Climate-based
Assessment and
Forecasting
for
Ecosystems in the
The purpose of CAFE Gulf of Maine is to apply knowledge of long-term variability
in the Gulf of Maine to improve our Gulf
ability to manage
marine resources.
of Maine
Goals:
www.eas.cornell.edu/CAFE
1. Characterize the influence of interannual climate fluctuations on the
physical and biological environment in the Gulf of Maine.
2. Identify gaps in our knowledge
3. Develop indices/models to assess or forecast important ecosystem
processes
4. Improve the flow of information between research and management
communities
CAFE Workshop II
NOAA’s Coastal Ocean Program has provided funds to host two workshops
to help further these goals. The first workshop, held in June 2003, assembled a
diverse group of researchers and managers to discuss the current state of our
knowledge of interannual variability in the Gulf of Maine and how to better use
this knowledge in resource management. The second workshop will closely
examine the causes and consequences of a major shift in the Gulf of Maine
ecosystem during the 1990s. A major aim of the workshop will be to produce a
paper synthesizing our knowledge of the changes in the 1990s.
Invited Participants
Andrew Pershing, Cornell University
Barb Bailey, University of Illinois
Jon Brodziak ,NEFSC Woods Hole
Brad deYoung, Memorial University
Ted Durbin, URI GSO
Chuck Greene, Cornell University
Joe Green, NEFSC Narragansett
Sirpa Hakkinen, NASA Goddard
Erica Head, Bedford Institute of
Oceanography
Lew Incze, University of Southern
Maine
Jack Jossi, NEFSC Narragansett
Joe Kane, NEFSC Narragansett
**Unable to attend
Draft Agenda
Tuesday, December 14
Jason Link, NEFSC Woods Hole
Greg Lough, NEFSC Woods Hole
Bruce Monger, Cornell University
Dave Mountain, NEFSC Woods Hole
Loretta O’Brien, NEFSC Woods Hole
Bill Overholtz, NEFSC Woods Hole
Jamie Pringle**, University of New
Hampshire
Jeff Runge, University of New
Hampshire
Doug Sameoto, Bedford Institute of
Oceanography
Peter Smith**, Bedford Institute of
Oceanography
08:30—Breakfast & registration
09:00—Introduction
09:15—Presentations on patterns in specific regions and processes
Gulf of Maine
Scotian Shelf
Newfoundland Shelf
Consider physics, phytoplankton, zooplankton, fish
Dave Mountain-- salinity variability during the 90s
Doug Sameoto-- CPR trends in NW Atlantic
10:30—break
11:00—resume presentations
12:30—lunch
13:15—Discussion
Scientific issues
Are NAO and shelf salinity anomaly modes sufficient to
describe changes in the Gulf of Maine?
Can we generalize response of ecosystems to these modes?
Can we identify indicator species?
Are we seeing regime shifts?
Are we seeing natural variability or global warming?
What can we forecast? Does it matter?
Workshop Products
Synthesis paper or papers?
Project or proposal ideas?
Recommendations for further monitoring or sampling?
15:00—break
15:30—Small group discussion
17:00—adjourn
19:00—dinner
Wednesday, December 15
08:00—Breakfast
08:30—Summaries from small groups
09:30—Refocus discussion
10:00—break
10:30—Additional small group discussions
12:00—lunch
12:45—Continue work on products
14:30—Summary and future plans
15:00—adjourn
Background
The Gulf of Maine contains several important commercial fisheries, most
notably those for cod and haddock on Georges Bank and in the Gulf. Assessing
the recruitment of these species is a key part of NOAA Fisheries research in this
region. Accurate estimates of recruitment are vital to determining the abundance
of these species and for setting catch limits. The ability to forecast recruitment a
year or two in advance would allow fisheries managers to develop long-range
plans for these populations. Our research goals are directed towards developing
the knowledge and tools necessary for these predictions and focus on
understanding the influence of basin-scale climate variability on the Gulf of Maine
ecosystem.
Although the ecosystems in the Gulf of Maine are the primary focus of our
project, we recognize that processes in Gulf of Maine can be influenced by
conditions in neighboring regions. An important goal of our project is to separate
processes that are internal to the Gulf of Maine from those that are part of a
larger scale pattern. We expect that any large scale patterns should have a
stronger impact, should be more persistent, and offer a greater potential for
forecasts. To examine these patterns, we need to compare the response of
ecosystems along the Northwest Atlantic Shelf. We have identified two largescale patterns operating in the Northwest Atlantic. These patterns: the North
Atlantic Oscillation (NAO) and a shelf salinity anomaly pattern, have impacted the
Gulf of Maine during the last 20 years, and the main goal of the second workshop
is to describe the impact of these patterns.
