Ryan R. Rykaczewski - OSU Hatfield Marine Science Center Cooperative Institute for Marine Resources Studies - NOAA Geop

Changes in source-water properties of the California Current in response to large-scale climate processes Ryan R. Rykaczewski - OSU Hatfield Marine Science Center Cooperative Institute for Marine Resources Studies - NOAA Geophysical Fluid Dynamics Laboratory Ryan.Rykaczewski@noaa.gov With ample advice from John Dunne, Charlie Stock, Nick Bond, Anand Gnanadesikan, and Bill Peterson

Outline • I. Purpose: • To understand some of the long-term climate factors which may alter the productivity of the coastal marine ecosystem. • II. Background: • What makes the marine ecosystem of the Pacific Northwest extremely productive? • III. Methodology: • Analysis of output from a global earth-system model. • IV. Discussion and implications • V. Conclusions and future directions

What makes the marine ecosystem of the Pacific Northwest extremely productive? The marine ecosystem is incredibly rich and productive, supporting fisheries (commercial and recreational) and a diversity of migratory species in summer (whales, tuna, and seabirds). What will happen to this system over the next 100 years as climate changes? What makes this such a special region of the ocean in the first place?

What makes the marine ecosystem of the Pacific Northwest extremely productive? Upwelling of cold, nutrient-rich water is the primary reason for this high productivity. This upwelling is a result of north winds in summer. alongshore, equatorward winds offshore transport upwelling

How might this upwelling of nutrients change in the future? Local conditions may change and affect the upwelling process at the coast. Possibilities: alongshore winds, alongshore currents, stratification and mixing of the water column, riverine input, atmospheric deposition ?

How might this upwelling of nutrients change in the future? Local conditions may change and affect the upwelling process at the coast. Possibilities: alongshore winds, alongshore currents, stratification and mixing of the water column, riverine input, atmospheric deposition ? ? ? ? ? ? But there could also be remote changes in the properties of the deep source waters which feed the upwelling system.

Methodology: NOAA Earth System Modeling

Methodology: NOAA Earth System Modeling Atmosphere, ocean, land, and ice components with interactive biogeochemistry. 2o x 2.5o atm. resolution; 1o x 1o ocean resolution. Ocean includes major nutrient cycles (N, P, Si and Fe) and three phytoplankton classes. Dunne, et al. (Global Biogeochem. Cycles 2005, 2007)

Global climate, pre-industrial through year 2300 IPCC Emissions Scenario A2: pre-industrial historical SRES A2 Prescribed CO2 concentration Global average surface temperature (+2.9 oC from 2000 to 2100) What are the implications of such changes for ecosystem properties in the California Current and the coastal waters of the Pacific Northwest?

Temperature increases across the basin The magnitude of the upper-ocean temperature change varies, but the direction of the change is uniform: the whole Pacific becomes warmer at the surface.

Zonal winds weaken and shift poleward, alongshore winds show little change The magnitude of alongshore winds does not change significantly.

Winter mixed-layer depth shoals Projected responses include a shallower mixed-layer depth, warmer surface layer, and little change in winds. Given the historical record, we might expect decreased nutrient supply and reduced production.

However, NO3 changes are counterintuitive… 35% decrease in the average nitrate concentration in the North Pacific (20° N to 65° N). 85% increase in average nitrogen concentration between 2000 and 2100 along the US West Coast.

How might this upwelling of nutrients change in the future? Local conditions vary in the 21st century, but not in a consistent manner that can explain the long-term increase in nitrate supply. Rule out: alongshore winds, alongshore currents, stratification and mixing of the water column, riverine input, atmospheric deposition ? ? ? ? ? ? Changes in the properties of these deep source waters appear to be more important.

Processes influencing deep water nutrients What makes deep cold waters nutrient rich? Photosynthesis Respiration

Processes influencing deep water nutrients Nutrients are depleted by photosynthesis in the surface, sunlit layer. Photosynthesis Consumed: CO2 and nutrients Released: O2 Respiration

Old, deep waters are nutrient rich Nutrients are depleted by photosynthesis in the surface, sunlit layer. Biological respiration (microzooplankton and bacteria) remineralize these nutrients in the deeper, colder layer of the ocean. Photosynthesis Consumed: CO2 and nutrients Released: O2 Respiration Consumed: O2 Released: CO2 and nutrients

Old, deep waters are nutrient rich Over time, phytoplankton continue to sink out of the surface layer to depth. At depth, nutrients and CO2 accumulate while O2 is depleted. Photosynthesis Consumed: CO2, nutrients Released: O2 time Respiration Consumed: O2 Released: CO2, nutrients

Old, deep waters are nutrient rich Over time, phytoplankton continue to sink out of the surface layer to depth. At depth, nutrients and CO2 accumulate while O2 is depleted. Photosynthesis Consumed: CO2, nutrients Released: O2 time Respiration Consumed: O2 Released: CO2, nutrients nutrients CO2

Old, deep waters are nutrient rich Over time, phytoplankton continue to sink out of the surface layer to depth. At depth, nutrients and CO2 accumulate while O2 is depleted. Photosynthesis Consumed: CO2, nutrients Released: O2 time Respiration Consumed: O2 Released: CO2, nutrients nutrients nutrients CO2 CO2

Old, deep waters are nutrient rich Over time, phytoplankton continue to sink out of the surface layer to depth. At depth, nutrients and CO2 accumulate while O2 is depleted. Photosynthesis Consumed: CO2, nutrients Released: O2 time Respiration nutrients Consumed: O2 Released: CO2, nutrients nutrients nutrients CO2 CO2 CO2

