Estimating iron and aluminum removal rates in the eastern equatorial Pacific Ocean using a box model approach.

a b s t r a c t Iron limitation plays an important role in maintaining the high-nitrate low-chlorophyll (HNLC) condition in the equatorial upwelling zone. The rate and depth of upwelling control Fe supply to the euphotic zone. This study constrains the transport fluxes and budget of two trace metals, Fe and Al, in the upper ocean. They are co-delivered to the eastern equatorial Pacific surface waters via the Equatorial Undercurrent and upwelling but show distinct biogeochemical cycling processes. We combine the results of the in situ measurements of dissolved Fe and Al (dFe and dAl) with the modeled velocity fields to calculate the physical fluxes. The model calculations are evaluated with the conservation of heat, volume transport, NO 3 and Si(OH) 4 budgets for the equatorial Pacific. The vertical flux due to upwelling provides averaged dFe and dAl supply rates of 1.45 mmol m , respectively. These estimates are equal to the net biological and chemical removal rates of dFe and dAl. The calculated dFe:C net removal ratio is in the range of 3-9 mmol:mol, which agrees with most other estimates. This suggests that the majority of net dFe removal is due to biological uptake in the upper water column. The results of this box model approach illustrate the usefulness of combining the modeled outputs and in situ measurements, which provide additional constraints on Fe transport and cycling in the equatorial Pacific and possibly other HNLC regions

Optimising the reproducibility of measurements of the post-IR IRSL signal from single-grains of K-feldspar for dating.

Achieving good environmental status in the Baltic Sea region requires decision support tools which are based on scientific knowledge across multiple disciplines. Such tools should integrate the complexity of the ecosystem and enable exploration of different natural and anthropogenic pressures such as climate change, eutrophication and fishing pressures in order to compare alternative management strategies. We present a new framework, with a Baltic implementation of the spatially-explicit end-to-end Atlantis ecosystem model linked to two external models, to explore the different pressures on the marine ecosystem. The HBM-ERGOM initializes the Atlantis model with high-resolution physical-chemical-biological and hydrodynamic information while the FISHRENT model analyses the fisheries economics of the output of commercial fish biomass for the Atlantis terminal projection year. The Baltic Atlantis model composes 29 sub-areas, 9 vertical layers and 30 biological functional groups. The balanced calibration provides realistic levels of biomass for, among others, known stock sizes of top predators and of key fish species. Furthermore, it gives realistic levels of phytoplankton biomass and shows reasonable diet compositions and geographical distribution patterns for the functional groups. By simulating several scenarios of nutrient load reductions on the ecosystem and testing sensitivity to different fishing pressures, we show that the model is sensitive to those changes and capable of evaluating the impacts on different trophic levels, fish stocks, and fisheries associated with changed benthic oxygen conditions. We conclude that the Baltic Atlantis forms an initial basis for strategic management evaluation suited for conducting medium to long term ecosystem assessments which are of importance for a number of pan-Baltic stakeholders in relation to anthropogenic pressures such as eutrophication, climate change and fishing pressure, as well as changed biological interactions between functional groups

Seasonal and inter-annual changes in the surface chlorophyll of the South China Sea

NASA; NSF; NSFC [90711006, 2011CB403500]The Hilbert-Huang Transform was applied to the satellite-derived monthly surface chlorophyll-a data and monthly blended satellite wind products from September 1997 to April 2010 to examine temporal trends in these time series. Using this new approach, we found an overall increasing trend in both the surface chlorophyll-a concentration and surface wind speed averaged over the entire South China Sea. Chlorophyll-a concentration increased by 12% between September 1997 and September 2003, and then decreased by 3% by April 2010. Wind speed increased by 21% between September 1997 and December 2005, but then decreased by 11%. The increasing trends followed by a period of decrease in both chlorophyll-a and wind speed time series are likely driven by the El Nino Southern Oscillation signal. The biggest change occurred in the deep basin region where the area averaged chlorophyll-a concentration increased by 20% between 1997 and 2010. This trend was primarily attributed to a 19% increase of the surface area of waters with monthly averaged chlorophyll-a concentration greater than 0.2 mg m(-3), called the high chlorophyll waters. The most pronounced change occurred in winter with the high chlorophyll surface area expanding from 56 to 64% of the South China Sea. Strong correlation between chlorophyll-a and wind speed in this region suggested that it is the enhanced wind-induced mixing in the winter that stimulates phytoplankton growth via increased vertical supply of nutrients. The obtained 13-year trends indicate that the physical-biological interactions also take place on inter-annual time scales in the South China Sea

Spatial distribution of Baltic sprat biomass for the 60 year simulation period.

<p>Spatial distribution of Baltic sprat biomass for the 60 year simulation period.</p

Relative (%) reduction of total nitrogen river load applied to certain Baltic Atlantis polygon according to the four nutrient load scenarios (#2–#5) and the changes in fishing mortality for the five fishing mortality scenarios (#6–#10).

<p>Scenario 1 is the baseline to compare the results against.</p

Time series evolution of Baltic Atlantis functional groups.

<p>Total biomass in metric tons of biological functional groups and total DIN (dissolved inorganic nitrogen) obtained from a 60-year reference run initialized with 2005 data.</p

Spatial distribution of bottom oxygen concentration for the Baltic Sea for the 60 year simulation period.

<p>Spatial distribution of bottom oxygen concentration for the Baltic Sea for the 60 year simulation period.</p

Relative changes (%) of equilibrium fish and Nephrops total stock biomasses (TSB), averaged over the final simulation year, given the three nutrient load reduction scenarios (#2–#4) evaluated economically relative to the status-quo scenario (#1), of the species groups included in the Baltic Atlantis model.

<p>Relative changes (%) of equilibrium fish and Nephrops total stock biomasses (TSB), averaged over the final simulation year, given the three nutrient load reduction scenarios (#2–#4) evaluated economically relative to the status-quo scenario (#1), of the species groups included in the Baltic Atlantis model.</p

Results of the four river load scenarios.

<p>Percentage of change of the biomass for the different biological functional groups compared to the status-quo scenario #1.</p