feat: Add Density profile plot and cancelable jobs

Adds a Density Plot to the Pipette, it uses the temp and
salinity at node together with surface pressure.

Also fixes the matrix titles for oceanbox/Poseidon#30 and
adds a cancel button as part of oceanbox/Poseidon#41.

.releaserc.yaml

@@ -15,7 +15,7 @@ plugins:
       - "src/Atlantis/src/**.fsproj"
       - "src/Sorcerer/src/**.fsproj"
       - "src/DataAgent/src/**.fsproj"
-      - "src/ServerPack/src/*.fsproj"
+      - "src/ServerPack/src/**.fsproj"
       - "src/Interfaces/**.fsproj"
 - - '@semantic-release/exec'
   - generateNotesCmd: "echo ${nextRelease.version} > VERSION"
@@ -29,7 +29,7 @@ plugins:
       - "src/Atlantis/src/**.fsproj"
       - "src/Sorcerer/src/**.fsproj"
       - "src/DataAgent/src/**.fsproj"
-      - "src/ServerPack/src/*.fsproj"
+      - "src/ServerPack/src/**.fsproj"
       - "src/Interfaces/**.fsproj"
 
 analyzeCommits:

src/Atlantis/src/Client/Lib/Types.fs

@@ -277,6 +277,7 @@ type Prop =
     | Temp
     | Salt
     | Zeta
+    | Dens
     | Speed
     | Conc2D
     | Conc3D
@@ -292,6 +293,7 @@ type Prop =
         | Temp -> "temp"
         | Salt -> "salt"
         | Zeta -> "zeta"
+        | Dens -> "dens"
         | Speed -> "speed"
         | Conc2D -> "concentration2D"
         | Conc3D -> "concentration3D"
@@ -308,6 +310,7 @@ type Prop =
         | Temp -> "Temperature"
         | Salt -> "Salinity"
         | Zeta -> "Tide"
+        | Dens -> "Density (σt(T, S, 0)"
         | Speed -> "Current"
         | Conc2D -> "Concentration2D"
         | Conc3D -> "Concentration3D"
@@ -324,6 +327,7 @@ type Prop =
         | Temp -> 0.0, 15.0
         | Salt -> 27.5, 35.0
         | Zeta -> -1.5, 1.5
+        | Dens -> 20.0, 27.0
         | Speed -> 0.0, 2.0
         | Conc2D -> 0.0, 1.0
         | Conc3D -> 0.0, 1.0
@@ -342,6 +346,7 @@ type Prop =
         | Temp -> -5.0, 45.0
         | Salt -> 0.0, 50.0
         | Zeta -> -5.0, 5.0
+        | Dens -> 15.0, 28.0
         | Speed -> 0.0, 5.0
         | Conc2D -> 0.0, 100.0
         | Conc3D -> 0.0, 100.0
@@ -360,6 +365,7 @@ type Prop =
         | Temp -> 1.0
         | Salt -> 1.0
         | Zeta -> 0.1
+        | Dens -> 0.1
         | Speed -> 0.1
         | Conc2D -> 0.1
         | Conc3D -> 1.0
@@ -377,6 +383,7 @@ type Prop =
         | Temp -> "°C"
         | Salt -> "psu"
         | Zeta -> "m"
+        | Dens -> "kg/m3-1000"
         | Speed -> "m/s"
         | Conc2D -> "1/km2"
         | Conc3D -> "1/km2"
@@ -394,6 +401,7 @@ type Prop =
         | Speed -> elem
         | Temp
         | Salt
+        | Dens
         | Bathy
         | Temp
         | Salt
@@ -414,6 +422,7 @@ type Prop =
         | "zeta" -> Prop.Zeta
         | "temp" -> Prop.Temp
         | "salt" -> Prop.Salt
+        | "dens" -> Prop.Dens
         | "speed" -> Prop.Speed
         | "concentration2D" -> Prop.Conc2D
         | "concentration3D" -> Prop.Conc3D

