« Ecosystems Dynamics & Assessment

Current Conditions of the Northeast Shelf Ecosystem

Spring 2019 Update

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Summary of Conditions of the Northeast Shelf Ecosystem

  • During the second half of 2018, sea surface temperatures in the Northeast Shelf Ecosystem were well above average in the summer but had moderated to average levels by the end of the year.
  • Bottom temperature has increased steadily in all ecoregions of the Northeast Shelf, resulting in what appears to have been a regime shift in benthic thermal conditions in 2008.
  • The fall bloom in the Gulf of Maine and Georges Bank areas were of average dimension in 2018.
  • The fall thermal transition continues to occur later in the year in the more northern segments of the ecosystem.The area of fall occupancy habitat has expanded for the vast majority of species occurring on the Northeast Shelf, suggesting increasing temperature may be transforming habitats that were once outside the thermal tolerance of species.

Daily Sea Surface Temperature for the Second Half of the Year

Daily sea surface temperatures tended to be at or above average conditions during the second half of 2018. The largest departures from average conditions can be seen in the data for the Scotian Shelf and Gulf of Maine ecoregions (see graphs). In these plots, the current year temperatures are shown as a red line with all previous years in the dataset, starting in 1982, shown as transparent blue lines; the black line is the time series mean and the dotted lines mark plus/minus one standard deviation. From mid-year into fall, temperatures in these areas were approximately 3°C above the mean before returning to level of at or below the mean by the end of the year. In contrast, the elevated summer temperatures in the Middle Atlantic Bight and Georges Bank tended to be approximately one standard deviation above the mean before moderating to average levels.

chart showing sea surfaces temperatures on Georges Bank
Daily sea surface temperatures on Georges Bank during the second half of 2018
chart showing sea surfaces temperatures on Gulf of Maine
Daily sea surface temperatures in the Gulf of Maine during the second half of 2018
chart showing sea surfaces temperatures in the Middle Atlantic Bight
Daily sea surface temperatures in the Middle Atlantic Bight during the second half of 2018
chart showing sea surfaces temperatures on the Scotian Shelf
Daily sea surface temperatures on the Scotian Shelf during the second half of 2018

Sea Surface Temperature for the Second Half of the Year

The OISTT sea surface temperature data is based on satellite measurements and provides high spatial and temporal resolution depictions of temperature trends.  The SST conditions for the second half of 2018 were generally at above average levels in all ecoregions, however, noting that thermal conditions have moderated since the record high temperatures recorded in 2012. The Gulf of Maine, Georges Bank, and Middle Atlantic Bight SST time series appears to have two change point features, suggesting abrupt changes in temperature around 1999 and 2011 (see graph). The Scotian Shelf area has only one change point that occurred in 2008. These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. The linear trends in all the ecoregions indicate increasing temperatures; all the trends were significant.

chart showing sea surfaces temperatures on Georges Bank
Sea surface temperature time series for Georges Bank during the second half of 2018
chart showing sea surfaces temperatures on Gulf of Maine
Sea surface temperature time series for the Gulf of Maine during the second half of 2018
chart showing sea surfaces temperatures in the Middle Atlantic Bight
Sea surface temperature time series for the Middle Atlantic Bight during the second half of 2018
chart showing sea surfaces temperatures on the Scotian Shelf
Sea surface temperature time series for the Scotian Shelf during the second half of 2018

Variability in Sea Surface Temperature for the Second Half of the Year

The OISTT sea surface temperature data is based on satellite measurements and provides high spatial and temporal resolution depictions of temperature trends.  The variability in sea surface temperature conditions for the second half of year only appears to be increasing in the Gulf of Maine ecoregion (see graph); trends in all other areas were non-significant. These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. The increasing trend in the Gulf of Maine is also ecoregion is reflected in potential change points in 1987 and 2006; there were no meaningful change points in the other ecoregions.

chart showing sea surfaces temperatures on Georges Bank
Sea surface temperature variability for Georges Bank during the second half of 2018
chart showing sea surfaces temperatures on Gulf of Maine
Sea surface temperature variability for the Gulf of Maine during the second half of 2018
chart showing sea surfaces temperatures in the Middle Atlantic Bight
Sea surface temperature variability for the Middle Atlantic Bight during the second half of 2018
chart showing sea surfaces temperatures on the Scotian Shelf
Sea surface temperature variability for the Scotian Shelf during the second half of 2018

