Time Series Observations: Rationale/Motivation A Case ...solas-int.org/summerschool/lectures/2005lectures/Bates-BATS.pdf · Drawdown of pCO2 or DIC due to NCP NCP = Net community

Dr. Nicholas R. BatesSenior Research Scientist

Bermuda Biological Station For ResearchBermuda Biological Station For Research

Time Series Observations:A Case Study of the North Atlantic and

the BATS site

Rationale/Motivation

Gruber and Sarmiento, 2002Gruber and Sarmiento, 2002

Humans are changing atmospheric composition and climate

Thanks to Scott Thanks to Scott DoneyDoney


Takahashi et al., 2002Takahashi et al., 2002


Red Areas:Red Areas: Oceanic Source of COOceanic Source of CO22

Blue Areas:Blue Areas: Oceanic Sinks of COOceanic Sinks of CO22

Globally integrated flux: 2.2 PgC yr-1

Sabine et al., 2004Sabine et al., 2004


H. sapiens traitstop competitor for space (urbanization)

effective predator(overfishing)

prolific biogeochemical recycler (C, N, P, H20 cycles)

symbiotic relationships with other species (ranching, habitat protection)

Ecosystem responsehabitat loss

food web adjustment → ecosystem shift

ecosystem shiftatmospheric CO2 higher than past 105–106 yearshabitat gain/loss

Ecosystems in the AnthropoceneDomination of Ecosystems by H. sapiens

J.J. KleypasKleypasThanks: J. Kleypas, NCAR; Pearson and Palmer, 2000

Effects of Atmospheric CO2on Ocean Ecosystems

Increased CO2

Increased AtmosphericTemperature

Increased SST

IncreasedStability

Climatic Changes

Alteredstorm

frequency/intensity

Increaseddust (Fe

fertilization)

Increase in N2 fixation?

Increased Atmospheric CO2

Decrease in nutrients?

Increase in Photosynthesis

Changes in ecosystems?

Changes in ecosystems?

Thanks to Scott Thanks to Scott DoneyDoney/Joan /Joan KleypasKleypas

1. Time1. Time--series studies: Introduction to BATS.series studies: Introduction to BATS.2. Introduction to the BATS site in the North Atlantic.2. Introduction to the BATS site in the North Atlantic.3.3. Carbon imbalance, new production, new sources of Carbon imbalance, new production, new sources of

nitrogen, nitrogen fixation, connections to modes nitrogen, nitrogen fixation, connections to modes of climate variability (i.e., NAO).of climate variability (i.e., NAO).

4.4. TimeTime--scales of COscales of CO2 variability, interannual variability, interannual variability of COvariability of CO2 and oceanic sink of COand oceanic sink of CO2..

5. New technologies.5. New technologies.

Outline of Talk:

1.1. Introduction to timeIntroduction to time--series studies. series studies. 2. Introduction to the BATS site in the North Atlantic.2. Introduction to the BATS site in the North Atlantic.3.3. Carbon imbalance, new production, new sources of Carbon imbalance, new production, new sources of

nitrogen, nitrogen fixation, connections to modes nitrogen, nitrogen fixation, connections to modes of climate variability (i.e. NAO).of climate variability (i.e. NAO).

4.4. Timescales of COTimescales of CO2 variability, interannual variability variability, interannual variability of COof CO2 and oceanic sink of COand oceanic sink of CO2..


Outline:Global-scale processes may change climate andecological systems in unforeseen ways that could affectour political and economic stability. It is thereforeimperative that we learn as much as possible about the causes and effects of such change. The magnitude of the natural fluctuations is similar to or larger than thatpredicted to result, initially, from human-induced perturbations to global climate, making it difficult to clearly identify the sources of ecosystem variability.

Outline:

Chlorophyll biomass (SeaWifs)

Difference approaches for studyingcarbon and nitrogen in the ocean

Thanks to NASA/LODYCThanks to NASA/LODYC

From spaceFrom spaceDrifting instrumentsDrifting instruments

Observing ocean processes

Ship ExpeditionsShip Expeditions••Ocean timeOcean time--seriesseries••Ocean surveys and process studiesOcean surveys and process studies

Observing ocean processesDifferent approaches for studyingcarbon and nitrogen in the ocean

Thanks to BBSR/UCSB/BNLThanks to BBSR/UCSB/BNL

In the lab back homeMooring and buoys

An important contribution of present time-series programshas been to document the temporal evolution of CO2 in surface seawater and changing air-sea fluxes. Theseobservations have clearly shown the effect of differentmodes of climate variability (e.g. ENSO, PDO) on CO2fluxes and water column biogeochemistry.

