Current Conditions of the Northeast U.S. Shelf Ecosystem: Fall 2022 Update
A summary of temperature, salinity, chlorophyll and other conditions on the Northeast U.S. Continental Shelf during the first half of 2022.
“Current Conditions” is a biannual report on ecosystem and fisheries data for the Northeast U.S. continental shelf ecosystem. The report includes selected indicators of the physical and biological environment focusing on changes in the first half year and reflect data collected in seasonal scientific surveys. You may use this link to access archived reports.
- During the first half of 2022, sea surface temperatures in the Northeast U.S. Shelf Ecosystem continued to be well above average. A shift in thermal conditions began around 2010 with a step change of near 1°C higher temperatures in most subregions of the ecosystem.
- The spring thermal transition on Georges Bank was the earliest in the time series in 2022, indicating a transition date to spring conditions of May 14, which represents a shift of 3 to 4 weeks earlier.
- Spring phytoplankton blooms did not form in either the Gulf of Maine or Georges Bank ecoregions in 2022; however, there was evidence of winter blooms in some areas. Chlorophyll concentrations were generally below average throughout the ecosystem.
- Fish and macroinvertebrate distributions have shifted to deeper depths and more to the northeast along the coast.
Daily Sea Surface Temperature for the First Half of the Year
Daily sea surface temperatures were at or above average conditions during the first half of 2022. The Georges Bank and Gulf of Maine ecoregions had the largest departures from average conditions. Spring temperatures were approximately 2°C above the long-term average. In the Mid-Atlantic, temperatures fluctuated around the mean for the second half of the spring. In all areas except for the Mid-Atlantic Bight, temperatures moderated well above the mean by mid-year.
Sea Surface Temperature Trends for the First Half of the Year
Average sea surface temperatures for the first half of 2022 continued at high levels in all ecoregions. In Georges Bank, thermal conditions were the second warmest since the record-high temperatures observed in 2012. Spring temperatures in all areas appear to have experienced a change in level around the year 2010, increasing the mean temperature by 1°C.
The distributions of sea surface temperature by ecoregions were generally above normal. However, monthly sea surface temperature imagery shows that temperatures were below normal in the Mid-Atlantic during May. The strongest temperature anomalies were observed in Georges Bank area along its southern flank.
Trends in Variability of Sea Surface Temperature for the First Half of the Year
Sea surface temperature variability (the standard deviation within each ecoregion) for the first half of 2022 increased in the more northern Northeast Shelf ecoregions. The increase in variability appears to be significant in the Gulf of Maine and Scotian Shelf but not significant in the other areas. There were no clear-cut patterns in any change points in variability between areas.
Long-term Trends of Sea Surface Temperature for the First Year
We derived the long-term temperature time series from the Extended Reconstructed Sea Surface Temperature dataset. It provides a low-resolution depiction of sea surface temperature on the Northeast Shelf since the 1850s. The data is based on historical shipboard measures and augmented with other data in recent years. The temperature for the first half of 2022 was above average and was among the highest values in the data time series.
Spring Thermal Transition Day
Phenology is the seasonal timing of plant and animal production cycles. Many marine organisms time their reproductive cycles to make best use of seasonal phytoplankton blooms, such as the spring and fall blooms. In turn, temperature plays a role in the development of blooms. The initiation date of the spring transition temperature, which varies by region, is likely related to different forcing factors. The spring thermal transition date was relatively constant from 1982 to approximately 2010 for the Northeast Shelf ecoregions. A change point appeared in the northern areas around 2010, when the transition date advanced by approximately two weeks. In recent years, the trend toward earlier spring transition dates appears significant in northern segments of the ecosystem—the Gulf of Maine and Scotian Shelf ecoregions, noting that the 2022 spring transition in the Georges Bank was the earliest in the time series.
Weekly Chlorophyll for the First Half of the Year
Phytoplankton blooms, measured as chlorophyll concentration, are a major component of the food web. They are a primary food source for zooplankton and filter feeders such as shellfish. Chlorophyll concentration was generally below average during the first half of 2022. In areas that typically have a spring bloom, such as Georges Bank and the Gulf of Maine, chlorophyll concentration varied below the long-term average through the bloom period. The chlorophyll concentration for the Middle Atlantic Bight and Scotian Shelf also tended to be below the long term mean.
Chlorophyll Concentration Trends for the First Half of the Year
Average chlorophyll concentrations during the first half of the year appears to have decreased in recent years in all subareas of the ecosystem to a low point in 2019. With the exception of the Scotian Shelf, the declining trends were significant. In the Gulf of Maine and Scotian Shelf, chlorophyll concentrations appear to be increasing in recent years. It is noteworthy that we have identified a change point in chlorophyll concentration in all areas within the last decade or so.
Fish Distribution from Spring Survey Data
- The distribution of Northeast Shelf ecosystem species have changed over recent decades. Individual species have shifted distribution for numerous of reasons, and these shifts can be characterized in a number of different ways. Three metrics have been used to characterize species distribution on the Northeast Shelf:The position in the ecosystem along an axis oriented from the southwest to the northeast referred to as the along shelf distance. Along- shelf distances range from 0 to 1360 km, which relates to positions along the axis from the origin in southwest to northeast.
- The depth of occurrence, which ranges from 0 to -260 m The distance from the coastline, from 0 to 110 km
These indices are based on 48 of the most abundant taxa. Along-shelf distance has increased over time, reflecting a shift in species distribution to the Northeast; the 2022 distance was the second highest in the time series. Depth of occurrence has also increased over time, reflecting a greater use of deeper habitats. There is no significant trend in distance to the coastline. The map position of the center of gravity for these species was at its second most extreme northeastern position in 2022, east of Nantucket Island, in contrast to the first point in the time series 1968, which was well to the south and west.