[Submission]: 2023 Observation Synthesis

[khyde]

Primary Contact

kimberly.hyde@noaa.gov

Secondary Contact

nefsc.soe.leads@noaa.gov

Data Name (This will be the displayed title in Catalog)

2023 Observation Synthesis

Indicator Name (as exists in ecodata)

observation_synthesis

Family (Which group is this indicator associated with?)

• [X] Oceanographic
• [X] Habitat
• [X] Lower trophic levels
• [ ] Megafauna
• [ ] Social
• [ ] Economic

Data Description

Synthesis of multiple anomalous and extreme conditions observed in 2023 that should be noted and considered in future analyses.

Introduction to Indicator (Please explain your indicator)

Multiple anomalous conditions and extreme events were observed in 2023 that could have brief local effects and/or widespread long-term ecosystem, fishery and management implications. This section intends to provide a record of these observations, the implications they may have for other ecosystem processes, and a reflection on how they fit into our understanding of the ecosystem. Many of these observations are being actively studied but should be noted and considered in future analyses and management decisions.

Key Results and Visualization

Globally, 2023 was the warmest years on record. North Atlantic sea surface temperatures were also the warmest on record, however Northeast U.S. shelf temperatures were more variable, with near record highs in winter and near average in other seasons.

Shelf-wide Phenomena

The Gulf Stream was highly variable throughout the year, with northward shifts intermittently throughout the year and a more notable prolonged shift north along the continental shelf break in the southern Mid-Atlantic in the fall [Fig .]. This shift severely constricted the Slope Sea, the waters between the Gulf Stream and continental shelf. This shift also inhibited formation of western warm core rings and limited warm core ring interactions at the continental shelf break. The position of Gulf Stream near the continental shelf break resulted in unusually warm and salty surface waters with strong northeastward currents in the southern Mid-Atlantic in October. The warm waters are a threat to temperature sensitive species, particularly those that are at the southern end of their range or are not mobile (e.g. scallops), while also providing suitable habitat for more southern species.

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While the total number of 2023 warm core rings (18) was below the decadal average (31), there were a few events worth noting. A large early season ring moved along the shelf break and created an anomalously large shelf streamer that pulled continental shelf water into the Slope Sea. Additionally, when warm core rings interact with the shelf break, they can create biological hotspots. Hotspots can aggregate multiple species in small areas, increasing bycatch risks and marine mammal shipstrike risks. In spring 2023, concentrations of North Atlantic right whales, humpback whales, basking sharks, and other large baleen whales were observed feeding near the edge of two warm core rings that were adjacent to the continental shelf break.

Multiple fall 2023 tropical and coastal storms caused several flash flood events, above average coastal water levels, strong winds and high rainfall totals throughout the Northeast. These storms are potentially linked to the transition from the 2020-2022 La Niña conditions to strong El Niño conditions in late spring 2023. During El Niño winters, there is a noted increased frequency of East Coast storms. Storms increase the risk of coastal flooding and freshwater runoff into the coastal ocean, affect both commercial and recreational fishing, and can delay the spring transition from a well mixed water column to stratified. Increased freshwater flow decreases salinity in estuaries, reducing the amount of suitable estuarine habitat for juvenile marine fish species. In estuaries, hypoxia (low oxygen) also tends to be more severe in wet years, which negatively impacts habitat quality. The current El Niño is expected to gradually weaken and transition to neutral conditions in spring 2024.

Regional/Coastal Phenomena

There was a documented die-off of scallops in the Mid-Atlantic Elephant Trunk regions between the 2022 and 2023 surveys. In 2022, Elephant Trunk experienced stressful temperatures for scallops (17 - 19 ℃) for an average of 30 days, but ongoing research is being conducted to identify contributing factors. In summer 2023, a fish and shellfish mortality event was observed in coastal New Jersey linked to hypoxia (low dissolved oxygen) and ocean acidification.

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Summer bottom temperatures in the Gulf of Maine were the warmest on record (since 1959) resulting in the second largest bottom marine heatwave. The heatwave started in February, peaked in May and likely continued beyond August (pending data update). 2023 bottom temperature exceeded the 15oC threshold for up to 59 days along the shelf break. Data are not available yet to determine the primary source water into the Gulf of Maine nor, the impact of the fall Gulf Stream position on the bottom temperatures in the Gulf of Maine.

