Global Dataset of Particle Flux Measurements

 

This dataset includes sinking particle flux measurements that I have collated from a suite of different oceanographic programs, some of which I have been involved in and many of which I have not.  A large portion of the data comes from the  California Current Ecosystem Long-Term Ecological Research (CCE LTER) program and is freely available from the CCE LTER DataZoo website.  Sinking particle flux measurements in this dataset are made by one of two different methodological approaches.  The first is drifting sediment traps.  These drifting sediment traps are essentially fancy buckets that the scientists deploy on a rope attached to a surface float.  They let the sediment traps drift for a period of days while collecting all particles that sink into the sediment traps.  They then measure the total mass and elemental composition of collected particles in order to estimate (among other things) the flux of carbon into the deep ocean.  The second method used to measure particle flux in this dataset is 238U-234Th disequilibrium (uranium-thorium disequilibrium).  This method is an indirect chemical proxy approach that takes advantage of the radioactivity and chemical characteristics of 238U and its daughter ion 234Th.  238U is radioactive but has a very long half life (4.5 billion years).  238U occurs naturally in the ocean at very low concentrations and is "conservative".  That means it behaves like a salt.  It does not stick to particles and organisms do not use it.  Basically, if we know the salinity of the water, we know how much 238U there will be.  238U decays into 234Th, which has a much shorter half life of only 24 days.  Because 234Th has a much shorter half life than its parent isotope, the two should reach "secular equilibrium".  That means that if you took some seawater, put it in a jar, and left it on your desk for a few months, the 238U and 234Th would reach an equilibrium such that 234Th was decaying away at exactly the rate it was being produced from the decay of 238U.  Another way to think of this, is that the two isotopes, in a closed system, would always wind up having the exact same ratio of their abundances and that ratio of their abundances would be set by the ratio of their half lives.  That is how it would work in a closed system.  However, the ocean is not a closed system and uranium and thorium have different chemical properties.  234Th sticks to particles.  When those particles sink from the surface ocean, they take 234Th with them.  Thus when we actually measure 234Th in the surface ocean, we find less thorium than we would expect based on the amount of 238U in the water.  The amount of "missing" 234Th is related to how many particles sank over a period of time set by the average lifetime of 234Th (approximately one month).  Thus by measured 234Th we can estimate how much carbon has been exported out of the surface ocean on sinking particles during a roughly one month period of time before we sampled.

 

While the scientists were making these measurements, they also measured many other physical, chemical, and biological properties that can be used to determine what processes drive variability in sinking particle flux.  However, since this dataset comes from many different projects, not all properties were measured in all projects.  Hence there is a lot of "missing" data that is represented as "NaN" to indicate that a measurement was not taken.  Since this data comes from many different scientists and many different projects, I have also included a column "Source" that shows manuscripts indicating the methods that the different scientists used and also explaining who should be credited with this data.  However, since you do not need to know that data in order to use this data set, that column is hidden by default.

 

Global Particle Flux Data.xlsx

 

Data Columns:

 Region = region of the ocean where the study took place

 Date Deployed = date that sediment trap was deployed (for sediment trap measurements only)

 Date Recovered = date that sediment trap was recovered (for sediment trap measurements only)

 Longitude = longitude at which the samples were collected (units = degrees west)

 Latitude = latitude at which the samples were collected (units = degrees west)

 Depth of the Euphotic Zone = the depth at which light decreases to a level that it no longer allows photosynthesis (unit = meters)

 Nitracline Depth = the depth at which nitrate concentrations increase substantially (unit = meters)

 Surface Nitrate = Nitrate concentration at the surface ocean above the sediment trap (unit = micromoles of nitrogen per liter seawater).  NItrate is the most abundant nitrogen-containing nutrient available to phytoplankton.

 Surface Silica =  Dissolved silicate (silicic acid) concentration at the surface ocean above the sediment trap (unit = micromoles of silicon per liter of seawater).  Silicic acid is the most abundant phosphorus-containing nutrient available to phytoplankton.

 Surface Phosphate =  Phosphate concentration at the surface ocean above the sediment trap (unit = micromoles of phosphate per liter of seawater).  Phosphate is the most abundant phosphorus-containing nutrient available to phytoplankton.

 Surface Ammonium = Ammonium concentration at the surface ocean above the sediment trap (unit = micromoles of nitrogen per liter of seawater).  Ammonium is the most easily-utilized nitrogen-containing nutrient available to phytoplankton and is rapidly recycled in the surface ocean.

 Surface Chlorophyll a = Chlorophyll a concentration at the surface ocean above the sediment trap (unit = micrograms of chlorophyll per liter of seawater). Chlorophyll a is the most important photosynthetic pigment found in nearly all plants and phytoplankton.

 Surface Phaeopigments = Phaeopigment concentration at the surface ocean above the sediment trap (unit = micrograms of chlorophyll per liter of seawater). Phaeopigments are a byproduct of chlorophyll a that is most frequently created when zooplankton consume phytoplankton and the chlorophyll gets acidified in their guts

 Vertically-integrated Chlorophyll a = The sum of all chlorophyll a in a vertical column above the sediment trap (unit = milligrams of chlorophyll per meter squared of seawater).

 Vertically-integrated Phaeopigments = The sum of all phaeopigments in a vertical column above the sediment trap (unit = milligrams of chlorophyll per meter squared of seawater).

 Surface Particulate Organic Carbon = total amount of organic carbon contained in particles at the surface above the sediment trap (unit = micromoles of carbon per liter).  It is equal to the sum of the organic carbon in phytoplankton + protistan zooplankton + heterotrophic bacteria + dead organic matter

 Surface Particulate Organic Nitrogen = total amount of nitrogen contained in particles at the surface above the sediment trap (unit = micromoles of nitrogen per liter).  It is equal to the sum of the nitrogen in phytoplankton + protistan zooplankton + heterotrophic bacteria + dead organic matter

 Vertically-integrated Particulate Organic Carbon = total amount of organic carbon contained in particles in a vertical column of water above the sediment trap (unit = milligrams of carbon per meter squared).  It is equal to the sum of the organic carbon in phytoplankton + protistan zooplankton + heterotrophic bacteria + dead organic matter

 Vertically-integrated Particulate Organic Nitrogen = total amount of nitrogen contained in particles in a vertical column of water above the sediment trap (unit = milligrams of nitrogen per meter squared).  It is equal to the sum of the organic nitrogen in phytoplankton + protistan zooplankton + heterotrophic bacteria + dead organic matter

 Primary production = vertically-integrated net bicarbonate uptake by phytoplankton at all depths in a vertical column of water above the sediment trap (units = milligrams of carbon per meter squared of seawater per day)

 Sinking Carbon Flux (Base of the Euphotic Zone) = organic carbon flux of sinking particles at a depth equal to the base of the euphotic zone (units = milligrams of organic carbon per meter squared per day).  Measuring carbon flux at this depth allows us to figure out how much carbon is actually leaving the sunlit surface ocean and entering the "Twilight Zone".  See column 'Depth of the Euphotic Zone' to find out what that depth actually is.

 Sinking Carbon Flux (100 m deeper than the base of the Euphotic Zone) = organic carbon flux of sinking particles at a depth equal to 100 m deeper than the base of the euphotic zone (units = milligrams of organic carbon per meter squared per day).  Comparison of carbon flux at this depth to carbon flux at the base of the euphotic zone allows us to estimate how efficiently organic carbon is transported through the "Twilight Zone" and into the deep sea.