Objectives of time-series studies:Time series measurements have also shown that theuptake of anthropogenic CO2 is variable over a widerange of time and space scales necessitatinga sustained observing program to monitor the changes inocean chemistry and CO2 uptake efficiency in the future.

Objectives of time-series studies:

The present time series programs have also helpedelucidate phytoplankton primary production in relation to climateperturbations. Phytoplankton occupy a central role in oceanicecosystems, as their nutrient uptake, growth, and sinkingmediate the biogeochemical fluxes of carbon and otherelements between the atmosphere, surface ocean, and deepocean. They also influence the penetration depth of solarenergy and thus influence the ocean heat budget.

Objectives of time-series studies:Because the atmosphere and oceans are physically coupled,climate exerts strong effects on the marine biogeochemistryand food web mediated by phytoplankton.

Objectives of time-series studies:

time

space1 m2 1 km2 GlobeOcean

BasinRegional(106 km2)

centuries

decadal

Inter-annual

seasonal

daily

Remote sensing

hourly

Process Studies

Repeat Trans-basin

Sections

VOS

surface pCO2

Shipboard

Time-Series

Moored

Time-Series

Different Time and Space Scales

• Time series data, augmented with information from satellites and gliders, will span many scales of variability.

time

space1 m2 1 km2 GlobeOcean

BasinRegional(106 km2)

centuries

decadal

Inter-annual

seasonal

daily

Remote sensing

hourly

Process Studies

Repeat Trans-basin

Sections

VOS

surface pCO2

Shipboard

Time-Series

Moored

Time-Series


• The major focus in the early years is seasonal and spatial pattern of the physics, nutrient chemistry, and primary production.

time

space1 m2 1 km2 GlobeOceanBasin

Regional(106 km2)

centuries

decadal

Inter-annual

seasonal

daily

Remote sensing

hourly

Process Studies

Repeat Trans-basin

Sections

VOS

surface pCO2

Shipboard

Time-Series

Moored

Time-Series


• As the time series mature, the data will facilitate rigorous study of processes at longer time scales, such as the PDO and NAO.

• Global atmospheric flask network with biweekly for CO2 and other species (e.g., methane, N2O, halocarbons, etc.) • CO2 interhemispheric gradient places strong constraints on source/sink patterns.

Atmospheric Time-series

P. TansP. Tans

Open-ocean Time-series

Characterize the natural variability and secular trends in the ocean carbon cycle and determine the physical and biological mechanisms controlling the system

existing/planned mooringsphase-2 & new moorings(U.S. and international)

Ocean Time-series

S.S. DoneyDoney

Ocean Time-series

Ocean Time-series

Diverse topics asmid-water energy flow and benthic food webs, microbial recycling of nutrients, the formation ofthin biological layers, natural iron fertilization of the ocean.

An important goal of time-series efforts is to provide basic physical, chemical, and biological context for a number of other studies.

1. Introduction to time1. Introduction to time--series studies.series studies.2. Introduction to the BATS site in the North Atlantic.2. Introduction to the BATS site in the North Atlantic.3.3. Carbon imbalance, new production, new sources of Carbon imbalance, new production, new sources of

nitrogen, nitrogen fixation, connections to modes nitrogen, nitrogen fixation, connections to modes of climate variability (i.e. NAO).of climate variability (i.e. NAO).



Outline:

BATSBATSALOHAALOHA

Ocean Time-series (since 1988)

Karl et al., 2001Karl et al., 2001

BATSBATS

Sargasso Sea

Gulf Stream

• Monthly sampling16 core cruises a year 2-3 validation cruises

0-4200 m• 24 Hydrostation S

cruises per year.

