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SCIENCE · INVESTIGATE AND EXPLAIN

Read a recorded ocean profile

Audit eight selected actual Argo levels and compare properties without inventing movement.

Learning outcome: Report a reproducible profile difference with provenance, units and unavailable metadata.

Starting recap

INCOIS WMO 1900121 cycle 1 is an ascending 2002 profile; adjusted pressure is not depth.

All lessons are open directly. Your saved experiments remain when you leave and return.

Try

From 96.5 to 206.7 dbar, temperature changes by -7.351 degrees C and practical salinity by -0.01623.

Open the experiment

Predict

Will both recorded properties decrease across the selected pressure interval?

Experiment

Copy two actual rows, subtract in a stated order and audit quality flags and unavailable errors.

Compare temperature and salinity contributions to density

Illustrative parcel-density comparison · qualitative circulation mechanisms · Original illustrative relation at one common reference pressure: density = 1027 − 0.2(T − 10) + 0.8(S − 35) kg/m³. Lower reference has T=10°C and S=35. S is a dimensionless practical-salinity-like teaching input, not an exact g/kg value. Coefficients are 0.2 kg/m³ per °C and 0.8 kg/m³ per unit of salinity input. Salinity values and coefficients are teaching assumptions, not a validated seawater equation of state or measured profile. Stable/unstable/neutral refers only to this density ordering. No pressure/depth effects, circulation speed, mixing timescale or transport is inferred.

Reset keeps your prediction, captures and practice history.

Separate the effects of temperature and salinity

Start with two hypothetical parcels compared at the same reference pressure. The lower parcel stays at 10°C with salinity input 35 and reference density 1027 kg/m³. Change the upper parcel. Predict which contribution increases its density before inspecting the calculation. The model’s numbers are teaching assumptions, not measured seawater properties or a validated equation of state.

Illustrative upper-parcel calculation, all density terms in kg/m³
TermCalculationValue
Reference densityLower parcel: 10°C, salinity 351027.00
Temperature contribution−0.2 × (10 − 10)0.00
Salinity contribution+0.8 × (35 − 35)0.00
Upper density1027 + temperature term + salinity term1027.00
Upper minus lower1027.00 − 1027.000.00

The salinity input is a dimensionless teaching scale resembling practical salinity. It is not an exact grams-per-kilogram conversion. Here −0.2 has units kg/m³ per °C and +0.8 has units kg/m³ per salinity-input unit. Actual seawater density depends nonlinearly on temperature, composition and pressure; this rule is used only for these hypothetical comparisons.

Contributions relative to the lower reference (kg/m³), fixed scale −2 to +2-2-1012Temperature0.00Salinity0.00Combined0.00Left: lighter than reference · right: denser than reference

A tendency, not a simulated current

Upper: 10°C · salinity 35Density 1027.00 kg/m³Lower: 10°C · salinity 35Density 1027.00 kg/m³Equal model densitiesneutral arrangementNo speed calculatedNo final depth calculatedSame reference pressure; no imposed stirring or wind in this two-parcel comparison.

Equal modeled densities give no density contrast in this comparison. Equality is not proof that real seawater is perfectly neutral; the illustrative formula omits additional physics.

Try a competing-effects case and check it

Predict the result at 14°C and salinity 36. Warming contributes −0.80 kg/m³ while the salinity increase contributes +0.80 kg/m³. They cancel in this rule, leaving 1027 kg/m³. At 16°C and the same salinity, the temperature term becomes −1.20, so the net is −0.40: the upper parcel is lighter. “Saltier” alone does not settle the density comparison when temperature also changes.

Try the reverse competition at 6°C and salinity 34. Both contributions again cancel. At 4°C and salinity 34, the cooling term +1.20 exceeds the freshening term −0.80, leaving the upper parcel 0.40 kg/m³ denser. Explain why the word “cold” alone still does not establish a real current’s direction.

Surface transport and deep circulation have different evidence needs

Wind transfers momentum to the sea surface. Rotation deflects moving water; basin boundaries and pressure gradients help shape currents. Wind-driven transport can redistribute heat without requiring every warm parcel to sink. Surface waves and currents are different: a passing wave pattern is not a direct measurement of sustained water transport.

Northern Hemisphere: plan viewLandOcean · westN ↑Wind southNet transport offshoreSeparate vertical sectionLandSurface exportDeeper replacement ↑Ideal net transport, not every layer’s velocity; local conditions can change this pattern.

In this idealized Northern Hemisphere example, southward wind along a north–south coast gives depth-integrated Ekman transport to its right, offshore to the west. Deeper water can replace exported near-surface water. The ideal transport direction is not a universal angle for every current or every depth; coasts, duration, friction and stratification matter. Mirror the hemisphere and re-evaluate the direction rather than memorizing this drawing.

