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Archive for New OCB Research – Page 20

Rapid warming and salinity changes mask acidification in Gulf of Maine waters

Posted by mmaheigan 
· Wednesday, February 20th, 2019 

Why don’t we see ocean acidification in over a decade of high-frequency observations in the Gulf of Maine? The answer lies in a recent decade of changes that raised sea surface temperature and salinity, and in turn dampened the expected acidification signal and caused the saturation states of calcite minerals to increase. From 2004 to 2014, sea surface temperatures in the Gulf of Maine were higher than any observations recorded in the region over the past 150 years. This greatly impacted both CO2 solubility and the sea surface carbonate system, as detailed in a recent paper in Biogeochemistry.

Over the 34 years of the time-series, the recent event is extreme, but interannual and decadal salinity and temperature variability also influenced carbonate system parameters, which makes it difficult to isolate and quantify an anthropogenic ocean acidification signal, especially if relying on shorter-term observations (Figure 1).

Figure 1: Modeled ΩAragonite (top panel) and pH (bottom panel) anomalies relative to monthly 2004 data. The red lines show trends prior to and after 2004, after which warming accelerated.

For those with a stake in profiting from or managing extractive resources that are susceptible to ocean acidification such as commercially important lobster and bivalves, understanding how ecosystems will be affected is critical. These analyses clearly demonstrate how physical processes can either accelerate or mitigate ocean carbonate system changes, thus confounding the detection of ocean acidification that is expected from increasing atmospheric carbon dioxide. To assess whether an ecosystem or species is at risk or aided by such processes, it is important to observe, understand, and be able to model all sources of carbonate system variability.

Authors:
Joe Salisbury and Bror Jönsson (Both at Ocean Processes Analysis Laboratory, University of New Hampshire)

Biological and physical controls on estuarine nitrous oxide emissions

Posted by mmaheigan 
· Tuesday, February 5th, 2019 

Nitrous oxide (N2O) is a potent greenhouse gas with rising atmospheric concentrations. Atmospheric emissions of N2O are predicted to increase with continued anthropogenic perturbation of the nitrogen cycle, yet the magnitude of these emissions is uncertain, particularly in coastal systems where N2O fluxes are poorly constrained. How do N2O emissions from a eutrophic estuary vary in space and time?

Figure 1: Depth profiles of nitrous oxide (N2O) (circles), salinity (dashed line), and dissolved oxygen (solid line) in the Chesapeake Bay at three stations. Solid circles indicate oversaturation of N2O with respect to equilibrium with the atmosphere, and open circles indicate undersaturation.

In a recent publication in Estuaries and Coasts, Laperriere et al. (2018) examined how physical and biological processes influence the distribution of N2O in Chesapeake Bay using dissolved gas measurements (N2O and N2/Ar) and stable isotope tracer incubations. During stratified summer conditions, the mesohaline region of the Chesapeake Bay was always a source of N2O to the atmosphere. The highest N2O concentrations occurred in the pycnocline at the interface between reducing bottom waters and oxygenated surface waters (Figure 1). Vertical mixing of surface waters across the pycnocline caused elevated rates of ammonia oxidation, a biological source of N2O, and resulted in the accumulation of nitrite (NO2–) below the pycnocline. During periods of weak mixing, ammonia oxidation rates and N2O concentrations were lower, and low dissolved oxygen concentrations below the pycnocline set the stage for N2O consumption via denitrification (Figure 1). The interplay between biological and physical processes controlling fluctuations in N2O concentration was examined using a mass balance approach. Mass balance estimates indicated that both biological processes and physical transport contribute to local changes in N2O concentration. The authors suggest that the fate of N2O during stratified summer conditions is governed by vertical mixing across the pycnocline, controlling whether N2O is released to the atmosphere or consumed at depth.

 

Authors:
Sarah M. Laperriere (University of California, Santa Barbara)
Nicholas J. Nidzieko (University of California, Santa Barbara)
Rebecca J. Fox (Washington College)
Alexander W. Fisher (University of California, Santa Barbara)
Alyson E. Santoro (University of California, Santa Barbara)

Evidence against an Arctic Ocean methane bomb

Posted by mmaheigan 
· Tuesday, February 5th, 2019 

Gas hydrates are an ice-like storehouse of the greenhouse gas methane found in continental margins of the world ocean. Warming waters can cause hydrates to decompose and release ancient methane to overlying sediment and waters. The continental shelves of the Arctic Ocean have been thought of as “ground zero” for the potential release of methane from hydrates, since the Arctic is warming rapidly and hydrates are found at relatively shallow water depths there. Another potential ancient methane input to Arctic shelf waters is the methane produced by microorganisms from the gradual thawing of permafrost carbon within seafloor sediment and/or transported to the shelf from terrestrial permafrost via rivers. But, can large stores of ancient-sourced methane reach surface waters and enter the atmosphere, contributing to greenhouse warming?