src/Atlantis/src/Client/Mapster/Inbox.fs

@@ -20,6 +20,7 @@ let inboxDialog
         markAsRead: Guid -> unit
         deleteMessage: Guid -> unit
         postMessage: InboxItem -> unit
+        cancelJob: int -> unit
         unread: int // can flip between +/- N to indicate the need for a reload
         currentDrifters: Map<Guid, SimArchive>
     |}) =
@@ -66,16 +67,32 @@ let inboxDialog
 
     let doDelete _ =
         let table = document.getElementById "inbox-table"
-        let items: InboxItem[] = table?items
+        let selectedSet : Guid JS.Set = table?selectedSet
-        items
+        let items: InboxItem array = table?items
-        |> Array.iter (fun item ->
+        async {
-            if Set.contains item.id selected then
+            let toDelete =
-                arg.deleteMessage item.id)
+                items
-        loadMessages ()
+                |> Array.filter (fun item -> selectedSet.has(item.id))
+                |> Array.map (fun item -> item.id)
+
+            console.debug("Deleting", toDelete.Length, "messages")
+
+            for id in toDelete do
+                arg.deleteMessage id
+
+            // Clear selection immediately
+            selectedSet.clear()
+            setSelected Set.empty
+
+            // Wait a bit for server to process, then reload
+            do! Async.Sleep 200
+            let! mbox = Remoting.inboxApi().getMessages ()
+            table?items <- mbox
+        } |> Async.StartImmediate
 
     let doRead selected _ =
         let table = document.getElementById "inbox-table"
-        let items: InboxItem[] = table?items
+        let items: InboxItem array = table?items
         items
         |> Array.iter (fun item ->
             console.log selected
@@ -221,6 +238,30 @@ let inboxDialog
                 </a>
             """
 
+        let cancelButton =
+            let jobId, canCancel =
+                match item.type' with
+                | MessageType.Progress ->
+                    let progressMsg = decodeProgressMessage item.content
+                    let canCancel = progressMsg.job <> -1
+                    progressMsg.job, canCancel
+                | MessageType.Drifters | MessageType.Job ->
+                    let job = decodeJobMessage item.content
+                    let canCancel = (job.status = JobStatus.Running || job.status = JobStatus.Waiting) && job.job <> -1
+                    job.job, canCancel
+                | _ ->
+                    -1, false
+
+            let doCancelJob _ =
+                if canCancel then arg.cancelJob jobId
+
+            html $"""
+                <sp-action-button  ?disabled={not canCancel} @click={Ev(fun e -> e.stopPropagation(); doCancelJob())}>
+                    <sp-icon-close slot="icon"></sp-icon-close>
+                    <sp-tooltip placement="top" self-managed>Cancel simulation</sp-tooltip>
+                </sp-action-button>
+            """
+
         if item.content = "" then
             html $"""
                 <sp-table-cell></sp-table-cell>
@@ -239,7 +280,10 @@ let inboxDialog
                 <sp-table-cell @click={Ev(chooseItem item)} style="max-width: 120px; align-items: center; display: flex">
                     {formatMsg item.unread inactive (item.created.ToString "dd/MM/yyyy")}
                 </sp-table-cell>
-                <sp-table-cell @click={Ev(_.stopPropagation())} style="max-width: 60px">{downloadButton}</sp-table-cell>
+                <sp-table-cell @click={Ev(_.stopPropagation())} style="max-width: 100px; display: flex; gap: 4px">
+                    {downloadButton}
+                    {cancelButton}
+                </sp-table-cell>
                 """
 
     Hook.useEffectOnce (fun () ->
@@ -285,7 +329,7 @@ let inboxDialog
                         <sp-table-head-cell sortable sort-direction="desc" sort-key="created" style="max-width: 120px">
                             Created
                         </sp-table-head-cell>
-                        <sp-table-head-cell style="max-width: 60px">PDF</sp-table-head-cell>
+                        <sp-table-head-cell style="max-width: 100px">Actions</sp-table-head-cell>
                     </sp-table-head>
                 </sp-table>
 

src/Atlantis/src/Client/Mapster/Mapster.fs

@@ -26,6 +26,7 @@ open Petimeter.Inbox
 open Remoting
 open Sorcerer.Types
 open Utils
+open Atlantis.Shared
 
 let private hmr = HMR.createToken ()
 
