeluga (white)Narwhal

SEALSRinged, BeardedHarp, HoodedRibbon, Spotted

WALRUSPOLAR BEAR

Sue Moore

Frequency ranges of cetacean calls ~ hearing capability: audiograms available for few spp.

10

100

1000

10000

100000BlueFin GrayBryde's HumpbackMinkeRight (2)Pygmy rightBowheadSei Sperm whaleMonodonts (2)Beaked whales (3)Cephaloryhnchinae (2)River dolphins (3)N. Rt. whale dolphinSteninae (3)Delphininae (14)Pilot whales (2)Porpoises (3)Killer whales (2)

Frequency, Hz

Dolphins

Mysticete whales

??

?

Dave Mellinger and Sara HeimlichOregon State Univ. & NOAA/PMEL

What Should ANCHOR Participants Do?

• Investigate the need for an authorizationLetter of Authorization (LOA)Incidental Harassment Authorization (IHA)

• Specifications of Transmission will be RequiredFrequency & Amplitude (Source Level)Where, When (Duty Cycle) & Transmission LossProximity to marine mammal concentrations & to human subsistence activities (S-P-R Model)

IF low noise levels, short duty cycles & minimum spatial/temporal overlap, seek Finding of No Significant Impact, via memo with NOAA/PR

Sue Moore

Craig Lee, Jason Gobat, Beth Curry, Applied Physics Laboratory, University of WashingtonRichard Moritz, Kate StaffordBrian Petrie Bedford Institution of OceanographyMalene Simon Greenland Nature Institute

An Innovative Observational Network for Critical Arctic Gateways: Understanding Exchanges through Davis (and Fram) Strait

Buoyancy Barrier to Convection (from Bailey, Rhines & Häkkinen)

• 0-500m difference between thermal and haline components of dynamic height (blue: S, red: T)

• Transport and fresh over-capping of the subpolar gyre and Nordic Seas modulates MOC

from Dickson et al, 2005

Fluxes at major ocean gateways

• Understand partitioning between FW exchange west and east of Greenland, impacts on deep water formation and meridional overturning circulation.

• CAA/Davis Strait + Fram Strait captures nearly all of the Arctic FW discharge and primary Atlantic inflow.

Technology development for the Arctic Observing Network

• Ice-capable gliders

• New mooring technologies- ice-ocean interface, shallow shelves, light-weight through-ice (Switchyard).

• Acoustic navigation and communications.

Pacific Water Transformation

Water mass transformation processes occurring on the Chukchi Shelf (mixing, cooling, and salinity changes due to ice formation and melting) modify the Pacific Water on its way to the Arctic.

The most important transformations occur during winter, beneath sea ice, and are difficult to observe using conventional techniques.

The inflow of modified Pacific Water is critical to maintaining the “cold halocline” in the western Arctic.

[ Courtesy of T. Weingartner, U. Alaska ]