Figure caption: Map showing the fraction of methane in each surface water sample that was derived from ancient hydrate or permafrost, on a scale from 0 (modern, 0% ancient; indigo) to 1 (100% ancient; yellow). While some of the near-shore surface methane samples have a significant (~50%) ancient component, in waters deeper than 20 m, the surface water methane was mostly (90-95%) derived from modern sources.

To answer this question and understand the role of these ancient sources of methane (hydrates and permafrost), the authors of a 2018 study in Science Advances measured the natural abundance of radiocarbon (14C) in dissolved methane in the shallow shelf waters of the Alaskan Arctic Ocean (U.S. Beaufort Sea); methane derived from ancient sources has little to no measurable 14C because of radioactive decay over time. The 14C-methane results show that ancient sources are contributing methane to the study area’s waters, as the authors predicted. However, ancient methane emitted to seawater can be consumed by microorganisms or transported away by currents before reaching the atmosphere, though these mechanisms have not been known to be effective at removing methane in waters <100 m. This study revealed that these removal processes are surprisingly efficient in shallow shelf waters, especially at the study area’s deepest stations of 30 and 40 m depth, where only ~10% of the methane in surface waters was derived from ancient sources. These results add to a growing body of evidence against the likelihood of a large methane emission to the atmosphere occurring from ancient sources like hydrates, since the authors expect that methane removal processes in the water column are much more efficient in waters 100s of meters deep, where the bulk of the hydrate reservoir resides.

 

Authors:
K.J. Sparrow (University of Rochester; current address: Florida State University)
J.D. Kessler (University of Rochester)
J.R. Southon (University of California Irvine)
Garcia-Tigreros (University of Rochester)
K.M. Schreiner (University of Minnesota Duluth)
C.D. Ruppel (USGS)
J.B. Miller (University of Colorado Boulder; NOAA)
S.J. Lehman (University of Colorado Boulder)
Xu (University of California Irvine)

Dust-borne iron in the Southern Ocean was more bioavailable during glacial periods

Posted by mmaheigan 
· Wednesday, January 23rd, 2019 

The Southern Ocean is iron (Fe)-limited, and increased fluxes of dust-borne Fe to the Southern Ocean during the Last Glacial Maximum (LGM) have been associated with phytoplankton growth and CO2 drawdown. Dust contains different mixes of Fe-bearing minerals, depending on the source region. Fe(II) silicate minerals from physical weathering are more bioavailable than Fe(III) oxyhydroxide minerals from chemical weathering. The Fe(II) silicates are dominant in dust sources that have been weathered from bedrock by glaciers in Patagonia, but the impact of glacial activity on dust-borne Fe speciation (Fe oxidation state and mineral composition) and bioavailability over the last glacial cycle has not previously been quantified.

Figure 1. The fraction of Fe(II) in dust (Fe(II)/Fetotal, dominated by Fe(II) silicates, shown as blue dots connected with dotted lines on blue axes) in marine sediment cores from (A) the South Atlantic and (B) the South Pacific plotted with the total dust flux (grey lines on grey axes).

A recent study in PNAS reconstructs the speciation of dust-borne Fe over the last glacial cycle in South Atlantic and South Pacific marine sediment cores using Fe K-edge X-ray absorption spectroscopy. The authors observed that the highly bioavailable Fe(II) silicate content of dust-borne Fe is higher in both regions during cold glacial periods, suggesting that a given flux of Fe is more bioavailable in glacial versus interglacial periods (Figure 1). Therefore, all Fe cannot be considered equal in biogeochemical models working on glacial-interglacial timescales. The bioavailability of a given flux of Fe at the LGM was likely a dominant driver of phytoplankton growth, with more bioavailable Fe driving increased phytoplankton activity and associated atmospheric CO2 drawdown and subsequent cooling. The observed association between glacial periods and increased Fe bioavailability in the Southern Ocean may indicate an important positive feedback mechanism between glacial activity and cold glacial temperatures through Fe speciation and the efficiency of the biological pump.

