The Arctic Nearshore Environment:

1
The Arctic Nearshore Environment A System
Defined by Complex Hydrological and
Biogeochemical Linkages and Feedbacks
Ken Dunton The University of Texas at
Texas Marine Science Institute
2

• The nearshore zone of the Arctic Ocean has been
  largely ignored, with a few exceptions (e.g.
  Swedish Tundra Expeditions). In the U.S., little
  research effort since the end of OCSEAP funded
  studies over two decades ago.
• The region represents a dynamic boundary between
  arctic coastal plain watersheds and the arctic
  shelf that is dominated by distinctive physical
  processes that are unique to the Arctic.

3
The nearshore zone is the site of

• Most human activity, especially subsistence
  hunting
• Increased coastal erosion

Bowhead, Pt. Barrow (from D. Schell)
Camden Bay, July 1991
4

• Intense petroleum and industrial development,
  both onshore and offshore

Prudhoe Bay
Tern Island, Stefannson Sound, early July
TAPS, south of Prudhoe Bay
5

• Organic and inorganic input of materials from
  river discharge
• Substantial variations in seasonal ice-retreat
  and freshwater inputs from rivers and coastal
  runoff
• Physical extremes of temperature, winds, and ice
  cover

Ice break-up, near Cross Island, early July
6

• Migrations of anadromous fishes, migratory water
  fowl, and large animals.

Black Brant, Prudhoe Bay
S.R. Johnson, 2000
P.C. Craig, 1980
Caribou, Camden Bay
7

• Consequently, the diversity and distribution of
  nearshore marine and terrestrial organisms is
  largely governed by the physical events that
  regulate the intensity of biogeochemical and
  hydrological cycling between marine and
  terrestrial ecosystems.

Canning River, Arctic National Wildlife Refuge
8
The absence of recent studies on the arctic
nearshore zone is largely a result of

• Extremely variable and unpredictable physical and
  climatic conditions
• High costs of performing arctic field research
• The absence of logistical support and
  infrastructure to support arctic coastal studies
• Access to ice-strengthened and shallow draft
  research vessels
• Emphasis on shelf and basin research

9
Overarching goal of an Arctic Nearshore Processes
Initiative

• To improve our understanding of the
  biogeochemical and hydrological processes that
  occur on the nearshore zone of the arctic shelf
  and coastal plain with respect to changes in
  global climate with a focus on
• The lateral exchanges of carbon, nutrients,
  water, and other materials at the nearshore
  interface.
• The physical processes that regulate these
  exchanges on temporal and spatial scales.

10
Lateral exchanges coastal erosion and river
inflow

• Sediment contribution from coastal erosion can
  equal (Laptev Sea) or exceed riverine input by
  sevenfold (Beaufort Sea, Alaska).
• Rates of coastal erosion can vary considerably
  (average 1-4 m yr-1) but rates up to 18 m yr-1
  have been documented (Reimnitz et al., 1988).
• Carbon content of transported sediments varies
  from 1-6 (marsh sediments) to 15-30 (peat
  lenses).

Camden Bay, 1991
11
Productivity and Biogeochemical Cycling (carbon)

• Earlier studies demonstrated that peat carbon is
  not utilized by marine consumers and does not
  enter nearshore food webs. However, tremendous
  amounts of carbon enters the nearshore coastal
  zone from runoff and erosion. What is the fate of
  this material?

Peat on Camden Bay shoreline
From D. Schell. unpub.
D..M. Schell et al, 1982
12
Productivity and Biogeochemical Cycling (nitrogen)

• Nearshore sediments appear
• to constitute an important
• source of marine denitrification
• and loss of contained nitrogen
• for arctic waters.

• Does the decomposition of
• organic matter from coastal
• watersheds contribute a
• significant source of new
• nitrogen for nearshore primary
• producers, as reflected in late
• spring phytoplankton blooms?
  

Devol et al., 1997
13
Productivity and Biogeochemical Cycling

• The temporal and spatial scales of primary
  productivity along the nearshore arctic coast
  appear to be related to hot spots of secondary
  productivity, local hydrology, and
  nearshore/shelf circulation.

D..M. Schell et al, 1982
14
Time series of mean daily discharge
Time series for May-June 2000 of a) mean daily
discharge from the Sagavanirktok River, b) ice
thickness (solid line) and transmissivity (dashed
line). The oceanographic data are from
Stefansson Sound near Dinkham Sands.
T.J. Weingartner S.R. Okkonen, 2001
15
Light attenuation on the nearshore shelf
Light attenuation across the nearshore region of
the Mackenzie shelf in September 1986.
E.C. Carmack et. al, 1989
16
Biogeochemical linkages and feedbacks as a
function of climate change on the nearshore shelf
Vörösmarty et al., 2001 NSF-ARCSS Hydrology
Workshop Report
17
Effects of Coastal Climate change on Nearshore
Circulation and Open Water

• Some of the factors known to have significant
  impacts on nearshore processes, which are not
  well understood, include

• Timing of the breakup of the nearshore fast ice
  and the duration and magnitude of fresh water
  discharge.

• Sediment transport by fast ice

J.C. Truett, 1980
Strudel scour formation during flooding of the
fast ice, north of Sag River Delta, Stefannson
Sound
Stefannson Sound
18
Domains of the nearshore shelf can shift in
response to the magnitude and timing of
freshwater inflow events
R.W. MacDonald E.C. Carmack, 1991
B.J. Gallaway and R.G. Fechhelm, 2000
R.W. MacDonald et.al., 1987
19
Seasonal variability in domains as reflected by
vertical salinity profiles
R.W. MacDonald E.C. Carmack, 1991
Sections of salinity on the sampling transect for
(a) 6-8 September 1986, (b) 1-5 April 1987, and
(d) 25 May 1987.
20

• Nearshore circulation patterns in the Arctic are
  poorly understood how do frequent changes in
  wind direction and speed influence circulation
  and the advection of nutrients into the nearshore
  zone?

• Wind direction and speed are known to influence
  the dispersion of fast ice, rates of primary
  production, and the distribution of nekton.

J.C. Truett, 1980
Catch-per-unit effort of arctic cisco in the
Colville River as a function of average
east/west wind component (B.J. Gallaway and R.G.
Fechhelm, 2000).
21
Climate change and environmental variability

• Configuration and changes in emergent land forms
  (barrier islands) which alter the effects of wind
  on biota, water, ice movement, and exchange
  processes.

S.R. Johnson, 2000
22
Climatic forcing of coastal change
Manson et al., 2001
23
Summary

• The arctic nearshore is an ice dominated
  transition zone characterized by the complex
  exchange of water, nutrients, and organic matter
  between marine and terrestrial ecosystems.
• The lateral transfers of carbon and nutrients
  appear to play an important role in regulating
  the seasonal productivity of the nearshore zone,
  but the processes that control these transfers
  are poorly understood.
• In arctic nearshore environments, the iterative
  effect of climate change will produce a
  synergistic outcome of accelerated coastal
  erosion that will have measurable effects on
  human society, as well as have significant
  impacts on the structure and function of the
  coastal ecosystem.