Bermuda Atlantic Time-series Study

Hydrostation S (1954Hydrostation S (1954--present)present)

Bermuda Bermuda Testbed Testbed Mooring Mooring (BTM) (1994(BTM) (1994--present)present)

BATS (1988BATS (1988--present)present)

Hydrostation S

BATS/OFP SITE

BATS Deployment Area

(32° 10N, 64° 30W)

(31° 50N, 64° 10W)

32°32°

64°

64°65°

65°

AEROCE Tower

Harbour Radio Tower200 m2000 m4000 m

Ocean Flux Program (OFP) Ocean Flux Program (OFP) (1978(1978--present)present)

AEROCE Tower AEROCE Tower (atmosphere sampling)(atmosphere sampling)

Time-series Studies near Bermuda Ocean Flux Program (OFP)

The OFP sediment trap time-series mooring is located in the western Sargasso Sea at 31 50'N, 64 10'W, approximately 75 km southeast of Bermuda. The traps have continually sampled deep ocean fluxes with a resolution of either two months (1978-1989) or two weeks (1989 to present). There is a 21+ year flux record at 3200 m (>85% temporal coverage), a 13+ year record at 1500 m, and a 10+ year record at 500 m.

M. Conte, WHOIM. Conte, WHOI

The regular seasonal pattern in SST at Hydrostation S is shown below. The black line ( -) is the average of all temperature data (x) available in the time series from 1955 through 1997 for each month. The two dotted red lines (- -) show the maximum and minimum temperatures observed over this time for each month. Error bars are based on standard deviation values. R. Johnson, BBSRR. Johnson, BBSR

Seasonality of SST (Hydrostation S) Observations at BATS

Temperature

Salinity

Time-series of Temperature & Salinity Time-series of Nitrate & PhosphateNitrate and Phosphate Variability

TCO2 and Primary Production VariabilityPrimary Productivity and TCO2 Annual Primary Productivity and Export

14C primary productivity

Particulate Organic Matter

BATS

• Net primary production (NPP) describes the net fixation of inorganic carbon by autotrophic organisms, i.e., the difference between gross primary production (GPP) and autotrophic respiration.• The difference between NPP and heterotrophic respiration is named net community production (NCP) [Williams, 1993].

Annual Primary Productivity and ExportBATS

1.1. TimeTime--series studies: Introduction to BATS.series studies: Introduction to BATS.2. Introduction to the BATS site in the North Atlantic.2. Introduction to the BATS site in the North Atlantic.3.3. Carbon imbalance, new production, new sources of Carbon imbalance, new production, new sources of

nitrogen, nitrogen fixation, connections to modes nitrogen, nitrogen fixation, connections to modes of climate variability (i.e., NAO).of climate variability (i.e., NAO).



Outline:

COCO22

OrganicOrganicMatterMatter


Upwelling/Upwelling/CirculationCirculation

PhotosynthesisPhotosynthesis

RespirationRespiration

Gas ExchangeGas Exchange

AtmosphereAtmosphere

OceanOcean

Aphotic Aphotic ZoneZone

RemineralizationRemineralization

Sinking of Sinking of ParticlesParticles

Ocean carbon cycle processes

COCO22

COCO22



Upwelling/Upwelling/CirculationCirculation

PhotosynthesisPhotosynthesis

AtmosphereAtmosphere

OceanOcean

Aphotic Aphotic ZoneZone

RemineralizationRemineralization

Sinking of Sinking of ParticlesParticles

Ocean nitrogen cycle

NONO33

NONO33

New production paradigm without NNew production paradigm without N22 fixationfixation

Drawdown of Seawater pCO2 and nitrate North Atlantic Ocean near the NABE siteNorth Atlantic Ocean near the NABE site

Drawdown of Drawdown of ppCOCO22 or DIC due to NCPor DIC due to NCPNCP = Net community productivityNCP = Net community productivity

North PacificNorth Pacific

NCP

NCP

Mixing

Takahashi Takahashi et alet al., 2002., 2002

NCP and drawdown of seawater pCO22

New production = export productionNew production = export production

Ross SeaRoss Sea

2300

2250

2200

2150

2100

10 15 20 25 30 35

DIC

(D

IC ( µµ

mol

es/k

g)m

oles

/kg)

Nitrate + nitrite (Nitrate + nitrite (µµmoles/kg)moles/kg)

Blue: Blue: NovNov--Dec. 1994Dec. 1994

Green:Green:Dec. 1995Dec. 1995--Jan. Jan.

19961996

C:N = 6.7:1C:N = 6.7:1

DIC & nitrate drawdown in the Ross Sea

Bates Bates et alet al., 1998a., 1998a

High Rates of Productivity on ShelvesChukchi and Beaufort Sea Chukchi and Beaufort Sea shelfshelf--slope NCPslope NCPThe highest rates of net community productivity, NCP (~1000-2850 mg C m2

d-1), calculated from DIC and nitrate changes, occurred on the shelf in the Barrow Canyon region of the Chukchi Sea and east of Point Barrow in the western Beaufort Sea.