A wide-spread, long-duration phytoplankton bloom of the dinoflagellate Tripos muelleri generated record high (since 1998) chlorophyll concentrations that were up to ten times greater than average. The bloom was observed throughout the Gulf of Maine from March to August and extended onto Georges Bank and the northern Mid-Atlantic Bight (Fig. ). The bloom severely reduced water clarity, impacting harpoon fishing and likely affecting visual predators. Blooms of large phytoplankton species such as diatoms (20-200 µm) are a primary source of energy to the system. However, despite the size of Tripos (100-200 µm), initial observations indicate that the bloom was not grazed, nor did it sink to the bottom. The specific drivers of the bloom and implications to the food web are still under investigation.

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In Chesapeake Bay, hypoxia conditions were the lowest on record (since 1995), creating more suitable habitat for multiple fin fish and benthic species. Cooler Chesapeake Bay water temperatures paired with low hypoxia in the summer suggest conditions that season were favorable for striped bass. Cooler summer temperatures also support juvenile summer flounder growth. However, warmer winter and spring water temperatures in the Chesapeake Bay, along with other environmental factors (such as low flow), may have played a role in low production of juvenile striped bass in 2023. Higher-than-average salinity across the Bay was likely driven by low precipitation and increased the area of available habitat for species such as croaker, spot, menhaden, and red drum, while restricting habitat area for invasive blue catfish.

Implications

The implications of these events are still to be determined, but should be noted for future analyses.

Spatial Scale

NES

Temporal Scale

2023

Synthesis Theme

• [X] Multiple System Drivers
• [ ] Regime Shifts
• [ ] Ecosystem Reorganization

Define Variables

NA

Indicator Category

• [ ] Published Methods
• [ ] Extensive analysis, not yet published
• [ ] Syntheses of published information
• [ ] Database pull
• [ ] Database pull with analysis
• [X] Other

If other, please specify indicator category

Synthesis of observations

Data Contributors

Kimberly Hyde, Sarah Gaichas, Joe Caracappa

Point(s) of Contact

kimberly.hyde@noaa.gov

Affiliation

NEFSC

Public Availability

Source data are publicly available.

Accessibility and Constraints

No response

[jcaracappa1]

bottom_temp_threshold_17_19_Elephant_Trunk.png should be added to this page

[andybeet]

@BBeltz1 This needs an "indicator name" observational_synthesis?

[khyde]

I updated some of the text a bit (fixed some typos, added some hyperlinks and added a little bit of content).

Here is the link to the updated SST image with the Gulf Stream. https://drive.google.com/file/d/1ObYblh4-bCXCvIqqyJdWtpJ5qXar42Tb/view

Please update the SST caption to read: "Weekly mean sea surface temperature (October 8-10, 2023) with the long-term mean Gulf Stream position. Red lines represent the 26oC (78.8 oF) temperature contour." and add a space after the caption so it is separate from the following paragraph.

Please update the SST days caption to read: "The number of days in 2022 that exceeded the scallop stress temperature of XX" and add a space after the caption so it is separate from the following paragraph. (@jcaracappa1 what is the temperature threshold used in this plot? 18oC?)

Please update the CHL caption to read: "The chlorophyll anomaly for June 2023. Chlorophyll concentrations in the Gulf of Maine were 5-10 times greater than the long-term June average." and add a space after the caption so it is separate from the following paragraph.

Thanks!

[khyde]

Also, here is the alt text I wrote for the SST and CHL images.

CHL image alt text: A chlorophyll anomaly map from June 2023 for the Northeast shelf ecosystem showing very high chlorophyll anomalies in the Gulf of Maine and outer edge of Georges Bank, moderate above average anomalies in the eastern half of the Mid-Atlantic and moderate below average anomalies in the western Mid-Atlantic.

SST image alt text: A sea surface temperature map from October 2023 for the Northeast shelf ecosystem showing colder temperatures (12-16 degrees Celsius) in the Gulf of Maine and Georges Bank, moderate temperatures (18-22 degrees Celsius) in the western Mid-Atlantic and temperatures above 23 degrees Celsius) in the southeastern Mid-Atlantic. The Gulf Stream is almost parallel with the continental shelf break and north of the mean Gulf Stream path.

[jcaracappa1]

@BBeltz1 The temperature used in the thermal habitat gridded map are 17-19 deg C. Here's the caption for that figure in the report: "The number of days in 2022 where bottom temperature was between 17 and 19 ℃ (sressful thermal temperatures for sea scallops) in each GLORYS grid cell. The gray lines show the sea scallop estimation areas, with the Elephant Trunk region highlighted in black lines."