Paper link: https://doi.org/10.1073/pnas.1809755115

Authors:
Elizabeth M. Shoenfelt (Lamont-Doherty Earth Observatory, Columbia University)
Gisela Winckler (Lamont-Doherty Earth Observatory, Columbia University)
Frank Lamy (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)
Robert F. Anderson (Lamont-Doherty Earth Observatory, Columbia University)
Benjamin C. Bostick (Lamont-Doherty Earth Observatory, Columbia University)

 

The past, present, and future of artificial ocean iron fertilization experiments

Posted by mmaheigan 
· Wednesday, January 23rd, 2019 

Since the beginning of the industrial revolution, human activities have greatly increased atmospheric CO2 concentrations, leading to global warming and indicating an urgent need to reduce global greenhouse gas emissions. The Martin (or iron) hypothesis suggests that ocean iron fertilization (OIF) could be a low-cost effective method for reducing atmospheric CO2 levels by stimulating carbon sequestration via the biological pump in iron-limited, high-nutrient, low-chlorophyll (HNLC) ocean regions. Given increasing global political, social, and economic concerns associated with climate change, it is necessary to examine the validity and usefulness of artificial OIF (aOIF) experimentation as a geoengineering solution.

Figure 1. (a) Global annual distribution of surface chlorophyll concentrations (mg m-3) with locations of 13 aOIF experiments. Maximum and initial values in (b) maximum quantum yield of photosynthesis (Fv/Fm ratios) and (c) chlorophyll-a concentrations (mg m-3) during aOIF experiments. (d) Changes in primary productivity (ΔPP = [PP]post-fertilization (postf) ‒ [PP]pre-fertilization (pref); mg C m-2 d-1). (e) Distributions of chlorophyll-a concentrations (mg m-3) on day 24 after iron addition in the Southern Ocean iron experiment-north (SOFeX-N) from MODIS Terra Level-2 daily image and on day 20 in the SOFeX-south (SOFeX-S) from SeaWiFS Level-2 daily image (white dotted box indicates phytoplankton bloom during aOIF experiments). (f) Changes in nitrate concentrations (ΔNO3– = [NO3–]postf ‒ [NO3–]pref; μM). (g) Changes in partial pressure of CO2 (ΔpCO2 = [pCO2]postf ‒ [pCO2]pref; μatm). The color bar indicates changes in dissolved inorganic carbon (ΔDIC = [DIC]postf ‒ [DIC]pref; μM). The numbers on the X axis indicate the order of aOIF experiments as given in Figure 1a and are grouped according to ocean basins; Equatorial Pacific (EP) (yellow bar), Southern Ocean (SO) (blue bar), subarctic North Pacific (NP) (red bar), and subtropical North Atlantic (NA) (green bar).

A review paper published in Biogeosciences on aOIF experiments provides a thorough overview of 13 scientific artificial OIF experiments conducted in HNLC regions over the last 25 years. These aOIF experiments have demonstrated that iron addition stimulates substantial increases in phytoplankton biomass and primary production, resulting in drawdown of macro-nutrients and dissolved inorganic carbon (Figure 1). Many of the aOIF experiments have also precipitated community shifts from smaller (pico- and nano-) to larger (micro) phytoplankton. However, the impact on the net transfer of CO2 from the atmosphere to below the winter mixed layer via the biological pump is not yet fully understood or quantified and appears to vary with environmental conditions, export flux measurement techniques, and other unknown factors. These results, including possible side effects, have been debated among those who support and oppose aOIF experimentation, and many questions remain about the effectiveness of scientific aOIF, possible side effects, and international aOIF law frameworks. Therefore, it is important to continue undertaking small-scale, scientifically controlled studies to better understand natural processes in the HNLC regions, assess the associated risks, and lay the groundwork for evaluating the potential effectiveness and impacts of large-scale aOIF as a geoengineering solution to anthropogenic climate change. Additionally, this paper suggests considerations for the design of future aOIF experiments to maximize the effectiveness of the technique and begin to answer open questions under international aOIF regulations.

 

Authors:
Joo-Eun Yoon (Incheon National University)
Il-Nam Kim (Incheon National University)
Alison M. Macdonald (Woods Hole Oceanographic Institution)

Constraints on glacial overturning circulation and export production lead to answers about the carbon cycle

Posted by mmaheigan 
· Friday, January 4th, 2019 

One of the biggest unsolved mysteries in climate science concerns the dynamics and feedbacks of the ice age carbon dioxide (CO2) cycle.