@@ -1757,6 +1758,21 @@ let update cmd model =
             }
 
         model, Cmd.OfAsync.perform delete () id
+    | CancelJob jobId ->
+        let cancel () =
+            async {
+                let driftersApi = driftersJobApi ()
+                match! driftersApi.cancelJob jobId with
+                | Ok msg ->
+                    console.log $"[Mapster]: Job {jobId} cancelled : {msg}"
+                    let note = Note.warn msg
+                    return SetNotification note
+                | Error err ->
+                    console.error $"[Mapster]: Failed to cancel job {jobId}: {err}"
+                    let note = Note.error err
+                    return SetNotification note
+            }
+        model, Cmd.OfAsync.perform cancel () id
     | SetIdentity identityOpt ->
         match identityOpt with
         | Some id ->
@@ -2216,6 +2232,7 @@ let MapAppElement () =
         markAsRead = fun id -> Hub.Action.Inbox (Hub.InboxMsg.MarkRead id) |> (HubMsg >> dispatch)
         deleteMessage = fun id -> Hub.Action.Inbox (Hub.InboxMsg.Delete id) |> (HubMsg >> dispatch)
         postMessage = fun _ -> Hub.Action.Inbox (Hub.InboxMsg.Post (testMsg count)) |> (HubMsg >> dispatch)
+        cancelJob = CancelJob >> dispatch
         unread = model.inboxUnread
         currentDrifters = model.availableDrifters
     |}

src/Atlantis/src/Client/Mapster/Model.fs

@@ -98,7 +98,7 @@ type ProbeView =
 
     static member props view : Prop array =
         match view with
-        | DepthProfile -> [| Prop.Temp; Prop.Salt; Prop.Speed |]
+        | DepthProfile -> [| Prop.Temp; Prop.Salt; Prop.Speed; Prop.Dens |]
         | TimeSeries -> [| Prop.Temp; Prop.Salt; Prop.Speed; Prop.Zeta |]
         | RosePlots -> [| Prop.Speed |]
 
@@ -482,6 +482,7 @@ type Msg =
     | SetSimPolicies of DriftersPolicy[]
     | RenameDriftersArchive of System.Guid * string
     | DeleteArchive of System.Guid
+    | CancelJob of int
     | SetPlumeModel of PlumeModel option
     | ShowReleases of bool
 

src/Atlantis/src/Client/Mapster/Navigation.fs

@@ -589,6 +589,9 @@ let private OceanPlotControls model dispatch =
                 <sp-action-button value="{string Prop.Speed}">
                     Speed
                 </sp-action-button>
+                <sp-action-button value="{string Prop.Dens}">
+                    Density
+                </sp-action-button>
             </sp-action-group>
 
             {GraphRangeSlider model dispatch}

src/Atlantis/src/Client/Mapster/Plotly.fs

@@ -656,8 +656,9 @@ module ReactLib =
         let style = {| minHeight = "416px"; width = "100%" |}
         let config = {| responsive = true; editable = false |}
         let layout = {|
-            xaxis = {| side = "top" |}
+            xaxis = {| side = "top"; title = {| text = "Receiver"; standoff = 120 |} |}
-            yaxis = {| autorange = "reversed" |}
+            yaxis = {| autorange = "reversed"; title = {| text = "Sender"; standoff = 120 |} |}
+            margin = {| t = 100; b = 50; l = 100; r = 50 |}
         |}
         let traces = newHeatMap siteNames siteNames weights
 
@@ -718,7 +719,9 @@ module ReactLib =
                 editable = false
             |}
         let layout = {|
-                xaxis = {| side = "top" |}
+                xaxis = {| side = "top"; title = {| text = "Receiver"; standoff = 120 |} |}
+                yaxis = {| title = {| text = "Sender"; standoff = 120 |} |}
+                margin = {| t = 100; b = 50; l = 100; r = 50 |}
             |}
         let traces = newCageHeatMap groupNames' cageNames weights'
 
