Nitracline depth (1 µmol/L)
Nitracline depth: where nitrate reaches 1 umol/L, interpolated between the bracketing samples
mkey nitracline_depthP06 units ULAAseries nitracline_depth
one value per cast One value per cast. This measurement is worked out once for each cast rather than read at every depth, so it has no depth profile and no anomaly against a normal; its values are rows of sample_measurement, not of obs_env.
CalCOFI holds 4,060 values of it from 4,060 sampling events in one dataset, 2004–2026, one per cast.R Nitrate is used up in the sunlit surface layer; the nitracline is where it reappears, and a shallow nitracline means nutrients within reach of light and so of phytoplankton, which is why it tracks upwelling and El Niño off California.C
- 4,060
- values
- 0
- flagged
- 2004–2026
- years
- 1
- dataset
- 10 of 12
- months
Measured in
1 dataset
i
One row per series, one cell per year, darker with more values — the same strip the front
door draws per dataset and a species page draws per taxon. Each row is one dataset's own
measurement_type; the label is written once, in the title above.
i
One row per series, one cell per year, darker with more values — the same strip the front door draws per dataset and a species page draws per taxon. Each row is one dataset's own measurement_type; the label is written once, in the title above.
-
series
nitracline_depth· source columnest_nitrate_sta_corrone value per cast no flag at this grain no P01 concept
Explorerdb-queryThis page as JSON R · Python · Parquet
Every way in 6 ways · Parquet · R · Python · JSON
Read from measurements.json of release v2026.11.05, written at release by calcofi4db::build_measurements_catalog() beside taxa.json. The catalog's index is /measurements/; the JSON-LD on this page is a schema.org/DefinedTerm in the NERC P01 term set with a PropertyValue per series.
Explorerdb-querySELECT * FROM read_json('…/v2026.11.05/catalog.json')
-- objects[] WHERE table = 'sample_measurement'
-- then filter the rows:
-- measurement_type IN ('nitracline_depth')library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "sample_measurement") |> filter(measurement_type %in% c("nitracline_depth"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM sample_measurement WHERE measurement_type IN ('nitracline_depth')").df()How it is measured no method registered yet
No method row is registered for this measurement yet (metadata/measurement_method.csv).
Why it matters 4 ways to say it · EOV Nutrients
the GOOS specification sheet for this Essential Ocean Variable lists it
other ways to say why · 3
- The depth at which nitrate reaches 1 µmol/L, interpolated between the two samples that bracket it; the CTD version uses the bottle-fitted sensor estimate, the bottle version the bottle database itself (Rasmus Swalethorp, SIO, 2026-09-24). needs a citation before it can be the pick
- Wikipedia Nutricline source
- Wikipedia The deep chlorophyll maximum (DCM), also called the subsurface chlorophyll maximum, is the region below the surface of water with the maximum concentration of chlorophyll. The DCM generally exists at the same depth as the nutricline, the region of the ocean where the greatest change in the nutrient concentration occurs with depth. Deep chlorophyll maximum · CC BY-SA 4.0 · rev. 1380658017
Units and range m · 0 … 6500 declared · 0 flagged
m · P06 units ULAA
details
- bounds
- The registry declares
0 … 6500 mfornitracline_depth; a value outside it is dropped at the ingest (drop_out_of_bounds()). - observed
- CTD Derived Products
nitracline_depth1 · median 7 · 152.5 m (5th–95th percentile 1–96.54) - flags
- CTD Derived Products
nitracline_depthcarries no quality code at the release grain; qual_ok keeps all 4,060. - baseline
- A monthly climatology exists for this measurement (the release's climatology table: 1993–2013, dataset × station × the cruise's month × 10 m bin), so the Explorer can draw anomalies against it rather than values.
- derivation
- calcofi4db::profile_threshold_depth(threshold = 1, direction = 'above'): the shallowest sample at or above 1 umol/L, the depth interpolated linearly from the sample above it; a profile already at 1 umol/L in its first sample counts only when that sample is within 20 m of the surface; absent where nitrate never reaches 1 umol/L. The provider's rule (Rasmus Swalethorp 2026-09-24 and his D_NClineDepth.m, questions Q10). calcofi_ctd-derived: on the 1 m bins of the bottle-fitted sensor estimate est_nitrate_sta_corr, final and preliminary_with_bottle casts. calcofi_bottle-derived: on the bottle database's nitrate at the bottle depths of each cast
The familiar scale i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
By month 10 of 12 months
By month i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in
the months the ships sail.
i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in the months the ships sail.
Cite the release, v2026.11.05
Cite the release; each dataset's own citation, licence and DOI are on its page — CTD Derived Products. The Explorer's Share → Cite writes it for the view you make.