At the height of the Pleistocene ice ages, the atmospheric CO2 concentration was about 1/3 lower than during the warm interglacial periods. Most scientists think that the CO2 that was missing from the atmosphere was in the deep ocean, but how and why remains unclear. In a study published in Earth and Planetary Science Letters, we compared different computer simulations of the ice age ocean with δ13C, radiocarbon (14C), and δ15N data from sea floor sediments.

We find that a weak and shallow Atlantic Meridional Overturning Circulation (6-9 Sv, or approximately half of today’s overturning rate) best reproduces the glacial sediment isotope data. Increasing the atmospheric soluble iron flux in the model’s Southern Ocean intensifies export production, carbon storage, and further improves agreement with glacial δ13C and δ15N reconstructions.

Figure Caption: Depth profiles of global mean δ13C, calculated using only grid boxes for which there exists Last Glacial Maximum data. Blue: Weak Atlantic circulation; Red: Strong Atlantic circulation; Green: Collapsed Atlantic circulation; Dashed: Extra iron in the Southern Ocean; Orange: Last Glacial Maximum Data.

Our best-fitting simulation (blue, dashed line in the figure) is a significant improvement over previous studies and suggests that both circulation and export production changes were necessary to maximize carbon storage in the glacial ocean. These findings provide an equilibrium glacial state, consistent with a combination of proxies, that can be used as a basis for simulations covering the last deglaciation time period. Understanding the different states that the global climate system can transit, and the characteristics of the transitions, is crucial to project possible outcomes of current climate change processes.

 

Authors:
Juan Muglia (Oregon State University)
Luke C. Skinner (Godwin Laboratory for Palaeoclimate Research, University of Cambridge)
Andreas Schmittner (Oregon State University)

234Th-based estimates show contrasting patterns of carbon attenuation through oxygen minimum and deficient zones

Posted by mmaheigan 
· Thursday, December 20th, 2018 

Oxygen minimum zones (OMZs) are thought to be regions of the global ocean where a greater percentage of the organic carbon associated with particles makes it to depth. Currently covering 8% of the world’s ocean area, these low oxygen regions are expected to expand as a result climate change. It is therefore vital to understand if and how OMZs could sequester more carbon via decreased attenuation in the water column. During the U.S. GEOTRACES Southeastern Tropical Pacific campaign along the 12°S line, a study published in Marine Chemistry examined the transport of particulate organic carbon (POC) within the Peruvian OMZ using the well-established 238U-234Th method. This included studying the functionally anoxic core of the OMZ, here referred to as the Peruvian Shelf oxygen deficient zone (ODZ, coast to 80°W) and the Offshore ODZ (80°W to 105°W).

Figure 1: The relationship between particulate organic carbon (POC) exported at 100 m below the base of the euphotic zone (sunlight upper ocean) and surface net primary production (NPP) in the Southeastern Tropical Pacific (colors, this study) and prior study locations including NAtl (NABE, North Atlantic Bloom Experiment), NWPac (K2, Northwest Pacific), CPac (ALOHA, Central North Pacific), EqPac (Equatorial Pacific), SO (KIWI, Southern Ocean), and NEPac (Station Papa, Northeast Pacific).

As predicted, the South Pacific OMZ (105°W to 155°W) exported a larger fraction of POC below the productive sunlit upper ocean than what has been observed in non-OMZ waters globally (right side, Figure 1). The ODZ waters, on the other hand, showed a greater attenuation of POC (left side, Figure 1) in this same region of the water column (left side, Figure 1). With decreased POC attenuation observed in the OMZ and increased attenuation in the ODZ, these results suggest that global expansion of low-oxygen waters may have a more complex effect on regional carbon sequestration than predicted. Simultaneous observations of low light transmission, nitrate minima, nitrite maxima, and deep secondary chlorophyll maxima in these ODZ regions suggest that complex bacterial community dynamics play a role in increased attenuation through these zones. With ODZs and OMZs predicted to grow worldwide with climate change, these areas require further large-scale and seasonal studies to assess the permanency of these attenuation features and the impact of high Gyre and lower ODZ transfer of POC on the overall efficiency of carbon export in the Pacific.

