Ocean processes affecting ice-cover in the Arctic, and their impact on

hydrocarbon exploration

William CrawfordEddy Carmack

Josef Cherniawsky

Institute of Ocean SciencesFisheries and Oceans Canada, Pacific Region

Funded by

Panel for Energy Research & Development

&

Fisheries and Oceans Canada

Project aims to evaluate the use of satellite altimetry to determine sea levels and surface currents for application

to Beaufort Sea ice cover for oil & gas industry.

Bering Strait

Aleutian Islands

Russia

USA

N. Pacific Ocean

Phase 1: Heat and fresh water transport through Bering Strait.

Fresh water flow through Bering Strait has major impact on ocean climate and ice cover in Arctic, including Beaufort Sea.

Due to Coriolis force, any northward flow through Bering Sea will tilt sea level up along US side. Southward flow tilts sea surface down.

We can determine surface flow through Bering sea by measuring sea surface slope.

Chukchi Sea

Bering Sea

TOPEX/POSEIDON9.95 -day repeat. Max lat.: 66.2 N.

ERS 35-day repeat. Max lat.: 81.5 N.

Altimeter radar signals measure both sea surface height and slope along their tracks.

T/P is accurate to about 3 to 5 cm.

Radar signals from these satellites penetrate clouds, but fail in ice-covered waters.

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We computed these tidal charts from the T/P signal directly. The tidal constants are then used to de-tide the T/P signal.

ERS signals cannot be de-tided in this manner; instead, we require tidal constants from an accurate regional model.

For now, we examine along-track T/P signals only, to determine tidal constants:Q1 O1 P1 K1 2N2 M2 N2 S2 K2

(Cherniawsky et al., 2001).

Phase 1 (Near-field): Focus on T/P lines in Bering Strait at extreme northern T/P limit.

Russia

USA

Initial results suggest that we can see significant signals in sea level anomaly (Left panel; Blue is low, Red is high.)

Typical transport is 0.5 x 106 m3s-1 to the North (+ve direction).

Transport anomaly (right panel) is computed directly from sea surface slope. It too shows significant change within some summers and from year to year.

**Sea-surface slope across Bering Strait indicates surface flow through the Strait, due to Coriolis force.

Rebecca Woodgate and Knut Aagard, University of Washington, provided data on flow speed in Bering Strait, 2 Sept 2000.

They have time series of current observations at single points in Bering Strait. In March 2003 we will combine both set of measurements to improve fresh water transport calculations.

Compare previous image of northward speeds with T/P heights in Bering Strait, Sept., 2000

Coverage of waters north of 60N by ERS-1 and 2.

Phase 2:

Use T/P, ERS-1&2 to determine summer sea level and current anomalies for Bering Sea, Beaufort Sea and Arctic Ocean.

Figures show progress to date with numerical models of ocean tides, using finite element approach with data assimilation, led by M. Foreman, IOS .

M2 (top) and K1 (bottom) are the largest of about 20 tidal constituents that we will model, to simulate and then remove tidal signals from ERS-1 and 2 signals.

Russia

Russia

USA

USA

Bering Sea

Bering Sea

These two images show examples of cross-shelf sea-surface slope, measured by T/P before and during 1997/98 El Nino. We use these measurements to determine variability in heat transport along our coast, from 1997 to 2001.

Left: Almost no slope and heat flow flow between late March and mid-May, 1997

Top: Strong slope and northward heat flow in January to February, 1998, during El Nino.

We plan to examine ERS-1 and ERS-2 observations, to determine possible applications to:

•Fresh water & heat flow through Beaufort Sea for climate & ice studies,•Storm surge studies in Beaufort Sea and at Tuk,•Warnings of strong currents at drill rigs.

Images like this are available in near-real-time from an American Web site, but do not cover oceans beyond 60N or 60S.

This Web site provides these images to the offshore production industry, who need to know if this eddy is approaching.

Currents in these eddies can impact drilling operations.

This technique might be useful in the Beaufort, using ERS and Envisat observations.

Summary:

•ERS-1 and ERS-2 observations will be improved with better tidal constants from regional tidal model, and will be examined for climate series in Chukchi and Arctic.•T/P observations show summer anomalies of flow through Bering Strait, and in Bering Sea.

We will examine three features of ERS and T/P observations:(1) Use all local measurements, and collaborate with Americans and Russians to determine Bering Strait heat and fresh-water flux.(2) Far-field study will relate flux through Bering Strait to anomalies of ice-cover in Beaufort Sea, to investigate interannual variability of ice cover.(3) Examine application of ERS to provide high-current warnings, and ground-truth data for storm surges.

Technique will be used indefinitely: •Jason series of satellites is intended to monitor global sea level rise, •Envisat, the ERS replacement, is the first of many such satellites launched and planned by the European Space Agency.