GP17inthecontextoftheglobalsurvey

GP17

SeaWiFS-AnnualMeanChlorophyll

https://earthobservatory.nasa.gov/IOTD/view.php?id=4097

GP17-LowestmodeldustfluxintheSouthernOcean

AresurfaceFeconcentrationscorrelatedwithmodern(model)dustflux?TestbycomparingGP17withothersections(pink).DustmodelofAlbani,Mahowaldetal.,2014

MotivationfortheGP17Section1) Ultra-oligotrophic South Pacific Gyre

Low dust, productivity, particles – impact on scavenging? Record deep DCM – impact on colloid cycling?

2) Southern Ocean regulation of global biological pump efficiency Upwelling hot spots – source of Fe? Dust vs. upwelling sources of micronutrients SE Pacific low biomass – control by Fe, MLD, other?

3) Dispersal of continental sources of micronutrients Basal melt Subglacial meltwater runoff Extent of signal

4) Outflow of Fe carried by Pacific Deep Water Large Fe sources from margins and ridges How much reaches Southern Ocean? Stabilization of Fe (and other TEIs) by ligands

P16FeandNitrate

Fe and N have similar distributions in the north, dissimilar in the south. Causes & consequences for ecosystems? Complements of Chris Measures & Mariko Hatta

P16FeandAl

SPSG: High Al coincides with low Fe – ultra-low scavenging intensity? Complements of Chris Measures & Mariko Hatta

P16FeandAl

Low Al in the Southern Ocean – diatom scavenging? Complements of Chris Measures & Mariko Hatta

GP17TentativeCruiseTrack

NBP1702 with Orsi climatological fronts

TempandSalinity

UCDW

SAF?

AlittletrickytosaywhatthenorthwardextentofthesubsurfaceTminimumis–seemstogomuchfurthernorththanwhatyou’dusuallycalltheAPF

DatafromRebeccaRobinson&MarkBrzezinski

UCDWLCDW?

ObviousO2minimumassociatedwithUCDW

Oxygen

DatafromRebeccaRobinson&MarkBrzezinski

dSiandbSi

ConsistencybetweenSiOH4drawdownat61-63ºSwithhighestbSivaluesthere–regionofmostintensediatomproductivity.HighSiOH4southof63S(incompleteutilizationofnutrientssuppliedbydeepwintermixing?),lowSiOH4inwaterscarriednorthof~61SbyEkmantransport

DatafromRebeccaRobinson&MarkBrzezinski

PicturefromSi*isthesame–surfaceSi*valuesarelowestat62S,higherbutstillnegativeat63S,andpositiveat64S.

Note500mdepthscale

DatafromRebeccaRobinson&MarkBrzezinski

Si*=[Si]–[NO3]

PicturefromSi*isthesame–surfaceSi*valuesarelowestat62S,higherbutstillnegativeat63S,andpositiveat64S.

Note500mdepthscale

DatafromRebeccaRobinson&MarkBrzezinski

Si*=[Si]–[NO3]

Entire SH nutrient source has negative Si* because of processes occurring here

WhatisthesourceofdFetosupportthisdiatomgrowth?

DatafromRebeccaRobinson&MarkBrzezinski

Si*=[Si]–[NO3]

Entire SH nutrient source has negative Si* because of processes occurring here

NutrientdataisconsistentwithlocationsofmostintenseParemovalanddecouplingalongneutraldensitysurfaces.

LowestsurfacePafrom63S-61S

Strongestisopycnal231Pagradientsat/belowyn=27.6openupbetweenstation7(62S)andstation5(63S)

NutrientdataisconsistentwithlocationsofmostintenseParemovalanddecouplingalongneutraldensitysurfaces.

LowestsurfacePafrom63S-61S

Strongestisopycnal231Pagradientsat/belowyn=27.6openupbetweenstation7(62S)andstation5(63S)

WhatotherTEIsarescavengedbyopalaswell?Al?