Long-term Sea Surface Temperature for the Second Half of the Year

The ERSST temperature time series provides a low-resolution depiction of sea surface temperature on the Northeast Shelf since the 1850s and is based on historical shipboard measurements, augmented with other data in recent years. The SST for the second half of 2018 was above average and generally matched the sea surface temperatures seen during the warm period of the late 1940s and early 1950s (see graph). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue.

chart showing sea surfaces temperatures on Georges Bank
Long-term sea surface temperature for the second half of 2018


Bottom Temperature for the Second Half Year

The thermal conditions at the bottom of the water column are extremely important in defining the habitats for the majority of resource species. Unlike sea surface temperatures that can be measured synoptically with satellite telemetry, bottom temperatures must be measured directly from ship surveys and other means. Thus, we often have incomplete spatial and temporal sample coverage to describe bottom temperature conditions. Recently, scientists at the NEFSC developed an interpolation approach that provides a more accurate depiction of bottom temperatures. The temperature conditions for the second half of year has been increasing significantly in all ecoregions (see graphs). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. There were change points detected in all regions around the year 2008.

chart showing bottom temperatures on Georges Bank
Bottom temperatures for the second half of 2018 on Georges Bank
chart showing bottom temperatures on Gulf of Maine
Bottom temperatures for the second half of 2018 in the Gulf of Maine
chart showing bottom temperatures in the Middle Atlantic Bight
Bottom temperatures for the second half of 2018 in the Middle Atlantic Bight
chart showing bottom temperatures on the Scotian Shelf
Bottom temperatures for the second half of 2018 on the Scotian Shelf

Fall Thermal Transition Day of the Year

Phenology is the climate influence on the timing between plant and animal production cycles. Many marine organisms time their reproductive cycles or migrations to best utilize seasonal production cycles. One measure to characterize the change in the timing of thermal forcing is the date of arrival of a fall transition temperature, which will vary by region and is meant to mark the average temperature between summer and winter. The date of arrival of the fall thermal transition temperature has been relatively constant since 1982 to approximately 2009 for the Northeast Shelf ecoregions (see graphs). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. The trend in transition day appears significant in all ecoregion with the exception of the Middle Atlantic Bight.

chart showing Fall thermal transition day on Georges Bank
Fall thermal transition day of the year for Georges Bank
chart showing Fall thermal transition day on Gulf of Maine
Fall thermal transition day of the year for the Gulf of Maine
chart showing Fall thermal transition day in the Middle Atlantic Bight
Fall thermal transition day of the year for the Middle Atlantic Bight
chart showing Fall thermal transition day on the Scotian Shelf
Fall thermal transition day of the year for the Scotian Shelf

Bottom Salinity for the Second Half Year

Salinity and temperature provide valuable indicators of the nature of source water present in the ecosystem. Salinity, in the units of practical salinity units or PSU, has increased in all ecoregions except on Georges Bank (see graphs). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. However, in all areas there appears to have been a regime shift in salinity in 2012 as salinities increase by approximately 0.5 PSU. In all areas there is the suggestion that salinity may have returned to lower levels in 2018.

chart showing Bottom salinity on Georges Bank
Bottom salinity for the second half of 2018 on Georges Bank
chart showing Bottom salinity on Gulf of Maine
Bottom salinity for the second half of 2018 in the Gulf of Maine
chart showing Bottom salinity in the Middle Atlantic Bight
Bottom salinity for the second half of 2018 in the Middle Atlantic Bight
chart showing Bottom salinity on the Scotian Shelf
Bottom salinity for the second half of 2018 on the Scotian Shelf

Weekly (8-day time step) Chlorophyll Concentration for the Second Half Year

Chlorophyll concentration tended to be at or below average conditions during the second half of 2018. In areas that typically have a fall bloom, such as the Gulf of Maine and Georges Bank, chlorophyll concentration was at the long-term mean through the bloom period (see graph). In these plots, the current year chlorophyll concentrations are shown as a red line with all previous years in the dataset, starting in 1998, shown as transparent blue lines; the black line is the time series mean and the dotted lines mark plus/minus one standard deviation. In the Middle Atlantic Bight, chlorophyll concentration was generally at average levels; whereas, the Scotian Shelf area was well below average for most of the bloom period.