@@ -731,6 +734,7 @@ module ReactLib =
              />
         """
 
+
 // NOTE(simkir): !! These cannot be partially applied! Or, the exposing Component must be curried, so not take any
 // arguments.
 //

src/Atlantis/src/Client/Mapster/Plots/DepthPlots.fs

@@ -18,9 +18,13 @@ let private fetchPropData (archiveId: System.Guid) (frame: FrameIdx) (gridIdx: G
             match prop with
             | Prop.Temp -> fvcom.Node.GetTemp archiveId frame
             | Prop.Salt -> fvcom.Node.GetSalinity archiveId frame
+            | Prop.Dens -> fvcom.Node.GetDensity archiveId frame
             | Prop.Speed -> fvcom.Element.GetSpeed archiveId frame
             | _ -> fun _ -> async.Return [||]
+        
+        console.debug("[DepthPlots] Fetching %s data for archive %s, frame %d, idx %d", string prop, string archiveId, frame, idx)
         let! res = fetch idx |> Async.StartAsPromise
+        console.debug("[DepthPlots] Received %s data: length=%d, data=%o", string prop, res.Length, res)
 
         return res
     }
@@ -322,7 +326,10 @@ let View
         fun updatedStats ->
             console.debug ("[DepthPlots] Stats changed %o", updatedStats)
             if updatedStats.propType = Undefined then
-                console.warn "[DepthPlots] Stats prop type is Undefined!"
+                if probeProp = Atlantis.Types.Prop.Dens then
+                    console.debug "[DepthPlots] Density selected - statistics not available, showing instant data only"
+                else
+                    console.warn "[DepthPlots] Stats prop type is Undefined!"
             else
                 console.debug ("[DepthPlots] Stats prop type is %s", string updatedStats.propType)
                 do FetchMetrics updatedStats |> dispatch

src/Atlantis/src/Server/Api.fs

@@ -445,6 +445,22 @@ module Handlers =
         }
         |> Async.AwaitTask
 
+    let private cancelJob (ctx: HttpContext) jobId =
+        let user = getUserName ctx
+        Log.Information ("User {username} cancels job {}", user, jobId)
+        let actorId = ActorId user
+
+        task {
+            try
+                let proxy = ActorProxy.Create<IDriftersActor>(actorId, "DriftersActor")
+                return! proxy.Cancel jobId
+            with exn ->
+                Log.Error $"cancelJob: {exn.Message}"
+                Log.Verbose $"cancelJob: %A{exn}"
+                return Error exn.Message
+        }
+        |> Async.AwaitTask
+
     let driftersApi (ctx: HttpContext) : Api.Drifters = {
         startDrifters = runDrifters ctx
         startPostdrift = runPostdrift ctx
@@ -455,6 +471,7 @@ module Handlers =
         getDriftersInput = getDriftersInput ctx
         renameArchive = renameArchive ctx
         retireArchive = retireArchive ctx
+        cancelJob = cancelJob ctx
     }
 
     let inboxApi (ctx: HttpContext) : Api.Inbox = {

src/Atlantis/src/Server/Hipster/DriftersActor.fs

@@ -246,7 +246,7 @@ type DriftersActor(host: ActorHost, slurm: SlurmClient, settings: Common.Setting
     //     }
 
     interface IJobActor with
-        member this.Cancel() = this.cancel ()
+        member this.Cancel(jobId) = this.cancel  jobId
         member this.HandleJobEvent(job) = this.handleJobEvent job
         member this.Remove(jobid) = this.remove jobid
         member this.RemoveById(aid: Guid) = this.removeById aid

src/Atlantis/src/Server/Hipster/JobActor.fs

@@ -156,9 +156,32 @@ type JobActor(host: ActorHost, slurm: SlurmClient, settings: Common.Settings) =
         else
             Task.FromResult ()
 