Check what the density rule cannot establish

Cooling and increased salinity can favor higher density, but a density contrast alone does not map a global route or supply a flow rate. Deep circulation involves buoyancy changes, winds, mixing, pressure gradients and basin geometry. A conveyor diagram summarizes connected transport; actual parcels do not follow a single closed loop with a universal travel time. To test a transport claim, seek measurements of motion and location over time, not only temperature or salinity.

Primary background: NOAA currents and rotation; NOAA temperature, salinity and deep circulation; NOAA coastal upwelling. The original numerical rule and diagrams above are teaching constructions, separate from measured ocean records.

One observed ocean profile, eight selected levels

This fixed INCOIS Argo record is separate from the illustrative density controls. Float WMO 1900121, cycle 1, ascended in the Indian Ocean at -9.857° latitude, 55.953° longitude. The profile timestamp is 2002-11-11 09:20:28 UTC; it does not mean every level was sampled simultaneously.

Predict before checking: between 96.5 and 206.7 dbar, do temperature and salinity change in the same direction? Use the table to calculate both changes. Then decide whether either change tells you how fast water travels horizontally.

In-situ temperature (°C)01020300500100015002000Pressure (dbar), increasing ↓Points are selected observations; lines only guide the eye between them.Fixed axes; no pressure-to-depth conversion or current velocity is calculated.
Practical salinity (dimensionless; source label PSU)34.53535.50500100015002000Pressure (dbar), increasing ↓Points are selected observations; lines only guide the eye between them.Fixed salinity axis starts at 34.5, not zero. No density is calculated.
Adjusted values from one ascending profile; original source row indices retained
Source row (zero-based)Pressure dbarIn-situ temperature °CPractical salinityAdjusted QC: pressure / T / S
02.627.38835.378061 / 1 / 1
946.427.18135.370891 / 1 / 1
1496.521.16935.136421 / 1 / 1
22206.713.81835.120191 / 1 / 1
29496.48.95334.788601 / 1 / 1
34996.45.86434.770571 / 1 / 1
391496.43.74534.743551 / 1 / 1
441996.02.58834.737431 / 1 / 1

The eight selected points omit local structure. Original source row 12, not plotted here, reports 76.3 dbar, 25.461 °C and practical salinity 35.40648—higher than the uppermost selected salinity 35.37806. The complete profile therefore does not show a monotonic salinity decrease. All 45 source rows are retained for audit.

Check the profile comparison and inference

At 96.5→206.7 dbar, temperature changes by 13.818 − 21.169 = −7.351 °C and practical salinity by 35.12019 − 35.13642 = −0.01623. Both decrease between those levels. This is a comparison within an ascending profile, not a climate trend, stationary time series or measured current speed. We selected eight of 45 actual levels; the intervening rows remain in the frozen source record.

The uppermost selected temperature is 27.388 °C, outside the illustrative density lab's range. More fundamentally, these observations occur at unequal pressures. Do not put them into the toy density rule to infer real stability: an appropriate common-reference oceanographic calculation would be needed. A density contrast alone would still not determine current velocity or transport.

Transfer: compare 496.4 and 996.4 dbar using the table. What additional measurement would establish water motion? A suitable displacement/time record with depth context or a direct velocity measurement would help; volume transport also requires a cross-section.

Inspect source fields, quality and missing metadata

The displayed values use PRES_ADJUSTED, TEMP_ADJUSTED and PSAL_ADJUSTED. At source row 0, pressure changes from 5.5 dbar raw to 2.6 dbar adjusted, and salinity from 35.377 to 35.37806. Those are processing versions of one observation, not a measured change through time. Quality flag 1 means good data. The timestamp has QC 1; good quality is not zero uncertainty.

This provider does not expose DATA_MODE, position quality or adjusted-error fields. They remain unavailable, not zero. We do not assert delayed-mode processing or invent error bars. The reported decimal places do not establish accuracy. The source calls practical salinity “PSU”; it is dimensionless and is not directly grams of salt per kilogram. Pressure in dbar is not measured depth in metres.

Exact INCOIS profile query · Provider units and metadata · Argo field and quality guidance · Argo dataset citation.

Data were collected and made freely available by International Argo and contributing national programs, and distributed here by INCOIS. Frozen on 2026-10-26; the local snapshot retains the source's free-use and redistribution terms. This lesson needs no live request. One profile does not describe a permanent global conveyor or the whole Indian Ocean.

Inspect all 45 original source rows

This is the exact frozen CSV response: field names, units row and every original level. Adjusted and raw values are distinct columns.