NAO Pattern
The North Atlantic Oscillation (NAO) is the dominant climate mode over
the North Atlantic, especially during winter (Hurrell 1995). Recent studies in both
the Northeast and Northwest Atlantic have linked substantial physical and
biological variability to variations in winter conditions indicated by the NAO Index
(Fromentin and Planque 1996; Heath et al. 1999; Conversi et al. 2001;
MERCINA 2001). In the Northwest Atlantic, the NAO Index is a good indicator of
mean winter conditions over the Labrador Sea and the storm formation over
Cape Hatteras. These two centers of action bracket the Gulf of Maine, and
suggest that the NAO could strongly impact this region. Analysis of hydrographic
records from the Gulf of Maine and adjacent shelf and slope regions indicate a
strong association between the NAO and the water masses in this region
(MERCINA, 2001). When the NAO Index is negative, the transport in the
shallow, baroclinic Labrador Current increases, bringing a relatively cool, fresh
water mass known as Labrador Subarctic Slope Water (LSSW) into the region.
The alternation between LSSW and its warmer analog Atlantic Temperate Slope
Water (ATSW) occurs over a wide area, from roughly the Mid-Atlantic Bight to
the Laurentian Channel. Due to this large-scale coherent response, this region
has been dubbed the “Coupled Slope Water System” (CSWS) (MERCINA 2001).
The changes in the CSWS are strongly negatively correlated with the NAO at a
lag of one year. The presence of a significant lag makes it possible to forecast
the state of the CSWS using the previous year’s NAO Index value (Greene and
Pershing 2003). These forecasts would be an invaluable management tool if the
state of the CSWS can be linked to important ecosystem parameters.
The state of the CSWS appears to be a broad indicator of environmental
conditions in the Gulf of Maine region. Analysis of time series from NMFS’s
Continous Plankton Recorder (CPR) survey suggest a positive association
between the CSWS and the abundance of the large copepod Calanus
finamrchicus, and possibly, phytoplankton abundance. Several hypotheses may
explain these correlations. ATSW, the water mass present following positive
NAO conditions has characteristically higher concentrations of nutrients than
LSSW (Petrie and Yeats 2000). These differences may provide a “bottom-up”
explanation for the phytoplankton and zooplankton changes. While trophic
processes are likely important, work in the Northeast Atlantic suggests that shelf
populations of Calanus may be more sensitive to changes in circulation,
especially the coupling between shelf and slope regions. Calanus requires deep
water during autumn and early winter. During this period, Calanus late-stage
copepodites descend to depth (>100m) and enter a state of reduced activity
known as diapause. This overwintering strategy means that Calanus populations
in shelf regions must be reassembled each spring from populations which spent
the winter in deep water.
Although it is only a single species, Calanus dominates the biomass of the
GOM region during the late spring and early summer where it is an important link
between the primary productivity of the spring bloom and higher trophic levels. In
particular, early stages of Calanus are an important component of the diet of
larval cod and haddock (Kane 1984), while dense aggregations of later stages
are an important food resource for the endangered North Atlantic right whale
(Kenney et al. 1986; Mayo and Marx 1989; Wishner et al. 1995; Kenney 2001).
Preliminary analyses suggest that there is unlikely to be a simple linear
relationship between Calanus abundance and cod and haddock recruitment, at
least on Georges Bank. Similarly, there is no simple relationship between
Calanus and right whale reproductive success; however, a simple model which
accounts for the non-linearities inherent in the whales’ three year reproductive
cycle does suggest a significant association between Calanus and right whales
(Greene et al. 2003; Greene and Pershing 2004).
The scientific goal of the CAFÉ GoM project is to understand how largescale climate processes such as the NAO influence the physical and biological
conditions in the Gulf of Maine. This project’s management mission is to identify
a set of easily measured indices that can be used to improve the management of
commercial and endangered populations in this region. Focusing on remote
climate forcing, increases the possibility of uncovering relationships with
significant lags (>2 months).
Shelf Salinity Anomaly
Surface waters along the entire Northwest Atlantic Shelf were noticeably
fresher during the 1990s (Drinkwater et al. 2003; Mountain 2004), (Smith et al.
2001) attributed this large scale freshening to increased freshwater and ice
cover on the Labrador Shelf. Looking more closely at the Labrador Sea,
(Häkkinen 2002) found that the surface waters there, especially on the shelf
became dramatically fresher in the 1990s.
The 1990s shelf salinity anomaly was associated with changes on multiple
trophic levels in ecosystems along the entire Northwest Atlantic Shelf. In the Gulf
of Maine, we have documented a dramatic increase in the abundance of several
copepods, including Centropages typicus and Oithona spp. The increases in
these populations was most apparent during the fall and winter. The CPR color
index, a qualitative measure of phytoplankton abundance based on the
discoloration of the sampling silk, indicates higher fall-winter phytoplankton
concentrations during the 1990s. This pattern of reduced surface salinity,
increased phytoplankton abundance, and increased copepod reproduction is
consistent with the field observations made by Durbin et al. (2003). The copepod
community on the Scotian Shelf exhibited similar changes during the 1990s, and
(de Young et al. 2004) noted a similar pattern in the color index data from the
Newfoundland Shelf.
Some questions
1. What caused the surface freshening in the 1990s? Global warming?
2. Is there a uniform ecosystem response to the freshening?
3. What is the impact of these changes on higher trophic levels?
4. Can we incorporate knowledge of long-term climate and ecosystem
variability in resource management?
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