Old, deep waters are nutrient rich Over time, phytoplankton continue to sink out of the surface layer to depth. At depth, nutrients and CO2 accumulate while O2 is depleted. Photosynthesis Consumed: CO2, nutrients Released: O2 time nutrients Respiration nutrients Consumed: O2 Released: CO2, nutrients nutrients CO2 nutrients CO2 CO2 CO2

Old, deep waters are depleted of O2 Over time, phytoplankton continue to sink out of the surface layer to depth. At depth, nutrients and CO2 accumulate while O2 is depleted. Photosynthesis Consumed: CO2, nutrients Released: O2 time Respiration O2 O2 O2 Consumed: O2 Released: CO2, nutrients O2

Old means high nutrients, low O2, low pH This “age clock” continues to run as long as this water mass remains out of contact with the ocean surface and sunlight.

Old means high nutrients, low O2, low pH This “age clock” continues to run as long as this water mass remains out of contact with the ocean surface and sunlight. Photosynthesis Consumed: CO2, nutrients Released: O2 time nutrients Respiration Consumed: O2 Released: CO2, nutrients CO2 O2

Old means high nutrients, low O2, low pH This “age clock” continues to run as long as this water mass remains out of contact with the ocean surface and sunlight. The clock is “reset” if/when the water mass is mixed to the surface. Photosynthesis Consumed: CO2, nutrients Released: O2 time nutrients Respiration Consumed: O2 Released: CO2, nutrients CO2 O2

Old means high nutrients, low O2, low pH This “age clock” continues to run as long as this water mass remains out of contact with the ocean surface and sunlight. The clock is “reset” if/when the water mass is mixed to the surface. Photosynthesis Consumed: CO2, nutrients Released: O2 DEEP MIXING EVENT! time nutrients Respiration Consumed: O2 Released: CO2, nutrients CO2 O2 Age reset to 0.

Old means high nutrients, low O2, low pH This “age clock” continues to run as long as this water mass remains out of contact with the ocean surface and sunlight. The clock is “reset” if/when the water mass is mixed to the surface. O2 Photosynthesis Consumed: CO2, nutrients Released: O2 CO2 time nutrients Respiration Consumed: O2 Released: CO2, nutrients CO2 O2 Age reset to 0.

Old means high nutrients, low O2, low pH This “age clock” continues to run as long as this water mass remains out of contact with the ocean surface and sunlight. The clock is “reset” if/when the water mass is mixed to the surface. O2 Photosynthesis Consumed: CO2, nutrients Released: O2 CO2 time time O2 nutrients Respiration Consumed: O2 Released: CO2, nutrients CO2 O2 nutrients Age reset to 0. CO2

Warming reduces mixing across the basin

Current formation of source waters Deep waters which feed the coastal currents of the Pacific Northwest originate near about 150O W, or about 1000 miles offshore in the Central Pacific. These deep waters eventually upwell at the coast, rich with nutrients. 150O W current time nutrients nutrients CO2 CO2

Future formation of source waters Warmer sea-surface temperatures associated with global warming increase stratification across the entire Pacific. Local mixing in the waters of the Pacific Northwest decreases, but the mixing over the central and western North Pacific decreases as well. The initial location of the deep waters which feed the Pacific Northwest shift westward. 180O Year 2100 time nutrients nutrients nutrients nutrients CO2 CO2 CO2 CO2

Genesis of California Current waters 200-m PNW σθ ≈ 26.0 (±0.04) 200-m PNW σθ ≈ 25.7 (±0.04)

Source waters increase in age and NO3 younger older The area in which the PNW source waters are formed is projected to move west. Deep waters which enrich the coast are projected to increase in age. Nutrient content of the waters increases.

Nutrient concentration increases with increased stratification What about the other properties associate with changes in age of the water mass? 85% increase in average nitrogen concentration between 2000 and 2100 along the US West Coast.

Dissolved O2 decline is exacerbated near the coast

pH decline is exacerbated near the coast pH declines everywhere with increased atmospheric CO2. While pH is expected to decline but 0.25-0.35 elsewhere, the acidification is intensified near the US West Coast.

General results Three important lessons for the coastal ocean of the Pacific Northwest 1. Historic modes of interannual and decadal variability are likely to persist in the future, but anthropogenically forced trends may be more influential than the shorter-term oscillations. 2. Long-term relationships may be counterintuitive (and even opposite those observed at interannual to decadal time scales). Remote atmospheric changes will affect the source waters supplied to the region and need to be considered. 3. The effects of global climate changes may be exacerbated at the regional level. Nutrient supply may increase as the Pacific becomes more stratified. However, this comes at the price of dissolved oxygen and pH levels.

Future directions Three major long-term goals arising from this work: 1. Ecosystem models now are focused on either the “regional scale” or on the global scale, without much communication between the two. This work emphasizes the importance of considering the global scale influence in future studies of regional changes. 2. How do these projected changes at the base of the food web affect higher trophic levels? More complex ecosystem models need to be included in current biogeochemistry models. 3. Can this information be used to enhance the predictability and observation of hypoxic and low-pH events? Can we devise an observational system that can recognize changes in source-water properties while the water mass is 100s or 1000s of miles offshore?

The END. contact me: Ryan.rykaczewski@noaa.gov

Ryan R. Rykaczewski - OSU Hatfield Marine Science Center Cooperative Institute for Marine Resources Studies - NOAA Geop