Bates et al., 2005a,bBates et al., 2005a,b

SpringSpring

SummerSummer

Takahashi Takahashi et alet al., 2002., 2002

Global drawdown of pCO22

BATSBATS Gulf Stream

• Monthly sampling16 core cruises a year 2-3 validation cruises

0-4200 m• 24 Hydrostation S

cruises per year.

Seasonal Changes of DIC at BATS

2070

2060

2050

2040

2030

2020

2010

2000

1990

J F M A M J J A S O N D

440

420

400

380

360

340

320

300

pp COCO

22(( µµ

atm

)at

m)

Tem

pera

ture

cor

rect

edTe

mpe

ratu

re c

orre

cted

DIC

(D

IC ( µµ m

oles/kg)m

oles/kg)

DICDIC

ppCOCO22C:N = ?C:N = ?

Michaels Michaels et alet al., 1994; Bates ., 1994; Bates et alet al., 1996., 1996

Spring-summer drawdown of TCO2

NCP occurs in the absence NCP occurs in the absence of of measureable measureable nutrientsnutrients

New production (NCP) > export productionNew production (NCP) > export production

Increase in Increase in 1313C during springC during spring--summer periodsummer period

Gruber et al., 2002Gruber et al., 2002

Spring-summer drawdown of TCO2

Cause: productivity as evidenced from Cause: productivity as evidenced from δδ1313C dataC data

Carbon and N imbalanceCarbon and N imbalance

Michaels et al., 1994; Bates et al., 1996Michaels et al., 1994; Bates et al., 1996

Biology at work! But how?Biology at work! But how?

Jan Feb Mar Apr May Jun July Aug Sep Oct Nov DecSeasonal modification bySeasonal modification by biologybiology andand gas exchangegas exchange

makes the Sargasso Sea a makes the Sargasso Sea a sinksink for atmospheric COfor atmospheric CO22..

pp COCO

22(( µµ

atm

)at

m)

460460440420400380360340320300

BiologyBiology (net community production) and (net community production) and airair--sea COsea CO22gas exchangegas exchange reduce reduce ppCOCO22 to the to the black line.line.

Impact on CO2 Fluxes

J F M A M J J A S O N D

Mixed layer

Seasonal Cycle of C and N at BATS

DOC contributes to export production as well as POCDOC contributes to export production as well as POC

Circulation: Schmitz and McCartney, 1993Circulation: Schmitz and McCartney, 1993

N S

38°N 22°N

N2 (N*)

Gulf Stream

NO3

N2

•Winter mixing?•Mesoscale eddies?

•Local N2 fixation or transport?•Transport of DON and NO3?

•Non-redfield C:N:P processes?

DON and/or NO3

Where does the new N come from?

NO3

Mixed layer

Seasonal Cycle of C and N at BATS

DOC contributes to export production as well as POCDOC contributes to export production as well as POCSee Carlson See Carlson et alet al., 1994., 1994

Mixed layer

NO3

N2

DON?

What are the sources of new N?

NO3

Many unanswered questions?Many unanswered questions?

Winter mixing and new production

Primary productivity ~150 g C m-2 year-1

New production ~ 0.6 mol N m-2 year-1

Mixed layer depth

Nitrate injection

Export

Lomas Lomas et alet al., 2005., 2005

Biomass build up

Winter new production

Export

J u l i a n D a y

6 6 6 7 6 8 6 9 7 0 7 1 7 2 7 3 7 4

nDIC

(um

ol/k

g)

2 0 5 8

2 0 6 0

2 0 6 2

2 0 6 4

2 0 6 6

2 0 6 8

2 0 7 0

J u l i a n D a y

6 6 6 8 7 0 7 2

Int.

PP

(mgC

m-2

d-1

)

0

5 0 0

1 0 0 0

1 5 0 0

2 0 0 0


Winter new production


•Alternation between deep and shallow mixed layer depths does lead to nutrient injections into the deeper parts of the mixed layer, 80 – 140 m.