 

Authors:
Erin Black (Dalhousie University)
Ken Buesseler (Woods Hole Oceanographic Institution)
Steven Pike (Woods Hole Oceanographic Institution)
Phoebe Lam (University of California Santa Cruz)

New BioGEOTRACES data sets: Connecting pieces of the microbial biogeochemical puzzle

Posted by mmaheigan 
· Wednesday, December 19th, 2018 

Microorganisms play a central role in the transfer of matter and energy in the marine food web. Microbes depend on micronutrients (e.g. iron, cobalt, zinc, and a host of other trace metals) to catalyze key biogeochemical reactions, and their metabolisms, in turn, directly affect the cycling, speciation, and bioavailability of these compounds. One might therefore expect that marine microbial community structure and the functions encoded within their genomes might be related to trace metal availability in the ocean. The overall productivity of marine ecosystems—i.e. the amount of carbon fixed through photosynthesis—could in turn be influenced by trace metal concentrations.

For over a decade, the international GEOTRACES program has been mapping the distribution and speciation of trace metals across vast ocean regions. Given the important relationship between trace metals and the function of marine ecosystems, biological oceanographers collaborate with GEOTRACES scientists to simultaneously probe the biotic communities at some sampling sites, allowing these biological data to be interpreted in the context of detailed chemical and physical measurements.

Figure 1. Locations and depths of samples. (a) Global map of sample locations. Single cell genomes are represented by miniaturized stacked dot-plots (each dot represents one single cell genome), with organism group indicated by color, and cells categorized as “undetermined” if robust placement within known phylogenetic groups failed due to low assembly completeness/quality or missing close references. Larger points correspond to stations on associated GEOTRACES sections where metagenomes were also collected. (b) Depth distribution of metagenome samples along each of the four GEOTRACES sections. Transect distances are calculated relative to the first station sampled in the indicated orientation. For clarity, the depth distribution of samples collected below 250 m are not shown to scale (ranging from 281–5601 m). Adapted from Berube et al. (2018) Sci. Data 5:180154 and Biller et al. (2018) Sci. Data 5:180176.

Two recent papers published in Scientific Data describes two new, large-scale biological data sets that will facilitate studies aimed at understanding how microbes and metals relate to one another. Collected on four different sets of GEOTRACES cruises (Figure 1), these papers report the public availability of hundreds of single cell genomes and microbial community metagenomes from the Pacific and Atlantic Oceans. The single cell genomes focus on the marine photosynthetic bacteria Prochlorococcus and Synechococcus and how they and other community members vary in different regions of the ocean. The metagenomic sequences provide snapshots of the entire microbial community found in each of these samples, yielding a broad overview of which microbes—and which genes, including those important for understanding nutrient cycling—are found in each sample. These two datasets are complementary and further enhanced by the wealth of chemical and physical data collected by GEOTRACES scientists on the same water samples. In particular, iron is of key interest, since it often limits primary productivity. These data sets can directly link iron availability with microbial community structure and gene content across ocean basins.

With these data, researchers can now ask questions such as how microbes have evolved in response to the availability or limitation of key nutrients and explore which organisms may be contributing to biogeochemical cycles in different parts of the global ocean. The extensive suite of chemical and physical measurements associated with these sequence data underscore their potential to reveal important relationships between trace metals and the microbial communities that drive biogeochemical cycles. These data sets also encourage cross-disciplinary collaborations and provide baseline information as society faces the challenges and uncertainties of a changing climate.

Authors:
Paul M. Berube (Massachusetts Institute of Technology)
Steven J. Biller (Massachusetts Institute of Technology; current affiliation: Wellesley College)
Sallie W. Chisholm (Massachusetts Institute of Technology)

Alternative particle formation pathways identified in the Equatorial Pacific’s biological pump

Posted by mmaheigan 
· Tuesday, November 27th, 2018 

The ocean is one of the largest sinks of atmospheric carbon dioxide (CO2) on our planet, driven in part by CO2 uptake by phytoplankton in the upper ocean during photosynthesis. Eventually, a portion of the resulting organic carbon is transported to depth, where it is sequestered from the atmosphere for centuries or even millennia. Our current understanding of the biological pump is based on the export of organic material in the form of large, fast-sinking (hundreds of meters per day) particles. However, using lipids as biomarkers, a recent study from the Equatorial Pacific Ocean published in JGR Biogeosciences showed that fast-sinking particles are refractory and distinctly different from plankton in the mixed layer, whereas slow-sinking particles were more labile and had a more similar composition to mixed layer particles (Fig. 1).

