2019-20 Honours project - Investigating the source of the high nitrate, low oxygen layer in the Leeuwin Current

Data for the project -Investigating the source of the high nitrate, low oxygen layer in the Leeuwin Current- is including in the file. The data include CTD data, ADCP data and Triaxus data from RV Investigator (Voyage IN2019_V03). Also the Sea Surface Height satellite data and CSIRO Atlas of Regional Seas (CARS) data are included as the supporting data.

The MATLAB code including the code that calculate the rotated velocity and the transport of the EGC current in upper 300m including volume transport, salinity transport, heat transport and oxygen transport.

The nitrate data from Triaxus is uncompleted and will be upload later with the code for calculating the nitrate transport.

Identification info

Date (Creation): 2020-08-27

Principal investigator

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Han, Meng

IMAS - Hobart

Private Bag 129

Hobart

Tasmania

7001

Australia

Collaborator

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Phillips, Helen

IMAS - Hobart

Private Bag 129

Hobart

Tasmania

7001

Australia

ORCID ID >

Credit: IMAS Honours Student Program 2019-2020

Status: On going

Point of contact

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Phillips, Helen

IMAS - Hobart

Private Bag 129

Hobart

Tasmania

7001

Australia

ORCID ID >

Temporal resolution: P0Y1M0DT0H0M0S

Topic category

Oceans

Extent

Temporal extent

Time period: 2019-05-13

Vertical element

Minimum value: 10

Maximum value: 2000

Identifier: EPSG::5715

Name: MSL depth

Maintenance and update frequency: As needed

Keywords (Theme)

Leeuwin Current
Eastern Gyral Current
HNLDO layer

NASA/GCMD Keywords, Version 8.5

Australian and New Zealand Standard Research Classification (ANZSRC): Fields of Research

Chemical Oceanography
Physical Oceanography

Keywords (Theme)

time
WOCE date
WOCE time of day
pressure
latitude
longitude
distance
Water depth
Primary temperature
Temperature flag
Primary SBE43 Oxygen
Biospherical PAR
Chlorophyll
Decimal day
Longitude
Latitude
depth
Zonal velocity component
Meridional velocity component
analysis time
LONGITUDE
gridded (adjusted) sea level anomaly
gridded sea level
eastward geostrophic velocity
northward geostrophic velocity

AODN Discovery Parameter Vocabulary

Resource constraints

Classification: Unclassified

Resource constraints

Use limitation: The data described in this record are the intellectual property of the University of Tasmania through the Institute for Marine and Antarctic Studies.

Resource constraints

Linkage: http://i.creativecommons.org/l/by/4.0/88x31.png
License Graphic

Title: Creative Commons Attribution 4.0 International License

Website: http://creativecommons.org/licenses/by/4.0/
License Text

Other constraints: The citation in a list of references is: citation author name/s (year metadata published), metadata title. Citation author organisation/s. File identifier and Data accessed at (add http link).