PLATFORM_NUMBER,CYCLE_NUMBER,DIRECTION,time,JULD_QC,latitude,longitude,PRES,PRES_QC,PRES_ADJUSTED,PRES_ADJUSTED_QC,TEMP,TEMP_QC,TEMP_ADJUSTED,TEMP_ADJUSTED_QC,PSAL,PSAL_QC,PSAL_ADJUSTED,PSAL_ADJUSTED_QC
,,,UTC,,degrees_north,degrees_east,decibar,,decibar,,degree_Celsius,,degree_Celsius,,PSU,,PSU,
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,5.5,1,2.6,1,27.388,1,27.388,1,35.377,1,35.37806,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,9.4,1,6.5,1,27.375,1,27.375,1,35.377,1,35.37834,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,14.3,1,11.4,1,27.302,1,27.302,1,35.376,1,35.37714,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,18.9,1,16.0,1,27.268,1,27.268,1,35.374,1,35.37504,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,23.9,1,21.0,1,27.247,1,27.247,1,35.373,1,35.37396,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,29.0,1,26.1,1,27.243,1,27.243,1,35.374,1,35.37495,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,34.4,1,31.5,1,27.239,1,27.239,1,35.375,1,35.37597,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,39.2,1,36.3,1,27.231,1,27.231,1,35.374,1,35.37496,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,43.9,1,41.0,1,27.227,1,27.227,1,35.372,1,35.37321,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,49.3,1,46.4,1,27.181,1,27.181,1,35.369,1,35.37089,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,59.4,1,56.5,1,26.874,1,26.874,1,35.401,1,35.40385,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,69.6,1,66.7,1,26.231,1,26.231,1,35.401,1,35.40441,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,79.2,1,76.3,1,25.461,1,25.461,1,35.401,1,35.40648,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,89.7,1,86.8,1,23.931,1,23.931,1,35.304,1,35.31376,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,99.4,1,96.5,1,21.169,1,21.169,1,35.131,1,35.13642,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,109.3,1,106.4,1,19.968,1,19.968,1,35.104,1,35.10599,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,119.6,1,116.7,1,19.708,1,19.708,1,35.101,1,35.10602,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,129.3,1,126.4,1,18.546,1,18.546,1,35.108,1,35.11077,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,138.9,1,136.0,1,18.069,1,18.069,1,35.102,1,35.10677,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,149.4,1,146.5,1,16.922,1,16.922,1,35.084,1,35.0865,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,168.9,1,166.0,1,16.142,1,16.142,1,35.094,1,35.09767,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,189.2,1,186.3,1,14.663,1,14.663,1,35.085,1,35.08771,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,209.6,1,206.7,1,13.818,1,13.818,1,35.118,1,35.12019,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,229.5,1,226.6,1,13.267,1,13.267,1,35.103,1,35.10528,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,248.8,1,245.9,1,12.71,1,12.71,1,35.092,1,35.09405,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,299.0,1,296.1,1,11.565,1,11.565,1,34.981,1,34.9829,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,349.4,1,346.5,1,10.741,1,10.741,1,34.915,1,34.91695,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,399.2,1,396.3,1,9.875,1,9.875,1,34.836,1,34.83772,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,449.4,1,446.5,1,9.376,1,9.376,1,34.799,1,34.80067,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,499.3,1,496.4,1,8.953,1,8.953,1,34.787,1,34.7886,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,599.1,1,596.2,1,8.293,1,8.293,1,34.767,1,34.76867,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,699.5,1,696.6,1,7.497,1,7.497,1,34.774,1,34.77563,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,799.6,1,796.7,1,6.846,1,6.846,1,34.774,1,34.77559,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,898.8,1,895.9,1,6.345,1,6.345,1,34.77,1,34.77159,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,999.3,1,996.4,1,5.864,1,5.864,1,34.769,1,34.77057,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1099.4,1,1096.5,1,5.476,1,5.476,1,34.769,1,34.77061,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1199.4,1,1196.5,1,4.971,1,4.971,1,34.765,1,34.76662,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1299.1,1,1296.2,1,4.48,1,4.48,1,34.76,1,34.76163,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1399.6,1,1396.7,1,3.991,1,3.991,1,34.746,1,34.74754,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1499.3,1,1496.4,1,3.745,1,3.745,1,34.742,1,34.74355,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1599.1,1,1596.2,1,3.476,1,3.476,1,34.739,1,34.74052,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1698.9,1,1696.0,1,3.264,1,3.264,1,34.74,1,34.74154,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1799.5,1,1796.6,1,3.017,1,3.017,1,34.738,1,34.73951,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1899.0,1,1896.1,1,2.832,1,2.832,1,34.737,1,34.73853,1
1900121,1,A,2002-11-11T09:20:28Z,1,-9.857,55.953,1998.9,1,1996.0,1,2.588,1,2.588,1,34.736,1,34.73743,1

Upper illustrative density 1027.00 kg/m³; lower 1027.00 kg/m³; upper minus lower 0.00 kg/m³. neutral density ordering.

