Yvette H. Spitz Oregon State University, CEOAS Carin J. Ashjian (1), Robert G. Campbell (2), Michael Steele (3) and Jinlun Zhang (3) (1) Woods Hole Oceanographic Institution (2) University of Rhode Island, GSO (3) University of Washington Applied Physics Laboratory Western Arctic Ocean Primary Productivity Changes over the Last Three Decades and in the Future: not a Simple Story.

Ice Extent (Sept 1979) Ice Extent (Sept 2011)

NSIDC Courtesy Irina Overseem, University of Colorado Boulder. Open Water Days in the Beaufort Sea, 1980 to 2009

Deepening of the nutricline and chlorophyll maximum in the Canada Basin interior, 2003– 2009 (Fiona A. McLaughlin and Eddy C. Carmack) Salinity Depth of 33.1 salinity

How will this large scale ice melting and changes of water properties (light, temperature, mixing, etc) affect the ecosystem?

BIOMAS’ Circulation Model and Grid physical open boundary conditions imposed from a global model run Parallel ocean and sea ice model (Zhang/Rothrock 2003). => Multi-category thickness and enthalpy distribution sea ice model. => POP (parallel ocean program) ocean model (Smith et al. 1992).

DOM Small Zoo (ZS) Copepods (ZL) Detritus Flagellates (PF) Diatoms (PD) NO 3 NH 4 DOM NH4 Sinking Vertical Migration Predators (ZP) Si(OH) 4 opal Schematic of BIOMAS’ Pelagic Ecosystem Model Zhang et al. (2010) – based on Nemuro

Changes in PP and plankton in the Arctic Ocean Satellite derived PP values are from Pabi et al and Arrigo et al Is the trend the same for all the Seas? Is that due to a longer growing season? If not, then why?

Arctic Regions for Analysis Purpose

Start and End of Growing Season (10% above Phytoplankton Winter Value) Beaufort Sea Chukchi Sea DiatomFlagellateChlorophyll Year Day

Change in Spring Mean Primary Productivity (01-06) – (88-00) (07-11) – (88-00) Integrated PP (mg C m -2 d -1 ) April – June, PP and its increase over the years are small in the spring

Change of mean PAR (%) at the water surface (01-06) – (88-00) (07-11) – (88-00) PAR (W m -2 ) – April-June Spring Mean PAR

Trend of Yearly Maximum (day (black), magnitude (red)) for the Beaufort Sea

Maximum of Biomass and Primary Productivity, and Minimum of Nitrate – Change in Day from 1988 to 2010 Change in timing of the secondary producer biomass is largest in deep basin, especially for the predatory zooplankton Nitrate minimum happens earlier at the surface but later at depth in the Beaufort Sea and Deep Basin Change in timing of max. PP is the largest in the Chukchi Sea and the largest change in timing of phytoplankton happens in the Beaufort Sea

Maximum of Biomass and Primary Productivity, and Minimum of Nitrate – Change in value from 1988 to 2010 Change in the secondary producer biomass is the largest in deep basin Nitrate is decreasing at the surface (except in the Chukchi Sea) and over the first 100m Change in flagellate biomass and PP is the largest in the deep basin. Decrease of diatom biomass in Beaufort and Deep Basin

Summer Mean Int. Primary Productivity (100m or bottom) (01-06) – (88-00) (07-11) – (88-00) Integrated PP (mg C m -2 d -1 ) July – September, Decrease significantly in the Beaufort Gyre Increase on the shelves (almost double on the western Chukchi Sea shelf

Change of mean PAR (%) at the water surface (01-06) – (88-00) (07-11) – (88-00) PAR (W m -2 ) – July-September Summer Mean PAR Significant especially in the Beaufort Sea

Summer Mean Int. Total Nitrogen (100m or bottom) (01-06) – (88-00) (07-11) – (88-00) Int. Total Nitrogen (mmol N m -3 ) July – September, Decrease significantly in the Beaufort Gyre (close to be depleted at the center of the Gyre) Increase on the shelves (almost triple on the western Chukchi Sea shelf

Summer Mean Int. Chlorophyll (100m or bottom) (01-06) – (88-00) (07-11) – (88-00) Int. Chlorophyll (mg Chl m -3 ) July – September, Decrease significantly in the Beaufort Gyre (almost zero at the center Increase on the shelves (almost double on the western Chukchi Sea shelf

Summer Mean Int. Zooplankton (100m or bottom) (01-06) – (88-00) (07-11) – (88-00) Int. Zooplankton (mmol N m -3 ) July – September, Decrease in the Beaufort Gyre Increase on the shelves, especially on shelf break/slope

Summer Mean Int. Kinetic Energy (100m or bottom) (01-06) – (88-00) (07-11) – (88-00) Int. Kinetic Energy (cm 2 s -2 ) July – September, Reduction of KE on the shelves Acceleration of the Beaufort Gyre Note the change at the Bering Strait

Conclusions and future research While we found that the maximum of productivity occurs earlier and reaches higher values in general, we did not find a significant trend in the start and end of the growing season. But The timing, magnitude and pattern of cycles are changing differently from region to region. Flagellate increase is larger than diatom increase in general. Grazer increase is larger in the Deep Basin. There is increase of primary productivity and total nitrogen over the shelves (especially Western Chukchi Sea) and shelfbreak but decrease at the center of the Beaufort Gyre. This decrease of nitrate is accompanied of a reduction of primary productivity. On the edge of the gyre, there seems to be an increase of plankton biomass and primary prodiuctivity. While trends can be found, the complex nature of the Arctic Seas call for cautions when analyzing observations. High resolution models are needed to resolve the present and future changes in the Western Arctic

Surface Chlorophyll-a (mg Chl m -3 ) – July 04 - ICESCAPE Constant Chl:N Chl:N from ICESCAPE regression of Chl and PON