Figure 1. Particle lipid compositions for different particle fractions: ML = homogenous mixed layer particles, SU = suspended, SS = slow-sinking, and FS = fast-sinking of a) labile compounds known as unsaturated fatty acids synthesized by phytoplankton that provide a lot of energy for heterotrophs and b) sterols, including cholesterol (dark blue), which can be a biomarker for heterotrophy. Mixed layer particles are the most labile, showing the least degree of heterotrophic reworking, as expected. However, fast-sinking particles are most dissimilar from those in the mixed layer, with only a small proportion of labile compounds and a high degree of heterotrophic reworking.

The authors proposed a slower, less efficient export pathway, by which phytoplankton initially aggregate to smaller, slower-sinking detrital particles and then gradually form highly degraded, larger particles that sink to depth. Since smaller particles are respired more rapidly than larger particles, the proportion of phytoplankton-captured atmospheric CO2 being stored in the deep ocean is likely reduced, particularly in regions dominated by smaller phytoplankton such as the Equatorial Pacific. This study clearly demonstrates the need for improved representation of a wider range of particle dynamics in models of the ocean’s biological pump.

 

Authors:
E. L. Cavan (University of Tasmania, previously University of Southampton)
S. Giering (National Oceanography Centre)
G. Wolff (University of Liverpool)
M. Trimmer (Queen Mary University London)
R. Sanders (National Oceanography Centre)

Artificial light from sampling platforms changes zooplankton behavior

Posted by mmaheigan 
· Monday, November 26th, 2018 

When designing sampling we make generally accepted assumptions that what we collect is representative of what is “normal” or naturally occurring at the place, time, and depth of collection. However, a recent study in Science Advances revealed that this might not be true. During round-the-clock shipboard sampling, lights used at night can actually be a form of pollution that disrupts the diel cycle of zooplankton vertical migration.

Effect of light pollution on krill from a ship (left), diel vertical migration in natural dark conditions (middle) and effect of moonlight (right). Figure by Malin Daase (UiT).

Using a Autonomous Surface Vehicle the authors documented zooplankton behavioral patterns of light avoidance never previously seen. The study compared results from high Arctic polar night (unpolluted light environment for an extended time), to near ship samples. During months of near constant darkness in the Arctic, there was still a diel vertical migration of zooplankton limited to the upper 30 m of the water column and centered around the local sun noon. Contrasting the results from light-polluted and unpolluted areas, the authors observed that the vast majority of the pelagic community exhibit a strong light-escape response in the presence of artificial light (both ship light and even headlamps from researchers in open boats). This effect was observed down to 100 m depth and 190 m from the ship. These results suggest that artificial light from traditional sampling platforms may bias studies of zooplankton abundance and diel migration within the upper 100 m. These findings underscore the need for alternative sampling methods such as autonomous platforms, particularly in dim-light conditions, to collect more accurate and representative physical and biological data for ecological studies. In addition to research cruises and sampling, anthropogenic light pollution from predicted increases in shipping, oil and gas exploration, and light-fishing are anticipated to impact the diel rhythms of zooplankton behavior all around the globe.

Authors:
Jørgen Berge (Norwegian University of Technology and Science; UiT The Arctic University of Norway)
Martin Ludvigsen (Norwegian University of Technology and Science; University Centre in Svalbard)
Maxime Geoffroy (UiT The Arctic University of Norway, Memorial University of Newfoundland)
Jonathan H. Cohen (University of Delaware)
Pedro R. De La Torre (Norwegian University of Technology and Science)
Stein M. Nornes (Norwegian University of Technology and Science)
Hanumant Singh (Northeastern University)
Asgeir J. Sørensen (Norwegian University of Technology and Science)
Malin Daase (Norwegian University of Technology and Science)
Geir Johnsen (Norwegian University of Technology and Science; Norwegian University of Technology and Science)

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shells ship-based observations shorelines siderophore silica silicate silicon cycle sinking sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST state estimation stoichiometry subduction submesoscale subpolar subtropical sulfate surf surface surface ocean Synechococcus technology teleconnections temperate temperature temporal covariations thermocline thermodynamics thermohaline thorium tidal time-series time of emergence titration top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features trawling Tris trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport warming water clarity water mass water quality waves weathering western boundary currents wetlands winter mixing zooplankton

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