The parcels have equal illustrative density within arithmetic tolerance: neutral density ordering in this restricted comparison. Temperature contributes 0.00 and salinity 0.00 kg/m³ relative to the reference. These assumed coefficients are not a validated seawater equation of state; no observed profile, current speed or transport is calculated.

Captures preserve the hypothetical upper parcel temperature and salinity. Replay recalculates the illustrative density ordering; it does not measure seawater, calculate current speed or change recorded ocean observations.

Understand

Start with the record, not a circulation story

Open the fixed observed-profile panel and identify its source before interpreting either graph. This is an actual Argo record distributed by the Indian National Centre for Ocean Information Services (INCOIS), not output generated by the temperature and salinity controls. Moving those controls changes the illustrative two-layer experiment; it does not rewrite the observations.

Copy this profile identity into a paper ledger: float WMO 1900121, cycle 1, ascending, 11 November 2002 at 09:20:28 UTC, latitude −9.857° and longitude 55.953°. A negative latitude indicates south of the equator. The coordinates locate the profile; they do not identify a measured current direction. The timestamp identifies this historical record, not present conditions at that location.

Decode axes and provenance

The panel selects eight actual adjusted levels from the source’s 45 rows. It preserves their pressures rather than interpolating to convenient round numbers. Temperature is in-situ temperature in degrees Celsius. Pressure is in decibars, abbreviated dbar, and increases downward in the plots. Pressure is not depth in meters; this activity performs no pressure-to-depth conversion.

Practical salinity is dimensionless. The provider’s label PSU is retained as source metadata, but it is not an instruction to convert each number directly to grams per kilogram. The salinity axis deliberately shows a narrow range with a nonzero lower bound. Read the numbers before deciding that a visually large separation represents a large fractional change.

The INCOIS data access page supplies the original variables. Our offline snapshot retains the complete returned table, selection, retrieval date and source metadata. Lines between the eight plotted points guide the eye; they are not extra measurements. The selected salinities decrease, but the full profile is not monotonic: an omitted level at 76.3 dbar has salinity 35.40648, above the first selected value 35.37806. Selection can hide a local maximum; do not extend a pattern in eight rows to every source row. In particular, the first selected pressure is 2.6 dbar, not a sampled zero-pressure surface.

Make a comparison you can reproduce

Predict the signs of the temperature and salinity differences between 96.5 and 206.7 dbar. Then copy both rows, keeping the order fixed: higher-pressure value minus lower-pressure value. Temperature changes from 21.169 to 13.818 °C, giving 13.818 − 21.169 = −7.351 °C. Practical salinity changes from 35.13642 to 35.12019, giving −0.01623.

Write the result as a comparison within this profile. It does not say that one stationary location cooled by 7.351 °C over years, or that the same parcel changed by this amount while moving. A vertical sampling sequence and a long-term time series answer different questions. Nor does the temperature difference provide velocity: dividing it by a pressure difference would produce temperature change per pressure, not meters per second.

Audit quality without inventing precision

All eight selected adjusted pressure, temperature and salinity values have QC flag 1; the time flag is also 1. Argo’s file-use guidance explains the flags and associated error information. Flag 1 means good data under the applicable checks, not perfectly exact measurements.

This provider table does not expose data mode, position QC or adjusted-error fields. Mark those unavailable. Do not infer delayed-mode processing merely because a variable says adjusted, or assign an uncertainty from the last printed decimal. At the first row, raw pressure is 5.5 dbar and adjusted pressure is 2.6 dbar: their difference describes two versions of one observation, not a later physical pressure change.

Do not insert this profile into the teaching density equation. Several temperatures exceed its selectable range, pressures differ, and it is not a validated seawater equation. A suitable oceanographic method and its reference-pressure conventions would be needed for a physical density analysis.

Transfer: compare a different interval

Use 496.4 and 996.4 dbar. Their temperatures are 8.953 and 5.864 °C; practical salinities are 34.78860 and 34.77057. Calculate both differences, then state whether they establish current speed or a climate trend. Write your answer before opening the public explanation; this practice does not independently certify mastery.

Check the ocean-observations transfer

Higher-pressure minus lower-pressure temperature is −3.089 °C; practical-salinity difference is −0.01803. Both decrease across these selected levels. Neither difference measures current speed or establishes a long-term trend. Retain profile identity, adjusted variables, pressure units and unavailable error information in the report.

Apply

An adjusted value with QC flag 1 establishes:

Public practice checks a specific claim. It does not establish independent mastery.

Explain why the fixed observations do not change with the controls or establish a current speed.

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

Skipping retains experiments and awards no mastery.

Previous: Interpret a two-layer density comparisonNext: Follow water and energy without a conveyor shortcut
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