Samplingresolution

Standard GEOTRACES sampling at 5° resolution could miss the zone of maximum diatom productivity Higher resolution sampling is essential

IronsourceandimplicationsSouthoftheAPF

JGOFS Hypothesis: FescarcitylimitsdSiutilizationsouthoftheSBACCImplications:

dFeinupwelledUCDWissufficientforcompletedSiconsumptiondFeismuchlowerinLCDWupwelledfurthersouthQuestion:Ifso,ishigherdFeinUCDWhydrothermal?

IronsourceandimplicationsNorthoftheAPF

Fe Recycling Hypothesis:

Landing:AerosolsourceofFeissufficientforPPintheNPacificAerosolFeisinsufficientforPPintheSPacific (P6TEIdata+Satellite-basedmodels)H1:LateralsourceofbioavailabledFeH2:PlanktonrecycleFemoreefficientlyintheSPacific(Rafter

hypothesis) InvokedbySchlosseretal.forSAtlantic Testableusingsiderophoremeasurements(ReneBoiteau/

DanRepeta) ParticlesintheSPSGwithultralowdustfluxesshouldhave

highFe/TiratiosifthereisasourceofdFefromupwellingorfromlateraltransportbycurrents.

Nfixation:ControlsandConsequencesGP15 + GP17 will sample:

3regimesw/oNfixation(SNP,EqPac,SoOcean)2regimeswithNfixation(NPSG,SPSG)

Wangetal.,Nature,2019(w/News&ViewsbyGruber) offerpredictions(hypotheses)aboutglobalNfixation testablewithGEOTRACESdataonGP15+GP17

DodissolvedandparticulateTEIdata(includingNisotopes) supporttheseparadigms? WhatroledoesFeplay?

ComparewithNAtlantic(GA03)totesthypothesisthat lowPlimitsNfixationintheNAtlantic (needsGEOTRACESnanonutrients)

SoOceanprocessessetend-memberwatermassmicronutrientcomposition

Biological uptake:

ForCd,Zn,others(?)ismuchgreaterintheSouthernOcean thanatlowerlatitudes.Why?

H1:ResponsetoFelimitationH2:dMeinupwelledwaterexceedsligandconcentration Highconcentrationsoffreeinorganicions “Luxury”uptakeoffreemetal

SoOceanprocessessetend-memberwatermassmicronutrientcomposition

Regeneration:

ForCd,Zn,others(?)ismuchgreaterintheSouthernOcean thanatlowerlatitudes(becauseofhighuptake).

Highlatitudedataneededtosetend-memberMe/Pratios

EssentialforOMPAanalysistoderiveregeneratedTEIs atlowerlatitudes

Notonlymicronutrients e.g.,OMPAevidenceforsubstantialbenthicREEsource

SoOceanprocessessetend-memberwatermassmicronutrientcomposition

Regeneration:

ForCd,Zn,others(?)ismuchFASTERintheSouthernOcean thanatlowerlatitudes(becauseofhighuptake).

But-Martinpowerlawabsolute“b”values(0.2–0.5)seemto

betoosmall(bothinSoOcandatlowlatitudes) BasedoninversemodelofRoshanetal.(2018)

TestableusingGEOTRACESdata Calculate“b”valuesforTEIsacrossgradientsin nutrients,productivityandecosystems

SamplingoffChile

PDWfluxtoSoOcean

concentratedalongeasternboundary

3Hedistributionandflowinthelayer27.98kgm−3<γn<28kgm−3

a)  Observationsb)  Posteriormean

Faure&Speer,2012SeealsoTamsittetal.2017,2018

PDWfluxtoSoOcean

concentratedalongeasternboundary

HighresolutionsamplingneededapproachingChilemargin.

Faure&Speer,2012SeealsoTamsittetal.2017,2018

GP17cruiseandproposaltimeline

Tentative timeline for discussion (working backwards) Cruise (s) Nov 2021 – Feb 2022 Fill-gap proposals Feb 2021 PI proposals Aug 2020 Management proposal Feb 2020 Iftwoshipsthenbacktobackorinsequentialyears?

MotivationfortheGP17Section1) Ultra-oligotrophic South Pacific Gyre

Low dust, productivity, particles – impact on scavenging? Record deep DCM – impact on colloid cycling?

