1 Descriptive Section

1.1 Indicator category

Habitat-Physical

1.2 Indicator name

Oceanic Niño Index

Includes variable(s): ALL

1.3 Indicator brief description

The Oceanic Niño Index (ONI) measures differences over time in sea surface temperature relative to a baseline period in the Nino 3.4 region (5oN-5oS, 120o-170oW) of the tropical Pacific. Until February 2026, this index was used by NOAA to distinguish El Niño from La Niña conditions; it has now been replaced by the Relative Oceanic Niño Index.

1.4 Indicator visualization

The ONI oscillates between negative (warmer ocean water El Niño conditions) and positive (cooler ocean water La Niña conditions) phases every 2-7 years, and was in a positive phase as of late 2025.

2 SMART Attribute Section

2.1 Indicator documentation

2.1.1 Are indicators available for others to use (data downloadable)?

Yes

2.1.1.1 Where can indicators be found?

All marea indicators are here: https://github.com/MarEcosystemApproaches/marea

2.1.1.2 How often are they updated? Are future updates likely?

Unknown

2.1.1.3 Who is the contact?

Jamie C. Tam

2.1.2 Gather indicator statistics

2.1.2.1 Units

Indicator

Units

Oceanic Niño Index

deg C anomaly

2.1.2.2 Length of time series, start and end date, periodicity

General overview: Annual and Monthly

Indicator specifics:

Indicator

EPU

StartYear

EndYear

Oceanic Niño Index

Niño 3.4 Region (Pacific)

1950

2025

2.1.2.3 Spatial location, scale and extent

General overview: 5°N–5°S, 120°W–170°W

Indicator specifics:

Indicator

EPU

Oceanic Niño Index

Niño 3.4 Region (Pacific)

2.1.2.4 Management scale: all species, FMP level, species level, can it be aggregated or separated to different scales?

Basinwide scale applying to the entire Pacific with potential teleconnections to the Atlantic; cannot be aggregated or separated.

2.1.2.5 Uncertainty metrics

Uncertainty is captured in these variables:

character(0)

2.1.3 Are methods clearly documented to obtain source data and calculate indicators?

No methods documentation is provided

2.1.3.1 Can the indicator be calculated from current documentation?

No. No methods documentation is provided

2.1.3.2 Is code publicly available? up to date?

No. No link to code in metadata

2.1.3.3 Have methods changed over time?

Yes. This index will continue to be reported, but NOAA’s climate prediction center is going to use a Relative Oceanic Nino Index from February 2026 on (See https://www.weather.gov/media/notification/pdf_2026/pns26-05_Relative_ONI.pdf). The indicator data used in the marea package are here: https://www.cpc.ncep.noaa.gov/data/indices/oni.ascii.txt and the link to the new relative index is here https://www.cpc.ncep.noaa.gov/data/indices/RONI.ascii.txt The link for the source information has changed from what is reported below in the marea metadata: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml

2.1.4 Are indicator underlying source data linked or easy to find?

Yes. Source information included: NOAA CPC, https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml

2.1.4.1 Where are source data stored?

Source data stored at NOAA CPC, https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml

2.1.4.2 How/by whom are source data updated? Are future updates likely?

No. No source data steward information

2.1.4.3 How often are they updated?

Monthly at this specific link: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php

2.2 Indicator analysis/testing or history of use

2.2.1 What decision or advice processes are the indicators currently used in?

None known in the Mid-Atlantic.

2.2.2 What implications of the indicators are currently listed?

This is one indicator of the El Niño/Southern Oscillation (ENSO) pattern that affects atmospheric patterns and weather conditions globally. To declare El Niño or La Niña conditions, the SIO and ENSO sea surface temperature indicators need to be synchronized. See https://www.climate.gov/news-features/understanding-climate/climate-variability-southern-oscillation-index. Different regions can experience unusual flooding or droughts as a result of the ENSO conditions and their effects on winds, upwelling, water temperature, and changes in atmospheric pressure affecting precipitation. While drought or flooding could occur anytime, regional events may be more predictable during one phase or the other of SIO and ENSO. See https://www.ncei.noaa.gov/access/monitoring/enso/ and https://iri.columbia.edu/our-expertise/climate/enso/why-do-we-care-about-el-nino-and-la-nina/

2.2.3 Do target, limit, or threshold values already exist for the indicator?

Yes, criteria for this indicator (in combination with ENSO sea level air pressure indicators) are established to establish the current phase of ENSO conditions.

2.2.4 Have the indicators been tested to ensure they respond proportionally to a change in the underlying process?

Yes, this and other ENSO indicators were compared against the SOI for predicting El Niño, La Niña, or neutral conditions and this one performed well for detecting El Niño. See https://journals.ametsoc.org/view/journals/clim/16/8/1520-0442_2003_16_1249_aqeoei_2.0.co_2.xml Further testing suggested the use of the new relative version of this indicator (RONI). See https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso/roni/announcement.php

2.2.5 Are the indicators sensitive to a small change in the process, or what is the threshold of change that is detectable?

Yes, but this indicator was found to be insufficiently sensitive due to its calculation based on a baseline time period. The new RONI indicator is measured as temperature within the ENSO region relative to tropical waters outside the ENSO region and is considered more sensitive.

2.2.6 Is there a time lag between the process change and the indicator change? How long?

Unknown, may depend on how data are aggregated into the index

3 SMART rating

Category

Indicator

Element

Attribute

Rating

ElementRating

OverallRating

Habitat-Physical

Oceanic Niño Index

Specific

Described

1.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Specific

Units

1.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Specific

Spatial

1.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Specific

Uncertainty

0.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Specific

Methods

0.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Specific

Code

0.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Measurable

Available

1.0

0.8333333

0.7

Habitat-Physical

Oceanic Niño Index

Measurable

Online

1.0

0.8333333

0.7

Habitat-Physical

Oceanic Niño Index

Measurable

Contact

1.0

0.8333333

0.7

Habitat-Physical

Oceanic Niño Index

Measurable

SourceDat

1.0

0.8333333

0.7

Habitat-Physical

Oceanic Niño Index

Measurable

SourceAvail

1.0

0.8333333

0.7

Habitat-Physical

Oceanic Niño Index

Measurable

SourceContact

0.0

0.8333333

0.7

Habitat-Physical

Oceanic Niño Index

Achievable

Tested

1.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Achievable

Sensitivity

0.5

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Achievable

TimeLag

0.0

0.5000000

0.7

Habitat-Physical

Oceanic Niño Index

Relevant

Advice

0.0

0.6666667

0.7

Habitat-Physical

Oceanic Niño Index

Relevant

Implications

1.0

0.6666667

0.7

Habitat-Physical

Oceanic Niño Index

Relevant

TargThresh

1.0

0.6666667

0.7

Habitat-Physical

Oceanic Niño Index

Timebound

Frequency

1.0

1.0000000

0.7

Habitat-Physical

Oceanic Niño Index

Timebound

Updated

1.0

1.0000000

0.7

3.1 Comments

3.1.2 What additional work would be needed for the Council to use the indicator?

[List current gaps in the indicator given the current or potentail uses listed above, what resources are needed?]

3.1.3 What issues are caused if there is a gap or delay in data underlying the indicator

[Link to management process/actions and their requirements]