Language: English

Character encoding: UTF8

Content Information

Content type: Physical measurement

Description: time for Triaxus data for leg1, leg2_1, leg2_2, leg3

Name: time

Name: time

Name: minutes since 1900-01-01 00:00:00

Description: date for Triaxus data

Name: WOCE date

Name: woce_date

Name: yyyymmdd UTC

Description: time of a day in Triaxus data

Name: WOCE time of day

Name: woce_time

Name: WOCE time of day

Description: pressure of Triaxus data

Name: pressure

Name: pressure

Name: decibar

Description: latitude of Triaxus data

Name: latitude

Name: latitude

Name: degree_north

Description: Longitude of Triaxus data

Name: longitude

Name: longitude

Name: degree_east

Description: distance of Triaxus data

Name: distance

Name: distance

Name: km

Description: Triaxus data

Name: Water depth

Name: waterDepth

Identifier: http://vocab.nerc.ac.uk/collection/P06/current/ULAA

Name: Metres

Description: Triaxus

Name: Primary temperature

Name: temperature

Identifier: http://vocab.nerc.ac.uk/collection/P06/current/UPAA

Name: Degrees Celsius

Description: Triaxus

Name: Temperature flag

Name: temperatureFlag

Name: NAN

Description: Triaxus

Identifier

Code: Practical salinity of the water body

Name: salinity

Identifier: http://vocab.aodn.org.au/def/unitsofmeasure/entity/481

Name: Practical Salinity Unit

Description: Triaxus

Name: Primary SBE43 Oxygen

Name: oxygen

Name: uM

Description: Triaxus

Name: Biospherical PAR

Name: par

Name: uE/m^2/sec

Description: Triaxus

Name: Chlorophyll

Identifier

Code: Concentration of chlorophyll per unit volume of the water body

Name: chlorophyll

Identifier: http://vocab.nerc.ac.uk/collection/P06/current/UGPL

Name: Micrograms per litre

Description: ADCP

Name: Decimal day

Name: time

Name: days since 2019-01-01 00:00:00

Description: ADCP

Name: Longitude

Name: lon

Name: degree_east

Description: ADCP

Name: Latitude

Name: lat

Name: degree_north

Description: ADCP

Name: depth

Name: depth

Identifier: http://vocab.nerc.ac.uk/collection/P06/current/ULAA

Name: Metres

Description: ADCP

Name: Zonal velocity component

Name: u

Name: Zonal velocity component

Description: ADCP

Name: Meridional velocity component

Name: v

Name: Meridional velocity component

Description: SSH

Name: analysis time

Name: TIME

Name: days since 1985-01-01 00:00:00+00:00

Description: SSH

Name: LONGITUDE

Name: longitude

Name: degrees_east

Description: SSH

Name: gridded (adjusted) sea level anomaly

Name: GSLA

Name: m

Description: SSH

Name: gridded sea level

Name: GSL

Name: m

Description: SSH

Name: eastward geostrophic velocity

Name: UCUR

Identifier: http://vocab.nerc.ac.uk/collection/P06/current/UVAA

Name: Metres per second

Description: SSH

Name: northward geostrophic velocity

Name: VCUR

Identifier: http://vocab.nerc.ac.uk/collection/P06/current/UVAA

Name: Metres per second

Distribution Information

Distribution format

NCfile, m file

OnLine resource: DATA ACCESS - RV Investigator (IN2019_V03) CTD, ADCP and Triaxus data [direct download]

OnLine resource: DATA ACCESS - Matlab codes [direct download]

OnLine resource: DATA ACCESS - all RV Investigator data, Matlab code and supporting data [explore all files]

OnLine resource: THESIS - Investigating the source of the high nitrate, low oxygen layer in the Leeuwin Current [PDF direct download]