2) Southern Ocean regulation of global biological pump efficiency Upwelling hot spots – source of Fe? Dust vs. upwelling sources of micronutrients SE Pacific low biomass – control by Fe, MLD, other?

3) Dispersal of continental sources of micronutrients Basal melt Subglacial meltwater runoff Extent of signal

4) Outflow of Fe carried by Pacific Deep Water Large Fe sources from margins and ridges How much reaches Southern Ocean? Stabilization of Fe (and other TEIs) by ligands

BIOSOPE–DeepChlorophyllMaximum

FromClaustreetal.,2008

Are colloidal TEIS removed from the DCM under extreme: 1) low dust input 2) Deep DCM?

SPGLocalhydrothermalsignalunlikely

FromFrankiePavia,LDEO

German UltraPac section – 2015/2016 Geostrophic transport is eastward

SPGLocalhydrothermalsignalunlikely

FromFrankiePavia,LDEO

Updated map δ3He at 2500 m

GP17

MotivationfortheGP17Section1) Ultra-oligotrophic South Pacific Gyre

Low dust, productivity, particles – impact on scavenging? Record deep DCM – impact on colloid cycling?

2) Southern Ocean regulation of global biological pump efficiency Upwelling hot spots – source of Fe? Dust vs. upwelling sources of micronutrients SE Pacific low biomass – control by Fe, MLD, other?

3) Dispersal of continental sources of micronutrients Basal melt Subglacial meltwater runoff Extent of signal

4) Outflow of Fe carried by Pacific Deep Water Large Fe sources from margins and ridges How much reaches Southern Ocean? Stabilization of Fe (and other TEIs) by ligands

SEPacificLowChlorophyll–Why?

https://earthobservatory.nasa.gov/IOTD/view.php?id=4097

SEPacificLowChlorophyllrepresentedindifferent

NPPmodels

Winter(left)andsummer(right)NPPFromArteagaetal.,JGR-O,2018

SEPacificLowChlorophyllrepresentedindifferent

NPPmodels

Winter(left)andsummer(right)NPPFromArteagaetal.,JGR-O,2018

Why?LowFesupply?Deepmixedlayers?

SEPacific–DeepWinterMixedLayers

ButMLDinsummerseemsnottobeexceptional.Snapshotfrommonthlyanimationat:https://www.pmel.noaa.gov/mimoc/mimoc_gallery.html

Eddy-drivenupwellinghot-spotsassociatedwithtopography

Locationswhereparticlesreleasedindeepwaterat30°Supwellacross200m.Upwellingisconcentratedin5regionsoftopographyGP17willsampleat2locationsdownstreamofPARhotspot–Fegradient?Tamsittetal.,2017

MotivationfortheGP17Section1) Ultra-oligotrophic South Pacific Gyre

Low dust, productivity, particles – impact on scavenging? Record deep DCM – impact on colloid cycling?

2) Southern Ocean regulation of global biological pump efficiency Upwelling hot spots – source of Fe? Dust vs. upwelling sources of micronutrients SE Pacific low biomass – control by Fe, MLD, other?

3) Dispersal of continental sources of micronutrients Basal melt Subglacial meltwater runoff Extent of signal

4) Outflow of Fe carried by Pacific Deep Water Large Fe sources from margins and ridges How much reaches Southern Ocean? Stabilization of Fe (and other TEIs) by ligands

40

Highbiomassinsomeareassuggestbenthicsourceofironstimulatingphytoplanktongrowth

SeaWiFSImagespreparedforCROZEXProgramCourtesyofRaymondPollardSOC

South-to-NorthsectionofdissolvedFenear90°W(inredonmap)fromdeBaaretal.(1999)

AmundsenseasummaryfromPeteSedwick

South North

DissolvedFedatafromPineIslandPolynya(Gerringaetal.,2012)andGPpr03cruisereport

North-to-SouthDFesectionalongboxinmap

North-to-SouthDFesectionalongboxinmap DFeprofilesfromStn3(seemap)andStn160(inACCnear66°30’S,128°W)

AmundsenseasummaryfromPeteSedwick

SouthNorth

DissolvedtracemetaldatafromAmundsenSeaPolynya(Sherrelletal.,2015)–Shelfsedimentandiceshelfmetalsources.

