Oceanography and Atmospheric Sciences and Meteorology Commons^™

Sensitivity Of The Relationship Between Antarctic Ice Shelves And Iron Supply To Projected Changes In The Atmospheric Forcing, Michael S. Dinniman, Pierre St-Laurent, Kevin R. Arrigo, Eileen E. Hofmann, Gert L. Van Dijken

CCPO Publications

Upward advection or mixing of iron-rich deep waters due to circulation changes driven by the rate of basal ice shelf melt was shown to be a primary control on chlorophyll a production in coastal polynyas over the Antarctic continental shelf. Here, the effects of atmospheric changes projected in 2100 on this relationship were examined with a 5-km resolution ocean/sea ice/ice shelf model of the Southern Ocean with different simulated dissolved iron sources and idealized biological uptake. The atmospheric changes are added as idealized increments to the forcing. Inclusion of a poleward shift and strengthening of the winds, increased precipitation, and …

The Southern Ocean Ecosystem Affects The Entire World, Eugene J. Murphy, Nadine M. Johnston, Eileen E. Hofmann, Richard A. Phillips, Jennifer E. Jackson, Andrew J. Constable

CCPO Publications

The Southern Ocean, which flows around the Antarctic continent, is home to vast numbers of unique and remarkable animals, including penguins, albatrosses, petrels, seals, and whales. The ocean bursts into life every spring, fueling a summer feeding and breeding frenzy. During the dark winter months, there is little food and life is very harsh. Human activities such as fishing and pollution are affecting this ecosystem, as is climate change. These ecosystem changes matter beyond the Southern Ocean! Ocean currents carry nutrients and organisms into and out of the Southern Ocean. Many marine mammals and seabirds swim or fly in and …

Modeling Iron And Light Controls On The Summer Phaeocystis Antarctica Bloom In The Amundsen Sea Polynya, Hilde Oliver, Pierre St-Laurent, Robert M. Sherrell, Patricia L. Yaeger

CCPO Publications

Of all the Antarctic coastal polynyas, the Amundsen Sea Polynya is the most productive per unit area. Observations from the 2010-2011 Amundsen Sea Polynya International Research Expedition (ASPIRE) revealed that both light and iron can limit the growth of phytoplankton (Phaeocystis antarctica), but how these controls manifest over the bloom season is poorly understood, especially with respect to their climate sensitivity. Using a 1-D biogeochemical model, we examine the influence of light and iron limitation on the phytoplankton bloom and vertical carbon flux at 12 stations representing different bloom stages within the polynya. Model parameters are determined by …

Analysis Of Iron Sources In Antarctic Continental Shelf Waters, Michael S. Dinniman, Pierre St-Laurent, Kevin R. Arrigo, Eileen E. Hofmann, Gert L. Van Dijken

CCPO Publications

Previous studies showed that satellite‐derived estimates of chlorophyll a in coastal polynyas over the Antarctic continental shelf are correlated with the basal melt rate of adjacent ice shelves. A 5‐km resolution ocean/sea ice/ice shelf model of the Southern Ocean is used to examine mechanisms that supply the limiting micronutrient iron to Antarctic continental shelf surface waters. Four sources of dissolved iron are simulated with independent tracers, assumptions about the source iron concentration for each tracer, and an idealized summer biological uptake. Iron from ice shelf melt provides about 6% of the total dissolved iron in surface waters. The contribution from …

Modeling The Seasonal Cycle Of Iron And Carbon Fluxes In The Amundsen Sea Polynya, Antarctica, P. St-Laurent, P. L. Yager, R. M. Sherrell, H. Oliver, M. S. Dinniman, S. E. Stammerjohn

CCPO Publications

The Amundsen Sea Polynya (ASP) is distinguished by having the highest net primary production per unit area in the coastal Antarctic. Recent studies have related this high productivity to the presence of fast-melting ice shelves, but the mechanisms involved are not well understood. In this study we describe the first numerical model of the ASP to represent explicitly the ocean-ice interactions, nitrogen and iron cycles, and the coastal circulation at high resolution. The study focuses on the seasonal cycle of iron and carbon, and the results are broadly consistent with field observations collected during the summer of 2010–2011. The simulated …

A Comparison Of Global Estimates Of Marine Primary Production From Ocean Color, Mary-Elena Carr, Marjorie A. M. Friedrichs, Marjorie Schmeltz, Maki Noguchi Aita, David Antoine, Kevin R. Arrigo, Ichio Asanuma, Oliver Aumont, Richard Barber, Michael Behrenfeld

CCPO Publications

The third primary production algorithm round robin (PPARR3) compares output from 24 models that estimate depth-integrated primary production from satellite measurements of ocean color, as well as seven general circulation models (GCMs) coupled with ecosystem or biogeochemical models. Here we compare the global primary production fields corresponding to eight months of 1998 and 1999 as estimated from common input fields of photosynthetically-available radiation (PAR), sea-surface temperature (SST), mixed-layer depth, and chlorophyll concentration. We also quantify the sensitivity of the ocean-color-based models to perturbations in their input variables. The pair-wise correlation between ocean-color models was used to cluster them into groups …

Absorption And Backscattering In The Beaufort And Chukchi Seas, Jian Wang, Glenn F. Cota, David A. Ruble

CCPO Publications

Bio-optical observations were made during August 2000 in the Beaufort and Chukchi Seas. Chlorophyll a concentration (Chl) ranged from 0.068 to 18.5 mg chl m^-3. Both total particulate and phytoplankton absorption at 443 nm were closely correlated with chlorophyll concentration. Linear spectral relationships were observed for phytoplankton absorption. The chlorophyll-specific absorption of phytoplankton at 443 nm was nearly constant at 0.013 m² (mg chl)^-1, but particulate absorption due to nonpigmented particulates at 443 nm was highly variable. There was no strong correlation between chlorophyll concentration and absorption by soluble materials or nonpigmented particulates. Absorption, scattering, …

