investigations into the biology and biogeochemistry of a rapidly changing arctic ocean kevin r....

Investigations into the biology and biogeochemistry of a rapidly

changing Arctic Ocean

Kevin R. Arrigo

Department of Environmental Earth System ScienceStanford University

Background

• Circulation influenced by both Atlantic and Pacific waters

• Atlantic (red): Warm, salty, low nutrient, deep

• Pacific (blue): Cold, fresh, high nutrient, shallow

• Cold halocline layer restricts influx of nutrients from depth

Background

• Extensive continental shelves (53% of area)

- Highly productive

• Large input of fresh-water from rivers

• Relatively low surface water nutrients

• High nutrients in deep basins

Bathymetry (m)

Background

• Sea ice dynamics are important

Maximum ice extent Minimum ice extent

Background

• Sea ice dynamics are important

• Decreasing trend in summer minimum ice cover

~20% drop

Changes in Arctic Sea Ice Cover

Summer minimum sea ice cover dropped dramatically in 2007 and 2008

20082007

Changes in Arctic Sea Ice Cover

• Large area of Arctic Ocean was exposed for first timeApproximately 1.3 x 106 km2 (area in red)

• New ice-free pelagic habitat

20072006 Difference (2006-2007)

Arrigo et al. (GRL, 2008)

Given ongoing changes in Given ongoing changes in the Arctic Ocean…the Arctic Ocean…

How has primary production How has primary production changed in recent years?changed in recent years?

Background

How primary production was calculated

• Algorithm modified from Southern Ocean (Arrigo et al. 2008, Pabi et al. 2008)

• Based on remotely sensed SST, Chl a, and sea ice

• Forced with winds, cloud cover, and solar radiation

Background

• 356-459 Tg C yr-1 from 1998-2006

(Pabi et al. 2008)

• Non-significant increase in annual primary production

• 1998 within 10% of Sakshaug (2003): 329 Tg C yr-1

Pabi et al. (JGR, 2008)

• How did primary production in the Arctic vary prior to 2007?

Changes in Arctic Productivity

How has Arctic primary production changed since 2006?

2006 2007 2008 Annual Primary 459 Tg C 544 Tg C 480 Tg C Production

• 2007 and 2008 are the most productive years on record

• Between 2006 and 2007, production increased by >15%

• Only 30% of this increase was due to increased open water habitat in 2007 (Arrigo et al., GRL 2008)


• 70% of 2007 increase in primary production related to longer growing season

Spatial Changes in Arctic Productivity

Annual productionMean 2006-08(Tg C yr-1)

Largest increaseIn 2007-2008:

Beaufort, Chukchi,East Siberian, Laptev(25-75%)

23233636

4141

4848

136136127127

2626 6363

Temporal Changes in Arctic Productivity

These 4 sectors also exhibited the largest interannual differences in the timing of the spring bloom over the last 3 years

39 days27 days

48 days26 days

Temporal Changes in Arctic Productivity

Related to changes in the timing of increase in open water area

How will organisms respond to changes in the timing of the spring bloom?

21 days 31 days

40 days28 days


• Annual primary production increased by 140 Tg C yr-1

between 1998 and 2008 (statistically significant trend)

• A 40% increase over the last decade

• Unexpected given presumed nutrient limitation

• Largest increases on continental shelf

• Is this sustainable? Nutrient source?

Investigations of Climate and Environmental Change on Arctic Pacific Shelves (ICECAPS)

Where?

Beaufort/Chukchi SeaContinental shelfCanada Basin

When?

Spring/Summer 2010 & 201130-45 day cruises

Depending on ship used (Healy or Amundsen)Depending on science priorities


Who?

NASA Ocean Biol. and Biogeochem.NASA Cryosphere programPossibly NSF and Canadians

How much?

NASA OBB: 5-12 awards, ~$2 million/yrNASA Cryosphere program: 1-2 awards, ~$500K/yr


Central science question:

What is the impact of climate change (natural and anthropogenic) on the biogeochemistry and ecology of the Chukchi and Beaufort seas?


Related issues and example questions:

A. Characterize and quantify the interactions and feedbacks of water and sea ice photobiology and photochemistry with above-water, in-water, and ice radiation fields and their effect on ocean and sea ice biology, ecology, and biogeochemistry.

Example questions include:

• What impact does changing atmospheric composition (e.g., clouds, aerosols) and surface albedo have on PAR and UV radiation, and how does this influence ocean productivity and biogeochemistry?





• What are the (seasonal) relationships between algal and bacterial metabolism with above-water, in-water, and ice radiation fields (apparent and inherent optical properties)?





• What are the pathways of optically active dissolved organic matter in land, water, and sea ice, as detailed by optical and chemical observations, and their effect on land, sea, and sea ice biogeochemical interactions?





• What is the distribution, community composition and activity of microbial communities associated with the biologically-mediated, climate-related exchange processes between the Arctic Ocean, cryosphere, and atmosphere?





• How do changing sea ice conditions and radiation impact changes in biological oceanography (e.g., phytoplankton, zooplankton, fisheries) and biogeochemistry, such as changes in emissions of radiatively active gases?



B. Understanding the mechanisms controlling the fluxes of CO2, CH4, DMS, and other radiatively or biologically important gases, under different sea ice conditions, surfactants, meteorological conditions, and upper ocean turbulence regimes.


• What will be the effect of a change in the strength of the biological pump due to sea ice, land, and ocean interactions (e.g., nutrients, dissolved inorganic carbon, DIC) on the air-sea flux of CO2?





• How are gas fluxes affected by the radiation field, sea ice and riverine input, first year vs. multi-year sea ice fields, cycling of DOM and CDOM, changes in emperature, DIC and alkalinity, permafrost thawing, and other land-sea interactions?





• How do the in-water, air-sea, and through-ice biogenic fluxes of CO2, CH4, and other climatically relevant gases compare under varying sea ice radiation fields?

Cruise Track

Will depend on what proposals are funded

Will sample both open water and sea ice


Core measurements:

HydrographyVertical profiling by CTDVertical profiling by XBT, XCTDSalinity, alkalinity, dissolved oxygen, and inorganic nutrients

PhytoplanktonPhytoplankton pigments (Horn Point)Biomass (POC, PON, cell size, cell number)14C Primary Productivity


Data Synthesis, Assimilation, and Modeling:

• NASA seeks focused, multi-scale data assimilation experiments and model/forecast validation studies in the Chukchi and Beaufort Seas study area that include sea ice, ocean, atmosphere, and ecological components


Data Policy:

• All data collected will be subject to the standard NASA Earth Science data policy (http://nasascience.nasa.gov/earth-science/earth-science-data-centers/data-and-information-policy/).

• Data collected are required to be submitted to the NASA SeaBASS archive within one year of collection.

Proposal Due Date

• June 1, 2009

investigations into the biology and biogeochemistry of a rapidly changing arctic ocean kevin r....

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