–Mixed layer deepened then shoaled over the next few days–Biomass increased only slightly–Primary production went up dramatically–Export production went up dramatically

Mixed layer Carbon(mg C m-2 d-1)

Feb 2004 Front BATS Winter MixingTPM flux 288 + 69 198 + 98POC flux 49 + 11 37 + 20BSiO flux 14 + 3 6 + 4

Primary Production 1,595 + 178 474 + 58

DIC drawdown) 1,620 – 1,920 0

Period of ‘normal’ PrimaryProductivity (JD 48-52)

Period of higher PrimaryProductivity (JD 66-70)

Diatom response?

Summer production: role of eddies

NO3

Export

Increased chlorophyll biomassin mesoscale eddies

Summer production: EDDIES project

Determining the biogeochemical and biological responses to mesoscale eddiesin the North Atlantic subtropical gyre EDDIES Project P.I.EDDIES Project P.I.’’ss

D. D. McGillicuddyMcGillicuddy, W.J. Jenkins, W.J. JenkinsJ. J. LedwellLedwell, K.O. Buesseler (WHOI) , K.O. Buesseler (WHOI) N.R. Bates (BBSR)N.R. Bates (BBSR)P. Falkowski (Rutgers) P. Falkowski (Rutgers) D. Siegel (UCSB) D. Hansell (RSMAS)D. Siegel (UCSB) D. Hansell (RSMAS)

Summer 2004

Mixed layer

NO3

N2

DON?

What are the Sources of New N?

NO3

Many unanswered questions?Many unanswered questions?

Summer production: role of N2 fixation

N2

N2 NO3

NASA photo of Trichodesmium patches

Colonies of diazotroph Trichodesmium

Increased new production due to nitrogen fixation?

NASA photo of Trichodesmium patches

Excess N (N*) and Oceanic N2 Fixation

Capone et al., 2005Capone et al., 2005

High N* in the thermocline of the North Atlantic subtropical gyre

Excess nitrate relative to the phosphate concentration expected from thermocline N:P ratios (i.e., N:P of 16:1)

Subtropical mode waterMost important volumetric component

High early geochemical estimatesSummer production: role of N2 fixation

N* = (N-16P+2.90)*0.87

Gruber and Sarmiento, 1997Gruber and Sarmiento, 1997

Excess N (or N*) relative to P

High N* in the thermocline of the North Atlantic subtropical gyre

Excess nitrate relative to the phosphate concentration expected from thermocline N:P ratios (i.e., N:P of 16:1)

Subtropical mode waterMost important volumetric component

Capone et al., 2005Capone et al., 2005

Definition of Excess Nitrate (�DINxs)

DINxs = N - 16P

where N is the concentration (µmoles kg-1) of nitrate (plus nitrite where available) and P is the concentration of soluble reactive phosphate (µmoles kg-1).

N* = (N - 16P + 2.90) x 0.87

where the constant (2.90) and multiplier are used to force the global mean N* to zero (Gruber and Sarmiento, 1997; Deutsch et al., 2001; Gruber and Sarmiento, 2001).

Hansell et al., 2004Hansell et al., 2004

1980 1990 2000

20

x

x

Nor

th A

tlant

icN

2Fi

xatio

n(T

g o r

1012

g N

yr-1

)

Biological Estimatesx Geochemical Estimates

xHansell et alCapone and Carpenter *Capone et al

Michaels et al

Gruber and Sarmiento

10

30

0

Nitrogen Fixation Rates (Tg N yr-1)

Hansell et al., 2004Hansell et al., 2004

Variability of DINxs (1988-2002)

Bates and Hansell 2005Bates and Hansell 2005

N.R. Bates, A.C Pequignet, and R.J. JohnsonBermuda Biological Station For ResearchBermuda Biological Station For Research

Source: Talley, 2000Source: Talley, 2000

North Atlantic Subtropical North Atlantic Subtropical Mode Water (STMW)Mode Water (STMW)

Interannual variability of the production of excess nitrate (DINxs) in the subtropical gyre remains poorly quantified.