-    member this.cancel() =
+    member this.cancel(jobId: int) =
-        Log.Debug $"cancel (not implemented yet): {this.myId}"
+        Log.Debug $"[JobActor.Cancel]: Cancel job %i{jobId}: %s{this.myId}"
-        task { return true }
+        task {
+            try
+                if this.jobs.ContainsKey jobId then
+                    let! cancelled = slurm.CancelJob jobId
+                    if cancelled then
+                        let updatedJob = { this.jobs[jobId] with status = JobStatus.Failed }
+                        this.jobs[jobId] <- updatedJob
+                        do! this.StateManager.SetStateAsync (this.jobsKey, this.jobs)
+
+                        // Publish cancellation to pubsub so clients are immediately notified
+                        do! client.PublishEventAsync<JobInfo> ("pubsub", "hipster", updatedJob)
+
+                        // Post status to inbox when job is cancelled successfully
+                        do! this.postStatus MessageType.Job updatedJob
+
+                        return Ok "Simulation cancelled"
+                    else
+                        return Error "Failed to cancel job"
+                else
+                    return Error "Job not found"
+            with exn ->
+                Log.Error $"[JobActor.cancel]: Cancel job {jobId} failed: {exn.Message}"
+                return Error exn.Message
+        }
 
     member this.handleJobEvent(job: SlurmJobStatusMsg) =
         let job' =
@@ -182,26 +205,31 @@ type JobActor(host: ActorHost, slurm: SlurmClient, settings: Common.Settings) =
 
         task {
             match job' with
+            | None ->
+                Log.Debug $"[JobActor.handleJobEvent] No job found with id: %d{job.jobId}"
+                Log.Debug $"[JobActor.handleJobEvent] jobs: %A{this.jobs}"
+                return ()
             | Some j ->
                 match job.messageType with
                 | "progress" -> do! this.postProgress job
                 | _ ->
                     let status = LanguagePrimitives.EnumOfValue (int job.content)
-                    let j' = { j with status = status }
-                    do! update j'
 
-                    let jobType = job.jobType |> inboxMessageTypeFromString
+                    // Don't update if job is already cancelled (Failed)
-
+                    if j.status = JobStatus.Failed then
-                    if status = JobStatus.Completed then
+                        Log.Debug $"[JobActor.handleJobEvent] Ignoring status update for cancelled job {job.jobId}: current={j.status}, new={status}"
-                        // Delay for Atlantis to update on job completion
-                        System.Threading.Thread.Sleep 1000
-                        do! this.postStatus jobType j'
                     else
-                        do! this.postStatus MessageType.Job j'
+                        let j' = { j with status = status }
-            | None ->
+                        do! update j'
-                Log.Debug $"[JobActor.handleJobEvent] No job found with id: %d{job.jobId}"
+
-                Log.Debug $"[JobActor.handleJobEvent] jobs: %A{this.jobs}"
+                        let jobType = job.jobType |> inboxMessageTypeFromString
-                return ()
+
+                        if status = JobStatus.Completed then
+                            // Delay for Atlantis to update on job completion
+                            System.Threading.Thread.Sleep 1000
+                            do! this.postStatus jobType j'
+                        else
+                            do! this.postStatus MessageType.Job j'
         }
 
     member this.remove(jobid) =

src/Atlantis/src/Server/Hipster/PlumeActor.fs

@@ -71,7 +71,7 @@ type PlumeActor(host: ActorHost, slurm: SlurmClient, settings: Common.Settings,
             submitJob ()
 
     interface IJobActor with
-        member this.Cancel() = this.cancel ()
+        member this.Cancel(jobId) = this.cancel jobId
         member this.HandleJobEvent(job) = this.handleJobEvent job
         member this.Remove(jobid) = this.remove jobid
         member this.RemoveById(aid: Guid) = this.removeById aid