North-to-SouthDFesectionalongboxinmapDoesnotextendbeyondshelfbreak.

NS

AmundsenseasummaryfromPeteSedwick

AmundsenSeaOden-2007

AmundsenSea–Oden,2007HighTMconcentrations(exceptMn)extendbeyondtheshelfbreak-Sherrellunpublished

CLIVARSP4-2011

ChrisMeasures–unpublisheddata,figuresfromPosterat2012OSM

Circumpolar Section

150˚W Section 170˚W Section

Ross Sea

Antarctic Peninsula

150˚W Section

Coastal inputs from the Antarctic continent

67˚S 76˚S

CLIVARSP4–2011150°WSection

ChrisMeasures–unpublished,Posterat2012OSM

N S

CLIVARSP4–2011CircumpolarSection

ChrisMeasures–unpublished,Posterat2012OSM

Circumpolar Section

177˚E 73˚W

CoastalinputsofFeandMnfromAntarcticPeninsula

East–WestgradientsinmacronutrientsMayalsoinfluencediatomproductivity

Nowotarski,Morton,Neeley,Hatta,Landing,Measures,Grand-PosterComplementsofPeteMorton

HighNO3andlowSiintheeast;UniformlylowFeexceptnearmargins

MotivationfortheGP17Section1) Ultra-oligotrophic South Pacific Gyre

Low dust, productivity, particles – impact on scavenging? Record deep DCM – impact on colloid cycling?

2) Southern Ocean regulation of global biological pump efficiency Upwelling hot spots – source of Fe? Dust vs. upwelling sources of micronutrients SE Pacific low biomass – control by Fe, MLD, other?

3) Dispersal of continental sources of micronutrients Basal melt Subglacial meltwater runoff Extent of signal

• TM from coastal sources extend off the shelf. • How far, and to what extent do they contribute micronutrients

to the broader Southern Ocean? • Provenance and rate tracers are needed.

Challenges-UncertaintyaboutSeaIce

MotivationfortheGP17Section1) Ultra-oligotrophic South Pacific Gyre

Low dust, productivity, particles – impact on scavenging? Record deep DCM – impact on colloid cycling?

2) Southern Ocean regulation of global biological pump efficiency Upwelling hot spots – source of Fe? Dust vs. upwelling sources of micronutrients SE Pacific low biomass – control by Fe, MLD, other?

3) Dispersal of continental sources of micronutrients Basal melt Subglacial meltwater runoff Extent of signal

4) Outflow of Fe carried by Pacific Deep Water Large Fe sources from margins and ridges How much reaches Southern Ocean? Stabilization of Fe (and other TEIs) by ligands

Can’trelyonmodelsforFesupplyfromdeepwatertoSoOceaneuphoticzone

Upwellingtrajectorydependsonmodelresolution

Magenta=1°resolution;Yellow=0.1°ResolutionDrakeetal.,GRL,2018

Upwellingtransittimeto300-misobathdependsonmodelresolution

LagrangiantimescalesofCDWupwellingdecreasefrom87yearsto31yearsto17yearsastheoceanresolutionisrefinedfrom1°to0.25∘to0.1°.Drakeetal.,GRL,2018;SimilarresultsinTamsittetal.,.2017:“Thetimescaleforhalfofthedeepwatertoupwellfrom30°Stothemixedlayeris~60–90years.”

Upwellingtransittimeto300-misobathdependsonmodelresolution

LagrangiantimescalesofCDWupwellingdecreasefrom87yearsto31yearsto17yearsastheoceanresolutionisrefinedfrom1°to0.25∘to0.1°.ThetimescaleupwellingiscomparabletotheresidencetimeofdFeinthedeepocean.WithlargeuncertaintiesinbothtransittimesandresidencetimesoneneedsempiricalconstraintsonthesupplyofdFetotheSouthernOceaneuphoticzonebyupwelling.

GP17PlausibleLogistics–requiresPalmer