Excess Nitrate in Mode Water

18°C 25°C4°C

STMW in the North Atlantic OceanGeneric winter Generic winter

location of STMW location of STMW formationformation

Geostrophic Geostrophic recirculation recirculation pathways of STMWpathways of STMW

Interannual variability of STMW formation is primarily associated with climate variability (i.e. North Atlantic Oscillation, NAO)

Images: Thanks to Norm Nelson, UCSB and John Marshall (MIT)Images: Thanks to Norm Nelson, UCSB and John Marshall (MIT)

Gulf Gulf StreamStream

Increasing Heat LossIncreasing Heat Loss

18°C 25°C4°C

STMW in the North Atlantic Ocean

Interannual variability of STMW formation is primarily associated with climate variability (i.e. North Atlantic Oscillation, NAO)

Images: Thanks to Norm Nelson, UCSB and John Marshall (MIT)Images: Thanks to Norm Nelson, UCSB and John Marshall (MIT) Transect Data: R/V Oceanus, June 2000Transect Data: R/V Oceanus, June 2000

Generic winter Generic winter location of STMW location of STMW

formationformation

Geostrophic Geostrophic recirculation recirculation pathways of STMWpathways of STMW

1818°°C C IsothemIsothem

17.817.8°°C C IsothemIsothem

18.218.2°°C C IsothemIsothem

STMW in the North Atlantic Ocean

Long-term excess nitrate variability

• low DINxs of ~0.5-0µmoles kg-1 in 1995-6 and 2001.

• high DINxs of ~2-5-3.0µmoles kg-1 in 1990 and 1999.

26.4-26.6 σΘ layer

26.8-27.0 σΘ layer

27.0-27.2 σΘ layer

H HL L

Bates and Hansell, 2004Bates and Hansell, 2004

DINxs Variability Across the Gyre

Mar 1995 R/V WB IIJuly 1995 R/V WB IIOct. 1995 R/V WB IISept 1997 A22June 2001 R/V OceanusJune 2001 R/V Oceanus

55°W64-66°W

A22(1997)

A20(1997)

Oceanus(2001)

• Not much data on the spatial distribution of DINxsBates and Hansell, 2004Bates and Hansell, 2004

Excess nitrate inventory:12.8 to 59.2 Tg N

Inventory of excess nitrate (ΣDINxs) estimated from the volume of STMW (VSTMW),

and DINxs value.

Inventory of DINxs


In Scenario 1, the production rate of excess nitrate was computed as the slope of a linear regression between DINxs and water mass age (from pCFC-12 age data) of

STMW from the WOCE A22 section

Production rate of DINxs (Tg N yr-1)

Scenario 1Prodn rate of 0.09 µmoles kg-1

yr-1; VSTMW = 1.66 x 1015 m3.2.1 Tg N yr-1


Production rate of DINxs (Tg N yr-1)

In Scenario 2, production rate of excess nitrate was computed from DINxs inventory (ΣDINxs) and residence

times (τSTMW of 10 years) for the STMW layer.

DINxs

Scenario 2 τ = 10 yearsVSTMW = 1.66 x 1015 m3.

DINxs values 1.0 µmoles kg-1 0.6 Tg N yr-1

2.8 µmoles kg-1 2.8 Tg N yr-1


Michaels et al. (1996), Gruber and Sarmiento (1997) estimates determined from thermocline values for N*; whereas Hansell et al. (2002) and this study determine

the rate of DINxs production per year.

Production rates of DINxs (Tg N yr-1)

Note: In order to compare rates directly with Michaels et al. (1996) and Gruber and Sarmiento (1997), rates of excess nitrate production are divided by a factor of 0.76 (equation 14; Gruber and Sarmiento, 1997).


1980 1990 2000

20

Nor

th A

tlant

icN

2Fi

xatio

n(T

g o r

1012

g N

yr-1

)

Geochemical Estimates

Hansell et al. 2004

Michaels et al 1996

Gruber & Sarmiento, 1997

10

30

0

Production rates of DINxs (Tg N yr-1)

Bates & Hansell, 2004


Climate connections: excess nitrate and dust deposition?

NA

ON

AO

NA

O

• higher DINxs and dust inputs to Sargasso Seaduring NAO +ve phase.

• lower DINxs and dust inputs to Sargasso Seaduring NAO-ve phase.


The NAO, a component of the The NAO, a component of the Arctic Oscillation (AO), is the sea Arctic Oscillation (AO), is the sea level pressure (SLP) difference level pressure (SLP) difference between between Ponta DelgadaPonta Delgada, Azores , Azores and and StykkisholmurStykkisholmur, Iceland , Iceland ((Hurrell Hurrell 1995).1995).