The Role Of Feeding Behavior In Sustaining Copepod Populations In The Tropical Ocean, J. D. Wiggert, A. G. E. Haskell, G.-A. Paffenhofer, E. E. Hofmann, J. M. Klinck

CCPO Publications

A fundamental question regarding marine copepods is how the many species coexist and persist in the oligotrophic environment (i.e. Hutchinson’s paradox). This question is addressed with a stochastic, object-oriented Lagrangian model that explicitly simulates the distinct foraging behaviors of three prominent tropical species: Clausocalanus furcatus, Paracalanus aculeatus and Oithona plumifera. The model also individually tracks all prey cells. Each particle’s motion combines sinking, turbulent diffusion and active swimming when applicable. The model successfully simulates observed size partitioned carbon uptake rates. Based on the model results, the wide-ranging translational ambit employed by C. furcatus is best suited for the acquisition …

Satellite Evidence Of Hurricane-Induced Phytoplankton Blooms In An Oceanic Desert, S. M. Babin, J. A. Carton, T. D. Dickey, J. D. Wiggert

CCPO Publications

The physical effects of hurricanes include deepening of the mixed layer and decreasing of the sea surface temperature in response to entrainment, curl-induced upwelling, and increased upper ocean cooling. However, the biological effects of hurricanes remain relatively unexplored. In this paper, we examine the passages of 13 hurricanes through the Sargasso Sea region of the North Atlantic during the years 1998 through 2001. Remotely sensed ocean color shows increased concentrations of surface chlorophyll within the cool wakes of the hurricanes, apparently in response to the injection of nutrients and/or biogenic pigments into the oligotrophic surface waters. This increase in post-storm …

Bio-Optical Properties Of The Labrador Sea, Glenn F. Cota, W. Glen Harrison, Trevor Platt, Shubha Sathyendranath, Venetia Stuart

CCPO Publications

Three cruises were conducted during fall and spring in the Labrador Sea to investigate the effects of bio-optical properties on satellite retrievals of phytoplankton chlorophyll in this important high-latitude ecosystem. Taxon-specific and regional differences were found. Diatoms had similar to 1.5 lower chlorophyll-specific absorption but significantly higher reflectance ratios than prymnesiophytes. Particulate absorption at 443 nm for total, phytoplankton, and "detrital'' fractions was related to chlorophyll, but values were lower than reported for lower latitudes. Decreased particulate absorption is attributed primarily to pigment packaging, while low backscattering to scattering ratios result from a lower relative abundance of bacteria and picophytoplankton …

Modeling The Effects Of Doliolids On The Plankton Community Structure Of The Southeastern Us Continental Shelf, A. G. Edward Haskell, Eileen E. Hofmann, Gustav-Adolf Paffenhofer, Peter G. Verity

CCPO Publications

A model of the lower trophic levels that consists of a system of coupled ordinary differential equations was developed to investigate the time-dependent behavior of doliolid populations associated with upwelling features on the outer southeastern US continental shelf. Model equations describe the interactions of doliolids with two phytoplankton size fractions, five copepod developmental stages and a detrital pool. Additional equations describe nitrate and ammonia. Model dynamics are based primarily upon data obtained from field and laboratory experiments for southeastern US continental shelf plankton populations. Variations on a reference simulation, which represents average upwelling conditions without doliolids, were carried out to …

Modeling Nutrient And Plankton Processes In The California Coastal Transition Zone: 3. Lagrangian Drifters, J. R. Moisan, Eileen E. Hofmann

CCPO Publications

Two types of numerical Lagrangian drifter experiments were conducted, using a set of increasingly complex and sophisticated models, to investigate the processes associated with the plankton distributions in the California coastal transition zone (CTZ). The first experiment used a one-dimensional (1-D; vertical) time-dependent physical-bio-optical model, which contained a nine-component food web. Vertical velocities, along the track of simulated Lagrangian drifters, derived from a three-dimensional (3-D), primitive equation circulation model developed to simulate the flow observed within the CTZ; were used to parameterize the upwelling and downwelling processes. The second experiment used 880 simulated Lagrangian drifters from a 3-D primitive equation …

Continental Shelf Processes Affecting The Oceanography Of The South Atlantic Bight. Progress Report, 1 June 1980-1 June 1981, Larry P. Atkinson

CCPO Publications

(Introduction) In the past year we executed our largest field effort to date, GABEX-1. The vast amount of data gathered has now been reduced to workable form and we report on some of the first results in this report. The GABEX-1 measurements combined with other observations in the last year have greatly increased our understanding of the South Atlantic Bight during the spring transition period when the shelf goes from horizontal to vertical stratification.

This progress report contains selected reprints, drafts, and parts of technical reports that represent our work over the past three years.

The Chemical And Biological Effect Of A Gulf Stream Intrusion Off St. Augustine, Florida, Larry P. Atkinson, Gustav-Adolf Paffenhöfer, William M. Dunstan

CCPO Publications

During a 3-day anchor station in shelf waters off St. Augustine, Florida we observed the effect of an intruding mass of deeper Gulf Stream water. The shelf waters were relatively low in nutrients and salinity while the Gulf Stream waters were high in salinity and nutrients. Onshore currents correlated with increases in nitrate and chlorophyll concentrations.

The advection of higher nutrient Gulf Stream water coincided with high chlorophyll (∼ mg chl a m⁻³) concentrations and dense populations of Phaeocystis pouchetii (up to 3.12 × 10°1⁻¹). Zooplankton sampling was impossible in the bottom layer because of the …