chart showing Weekly chlorophyll concentration on Georges Bank
Weekly chlorophyll concentration for the second half of 2018 on Georges Bank
chart showing Weekly chlorophyll concentration in Gulf of Maine
Weekly chlorophyll concentration for the second half of 2018 in the Gulf of Maine
chart showing Weekly chlorophyll concentration in the Middle Atlantic Bight
Weekly chlorophyll concentration for the second half of 2018 in the Middle Atlantic Bight
chart showing Weekly chlorophyll concentration on the Scotian Shelf
Weekly chlorophyll concentration for the second half of 2018 on the Scotian Shelf

Chlorophyll Concentration for the Second Half Year

Chlorophyll concentration appears to have decreased in recent years in all areas of the ecosystem. The most dramatic decline appears to have occurred in the Middle Atlantic Bight where the trend is significant (see graph). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. It is noteworthy that a change point in chlorophyll concentration has been identified in all areas around the year 2012.

chart showing chlorophyll concentration on Georges Bank
Chlorophyll concentration for the second half of 2018 on Georges Bank
chart showing chlorophyll concentration in Gulf of Maine
Chlorophyll concentration for the second half of 2018 in the Gulf of Maine
chart showing chlorophyll concentration in the Middle Atlantic Bight
Chlorophyll concentration for the second half of 2018 in the Middle Atlantic Bight
chart showing chlorophyll concentration on the Scotian Shelf
Chlorophyll concentration for the second half of 2018 on the Scotian Shelf

Trends in Fall Occupancy Habitat by Functional Group

Habitat or species distribution models provide estimates of the extent of an ecosystem a particular species would likely occupy. The output of a series of these models was analyzed to determine the trends in the area of 50% probability of occurrence habitat by functional group. To ameliorate the effect of the more abundance and widely distributed species, the habitat area time series were processed with principal component analysis to provide a single index that reflects the change among all members of the functional group. The trend among benthivores, demersal piscivores, and planktovores were all significant and positive (see graphs). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue. The trend for pelagic piscivores was non-significant.

chart showing Trends in fall occupancy habitat for benthivores
Trends in fall occupancy habitat for benthivores
chart showing trends in fall occupancy habitat for demersal piscivores
Trends in fall occupancy habitat for demersal piscivores
chart showing trends in fall occupancy habitat for pelagic piscivores
Trends in fall occupancy habitat for pelagic piscivores
chart showing Trends in fall occupancy habitat for pelagic planktivores
Trends in fall occupancy habitat for pelagic planktivores

Ecosystem Forecast - Experimental Data Product

As weather and earth system models have improved, monthly forecasts over seasonal scales ranging up to seven months in advance have improved in quality. For each of the ecoregions of the Northeast Shelf, forecasts from an ensemble of seven forecast models are provided starting with the forecast estimates for June 2019 and ending in December 2019. The forecasts suggest the Northern subareas will have above average thermal conditions whereas the Middle Atlantic Bight will progressively experience less elevated temperatures (see graphs). In these plots, the mean forecasts are shown as a red line with all model forecasts in the ensemble shown as transparent blue lines; the dotted lines mark plus/minus one standard error from the mean. For more information about these forecasts, visit the North American Multi-Model Ensemble home website.

chart showing Ecosystem forecast for the June-December 2019 on Georges Bank
Ecosystem forecast for the June-December 2019 on Georges Bank
chart showing Ecosystem forecast for the June-December 2019in Gulf of Maine
Ecosystem forecast for the June-December 2019 in the Gulf of Maine
chart showing Ecosystem forecast for the June-December 2019 in the Middle Atlantic Bight
Ecosystem forecast for the June-December 2019 in the Middle Atlantic Bight
chart showing cEcosystem forecast for the June-December 2019 on the Scotian Shelf
Ecosystem forecast for the June-December 2019 on the Scotian Shelf