Resource lineage

Statement: In this study, data was collected onboard the RV Investigator (Voyage IN2019_V03) between May 13 and June 14, 2019. This voyage explored the physical, biogeochemical and ecological processes in the Southeast Indian Ocean. Its objectives including quantifying physical, chemical and biological properties along the 110°E line and investigating the sources of nitrogen to the region. A Conductivity-Temperature-Depth (CTD) profiler was deployed wat each station along 110°E line. Stations were 1.5 degrees apart in longitude and profiled from the surface to the seafloor. A lowered Acoustic Doppler Current Profiler (LADCP) was also attached to the CTD rosette to measure current speed and direction at each depth. Triaxus data was collected along three transects through the EGC. Triaxus is an instrument that is towed behind a vessel to provide high resolution data of water properties. In this study it profiled from the surface to a depth of 300m. Data from the voyage can be download from CSIRO website.(https://www.cmar.csiro.au/data/trawler/survey_details.cfm?survey=IN2019_V03).(https://www.marlin.csiro.au/geonetwork/srv/eng/search#!3bbb16fc-ecbe-4ad7-9f5d- 74e5e052714c). CSIRO Atlas of Regional Seas (CARS) data can also download from website (http://www.marine.csiro.au/atlas/). The sea surface height data is accessed from the Australian Ocean Data Network (AODN). In this study, we use the sea surface height data that has been delayed mode processed. It contains gridded (adjusted) sea level anomaly (GSLA), gridded sea level (GSL) and surface geostrophic velocity (eastward and northward velocity components) for the Australasian region. (https://portal.aodn.org.au/search). Velocity data from the ADCP was transformed into a new coordinate system whose two axes are perpendicular to the Triaxus track (rotated x-axis) and along the Triaxus track (rotated y-axis) using the code comp2speed and speed2comp which need to calculate rotation of the velocity first. Rotation was calculated using the equation: 𝑟𝑜 = tan−1 (∆𝑙𝑜𝑛) ∗ 180/𝜋 Volume transport, temperature transport, salinity transport, oxygen transport as well as nitrate transport of EGC were calculated in each grid cell. The summed value in each grid cell is called the sum transport. The volume transport in each grid-cell within the EGC is given by the product of the area of the cell times the cross-track velocity. Each cell is then summed over cells where the EGC is present (across-track velocity > 0.02ms-1). This gives the total transport of the EGC in each of the three transects. Volume transport Q (t) is given by Equation(2): 𝑸(𝒕) = ∑ ∆𝒙 ∆𝒛 𝒗(𝒙, 𝒛, 𝒕) (2) Where, x is the width of the grid cells (500m); z is the height of the grid cells (1m) and v is cross-track velocity. The unit of Q(t) is m3/s which is equal to 1 x 10 -6 Sverdrups (Sv). To calculate heat transport, we use Equation (3): 𝑸𝒉𝒆𝒂𝒕(𝒕)=∑𝝆𝑪𝒑(𝑻−𝑻𝒓𝒆𝒇)∆𝒙∆𝒛𝒗 (3) Where,  is the density of sea water (which we treat as a constant of 1025 kg m-3). Cp is the specific heat capacity of seawater (the ratio of potential enthalpy to Conservative Temperature (J/ (kg K))). T is the conservative temperature and Tref is a reference temperature. In this study, the reference temperature is assumed to be 0 °C so that the heat transport is the total heat transport through the current. The unit of the heat transport is in Watts. The salt transport, relative to a specified reference salinity Sref, is given by: 𝑄𝑠𝑎𝑙𝑡(𝑡)=∑𝜌(𝑆−𝑆𝑟𝑒𝑓)∆𝑥 ∙∆𝑧∙ 𝑣 (4) In equation (4), S is the absolute salinity (g kg-1) and the reference salinity Sref is 0. Then the absolute salinity transport can be estimated using equation (4) in units of kg s-1. Oxygen and Nitrate transport are calculated using equation (5) and equation (6), respectively. 𝑄𝑜𝑥𝑦(𝑡) = ∑ 𝜌 ∙ 𝑂 ∙ ∆𝑥 ∙ ∆𝑧 ∙ 𝑣 (5) 𝑄𝑛𝑖𝑡(𝑡)=∑𝜌∙𝑁∙∆𝑥∙∆𝑧∙𝑣 (6) Where, O and N are the concentration of oxygen and nitrate (micromol/L), respectively. The unit for the oxygen transport and nitrate transport is mcromol/s.

Hierarchy level: Dataset

Metadata

Metadata identifier: 3b070ea7-6e83-42dd-a2f6-44bc5fb03718

Language: English

Character encoding: UTF8

Point of contact

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - IMAS Data Manager

Type of resource

Resource scope: Dataset

Metadata linkage: https://metadata.imas.utas.edu.au/geonetwork/srv/eng/catalog.search#/metadata/3b070ea7-6e83-42dd-a2f6-44bc5fb03718
Point of truth URL of this metadata record

Date info (Creation): 2021-04-21T19:26:50

Date info (Revision): 2021-04-21T19:26:50

Metadata standard

Title: ISO 19115-3:2018

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