src/Atlantis/src/Server/Hipster/Slurm.fs

@@ -189,4 +189,17 @@ type SlurmClient(client: HttpClient, settings: ISlurmClientSettings) =
             match Decode.Auto.fromString<SlurmJobsResponse> rsp' with
             | Ok job -> return Array.tryHead job.jobs |> Option.map (fun q -> getJobStatus q.job_state)
             | Error _ -> return None
+        }
+
+    member this.CancelJob(jobId: int) =
+        task {
+            try
+                // Cancel or signal job
+                // https://slurm.schedmd.com/rest_api.html#slurmV0044DeleteJob
+                let! rsp = client.DeleteAsync $"job/%i{jobId}"
+                // Returns 200 no succesful cancel
+                return rsp.IsSuccessStatusCode
+            with exn ->
+                Log.Error $"Cancel job %i{jobId} failed: %s{exn.Message}"
+                return false
         }

src/Interfaces/Atlantis/Api.fs

@@ -57,6 +57,7 @@ module Api =
             getDriftersInput: Guid -> Async<Result<DriftersInput option, string>>
             renameArchive: Guid -> string -> Async<Result<unit, string>>
             retireArchive: Guid -> Async<Result<unit, string>>
+            cancelJob: int -> Async<Result<string, string>>
         }
 
     type Inbox =

src/Interfaces/Hipster/Actors.fs

@@ -50,7 +50,6 @@ type PostdriftJob = {
 
 type IJobActor =
     inherit IActor
-    abstract Cancel: unit: unit -> Task<bool>
     abstract Remove: job: int -> Task<bool>
     abstract RemoveById: aid: Guid -> Task<bool>
     abstract Clear: unit: unit -> Task
@@ -59,6 +58,7 @@ type IJobActor =
     abstract GetActiveJobs: aid: Guid -> Task<JobInfo[]>
     abstract GetFenceRadius: unit: unit -> Task<float>
     abstract CheckFence: aid: Guid * pos: (float * float) list -> Task<bool>
+    abstract Cancel: job: int -> Task<Result<string, string>>
 
 type IDriftersActor =
     inherit IJobActor

src/Interfaces/Sorcerer/Api.fs

@@ -39,6 +39,7 @@ module Api =
             GetBathymetry: Guid -> NodeIdx -> Async<single>
             GetTemp: Guid -> FrameIdx -> NodeIdx -> Async<single array>
             GetSalinity: Guid -> FrameIdx -> NodeIdx -> Async<single array>
+            GetDensity: Guid -> FrameIdx -> NodeIdx -> Async<single array>
         }
 
         type Element = {

src/Sorcerer/src/Server/Api.fs

@@ -446,6 +446,15 @@ module Fvcom =
                             Fvcom.salinityAtNode aid t n
                             |> Result.defaultValue Array.empty
                     }
+            GetDensity =
+                fun aid t n ->
+                    async {
+                        let logData = {| aid = aid; n = n |}
+                        use _ = observer.trace ("GetDensity", "{@log_data}", logData)
+                        return
+                            Fvcom.densityAtNode aid t n
+                            |> Result.defaultValue Array.empty
+                    }
         }
 
     let elementApi (ctx: HttpContext) : Fvcom.Element =

src/Sorcerer/src/Server/Fvcom.fs

@@ -214,6 +214,96 @@ let private queryGridIndexCache (aid: Guid) (grid: ExtendedGrid) =
     }
     |> Async.Start
 