North Atlantic Oscillation (NAO)

Image: D. StephensonImage: D. Stephenson Data Image: T. OsbornData Image: T. Osborn

NAO NAO --ve ve state:state:

•• fewerfewer winterwinterstormsstorms

•• lessless rain rain in N. Europein N. Europe

•• coolercooler in in N. EuropeN. Europe


•• coolercoolerin subtropical gyrein subtropical gyre

Data Image: T. OsbornData Image: T. Osborn

NAO + NAO + ve ve state:state:

•• moremore rain rain in N. Europein N. Europe

•• warmerwarmer in in N. EuropeN. Europe

•• moremore winterwinterstormsstorms


•• warmerwarmerin subtropical gyrein subtropical gyre

Dust, N2 fixation, DINxs and NAO?r2 = 0.53

r2 = 0.42

r2 = 0.49

NAO +ve Phase NAO -ve Phase

Low Fe (<0.3 µm)

High Fe (>0.5 µm)

Long-term Changes

Bates 2005Bates 2005

•• Mixed layer TCO2 (µmoles kg-1 yr-1)TCO2 +1.20 + 0.35 (r2= 0.36*)nTCO2 +1.19 + 0.25 (r2= 0.37*)DO -0.10 + 0.24 (r2= 0.00)

STMW TCOSTMW TCO22

Surface TCOSurface TCO22

•• STMW TCO2 (µmoles kg-1 yr-1)TCO2/nTCO2 +2.22 + 0.27 (r2= 0.65) DO -0.58 + 0.22 (r2= 0.27)

Interannual Variability of CO2Uptake of anthropogenic CO2

Bates Bates et alet al., 2002., 2002

• Higher winter wind speeds in 1990’s compared to 1980’sGEOSECS data GEOSECS data TTO dataTTO dataKeeling dataKeeling dataBrewer data Brewer data BATS dataBATS data

* ** **

Variability of Carbon Storage?

* ** * *

* Extensive STMW formation Bates Bates et alet al., 2002., 2002

• Higher winter wind speeds in 1990’s compared to 1980’s

• Higher winter wind speeds in 1990’s compared to 1980’s

Mean winter wind speedMean winter wind speed

Mean annual wind speedMean annual wind speed

GEOSECS data GEOSECS data TTO dataTTO dataKeeling dataKeeling dataBrewer data Brewer data BATS dataBATS data

CO2 gas flux at the site of STMW formation should increase STMW by 2-3 µmoles kg-1 yr-1.

Increased Gas Exchange?


Post 1987: CO2 transferred to ocean interior

1960’s, 1970’s, early 1980’s: CO2 in STMW redistributed

Long-term CO2 sink >10 yearsShort-term CO2 sink ~1-4 years

NAO-ve State NAO+ve State


• Annual global ocean uptake of CO2 is about 2 Pg C yr-1. • Over the last 12 years, the extra uptake of CO2 into STMW (~ 0.6 to 2.8 Pg C) has the same range as the global annual uptake of CO2. • Since 1988, STMW has taken up (~ 0.05 to 0.23 Pg C yr-1). This is ~3 to 11% of the best estimate of annual uptake of CO2 into the global ocean.

2020°°NN 4040°°NN

3-11% of global CO2 uptake

Conclusions and Implications: A changed oceanic CO2 Sink in 1990’s

• New sources of nitrogen remain unquantified. Implications for the CO2 sink status of the North Atlantic Ocean.

• Excess nitrate within the STMW of the subtropical gyre was highly variable over the 1988-2001 period, with two extended periods of high DINxs values (~2.0-3.0 µmoles kg-1) in 1989-1990, and in 2000.

• Extended periods of low DINxs values (~0-0.5 µmoles kg-1) were observed in 1995, and 2001, with brief low DINxsperiods in 1992 and 1993.

• Production rates of excess nitrate for most of the 1988-2001 period were low (~0.6-2.8 Tg N yr-1).

• Excess nitrate values (~1.5-2.8 µmoles kg-1) and rates of excess nitrate production (~2.8 Tg N yr-1) were generally high during positive phases of the North Atlantic Oscillation (NAO) (e.g., 1989-1994; 1997-2000), and periods of higher atmospheric mineral dust input to the ocean.

Conclusions


Acknowledgements:

Thanks to:

A.H. Knap, M. Lomas, R.J. Johnson (BBSR)D.A. Hansell (RSMAS)A.F. Michaels (USC)

N. Gruber (UCLA)

Time Series Observations: Rationale/Motivation A Case ...solas-int.org/summerschool/lectures/2005lectures/Bates-BATS.pdf · Drawdown of pCO2 or DIC due to NCP NCP = Net community

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