+/// Compute density of seawater from salinity, temperature, and pressure
+let private dens (temp: float) (salt: float) (pres: float) =
+    // From Bjørn Aadlandsvik https://github.com/bjornaa/seawater/blob/master/seawater/density.py
+
+    /// Density of seawater at zero pressure
+    let dens0 (salt: float) (temp: float) =
+        // --- Define constants ---
+        let a0 = 999.842594
+        let a1 = 6.793952e-2
+        let a2 = -9.095290e-3
+        let a3 = 1.001685e-4
+        let a4 = -1.120083e-6
+        let a5 = 6.536332e-9
+
+        let b0 = 8.24493e-1
+        let b1 = -4.0899e-3
+        let b2 = 7.6438e-5
+        let b3 = -8.2467e-7
+        let b4 = 5.3875e-9
+
+        let c0 = -5.72466e-3
+        let c1 = 1.0227e-4
+        let c2 = -1.6546e-6
+
+        let d0 = 4.8314e-4
+
+        // --- Computations ---
+        // Density of pure water
+        let SMOW = a0 + (a1 + (a2 + (a3 + (a4 + a5 * temp) * temp) * temp) * temp) * temp
+
+        // More temperature polynomials
+        let RB = b0 + (b1 + (b2 + (b3 + b4 * temp) * temp) * temp) * temp
+        let RC = c0 + (c1 + c2 * temp) * temp
+
+        SMOW + RB * salt + RC * (salt ** 1.5) + d0 * salt * salt
+
+    /// Secant bulk modulus
+    let seck salt temp pres =
+        // --- Pure water terms ---
+        let h0 = 3.239908
+        let h1 = 1.43713e-3
+        let h2 = 1.16092e-4
+        let h3 = -5.77905e-7
+        let AW = h0 + (h1 + (h2 + h3 * temp) * temp) * temp
+
+        let k0 = 8.50935e-5
+        let k1 = -6.12293e-6
+        let k2 = 5.2787e-8
+        let BW = k0 + (k1 + k2 * temp) * temp
+
+        let e0 = 19652.21
+        let e1 = 148.4206
+        let e2 = -2.327105
+        let e3 = 1.360477e-2
+        let e4 = -5.155288e-5
+        let KW = e0 + (e1 + (e2 + (e3 + e4 * temp) * temp) * temp) * temp
+
+        // --- Seawater, P = 0 ---
+        let SR = salt ** 0.5
+
+        let i0 = 2.2838e-3
+        let i1 = -1.0981e-5
+        let i2 = -1.6078e-6
+        let j0 = 1.91075e-4
+        let A = AW + (i0 + (i1 + i2 * temp) * temp + j0 * SR) * salt
+
+        let f0 = 54.6746
+        let f1 = -0.603459
+        let f2 = 1.09987e-2
+        let f3 = -6.1670e-5
+        let g0 = 7.944e-2
+        let g1 = 1.6483e-2
+        let g2 = -5.3009e-4
+        let K0 =
+            KW
+            + (f0 + (f1 + (f2 + f3 * temp) * temp) * temp + (g0 + (g1 + g2 * temp) * temp) * SR)
+              * salt
+
+        // --- General expression ---
+        let m0 = -9.9348e-7
+        let m1 = 2.0816e-8
+        let m2 = 9.1697e-10
+        let B = BW + (m0 + (m1 + m2 * temp) * temp) * salt
+
+        K0 + (A + B * pres) * pres
+
+    // Convert to bar
+    let pres = 0.1 * pres
+    (dens0 salt temp) / (1.0 - pres / seck salt temp pres)
+
 let nLayers (aid: Guid) =
     let f ds _ = Fvcom.getNumSiglay ds
     dataAgent.eval (f, aid)
@@ -472,6 +562,26 @@ let zetaAtNode aid t n =
     let f ds t = Fvcom.Singular.readZeta ds n t
     dataAgent.eval (f, aid, t)
 
+let densityAtNode aid t n =
+    monad {
+        let! temp = tempAtNode aid t n
+        let! salt = salinityAtNode aid t n
+        let! h = bathymetryAtNode aid n
+        let! zeta = zetaAtNode aid t n
+        let! siglay = siglay aid n
+
+        return
+            Array.map3 (fun t_val s_val sigma ->
+                let depth = abs (sigma * h + zeta) |> float
+                let t_val = float t_val
+                let s_val = float s_val
+                // NOTE: Pressure set to surface pressure which is
+                // approx 0 using σ_t(T, S, 0)
+                let pres = 0
+                (dens t_val s_val pres - 1000.) |> single
+            ) temp salt siglay
+    }
+
 let getDepthsAtNode aid node =
     monad {
         let! h = bathymetryAtNode aid node