Ecosystem Targets and Supporting Indicators

Water Temperature

Long-term annual water temperatures from 1960-2020, measured from multiple locations throughout the Long Island Sound.

Near Surface Water Temperature in Niantic Bay
WinterSpringSummerFallAnnual Mean
19763.9211.1418.949.6810.90
19771.2910.4319.6111.4910.84
19781.929.4018.9112.1210.64
19793.1210.6719.9312.3311.57
19803.4510.5319.6110.6811.10
19812.3510.6920.1010.7011.01
19822.279.8819.7012.4611.13
19834.6210.8719.6112.6111.98
19844.2810.9819.6712.8411.97
19853.6310.9920.2212.8511.98
19864.0411.5219.4212.3811.89
19874.3611.5619.6511.3211.78
19883.2710.7919.1611.1711.12
19893.8010.6819.7310.9811.34
19904.2810.8319.8913.1112.07
19915.3612.3320.0012.4312.57
19924.4310.9819.0811.1911.45
19933.7711.0319.9111.8511.69
19942.5210.6520.1212.8811.60
19955.2811.3620.2612.8812.50
19962.859.7118.7410.8910.58
19973.699.8518.8211.0410.90
19984.6411.5319.9912.2012.14
19994.9512.5520.8613.1512.92
20004.1611.7720.4412.3912.22
20014.2511.5420.4613.5412.53
20025.6511.9720.8312.0912.67
20032.3710.5020.3312.4011.46
20043.1711.5519.9812.0711.72
20053.2011.0320.2712.5311.81
20065.6912.0620.4713.7513.04
20074.9311.2920.2513.2512.49
20085.3511.9420.6712.5112.65
20094.0411.4319.9212.0511.91
20103.7913.0420.8211.5612.36
20112.9911.3020.4213.4412.10
20127.2013.8121.9113.0314.01
20134.6211.9621.1812.9212.72
20143.4211.4020.5812.5612.04
20152.1711.2722.2014.3612.57
20165.9812.0721.4012.8913.11
20175.1111.9920.0813.2212.65
20183.8011.5221.6212.4712.40
20194.8912.2821.3412.9212.91

WHAT IS THE WATER TEMPERATURE INDICATOR?

We use several water temperature datasets, located throughout the sound, to improve our understanding of decadal and long-term changes in water temperature – averaged 17 stations representing soundwide by CTDEEP, Niantic Bay by Millstone Environmental Lab, Milford by NOAA Milford Lab, and Woods Hole by Woods Hole Oceanographic Institute. It is important to track water temperature as changes can significantly impact biological, chemical, and physical components in Long Island Sound. For example, increases in surface water temperatures have been linked to observed changes in the fish community – as cold-adapted fish (e.g., alewife, Atlantic cod, and winter flounder) have been observed less frequently in recent years, while warm-adapted fish (e.g., striped bass, black sea bass, and summer flounder) have been observed more frequently. Furthermore, increases in bottom water temperature also have an affect on the benthic community. For example, American lobsters cannot maintain their metabolisms in waters above 20°C for long periods of time and therefore have declined significantly in recent years. Additionally, these changes in fish community can have cascading effects up the food web, where the prey of these species are changing in assemblages, as well. Seasonal increases in water temperature can also impact different life stages of fish, shellfish, crustaceans, and zooplankton, and therefore may hinder their success in growth. These changes are believed to be indicative of climate change implications.

Here we report on both long-term annual and winter water temperatures to show us relative temperature change at several stations throughout the region over time. It helps us see the decade scale-up and downswings in the regional data, as well as the overall year to year variability. We also included winter temperatures because it is less impacted by daily weather patterns and station locations, and therefore stays pretty uniform temperature throughout the Sound. The other dataset shows soundwide seasonal bottom averages. This dataset is much shorter, but higher resolution. By clicking the individual seasons on or off in the legend, you can more clearly see the patterns within each season.

HOW IS THIS TEMPERATURE DATA COLLECTED?

The long-term annual and winter graphs show several longer datasets from throughout the region. In most cases, these measurements are taken at least weekly from near-surface inshore waters in the vicinity of various laboratory facilities. The seasonal bottom water temperature dataset is collected by CTDEEP from 17 stations located throughout the Sound through the Long Island Sound Water Quality and Hypoxia Monitoring Program.

STATUS

Both long-term annual and winter datasets are increasing at all stations. When all stations are averaged, from 1960-2020, the annual water temperature has increased by 11.27 percent, while the winter water temperature has increased by 15.24 percent. Likewise, seasonal bottom water temperatures have been slowly but steadily increasing throughout the Sound – from 1991-2020, winter has increased by 3.75 percent, spring by 4.39 percent, summer by 3.39 percent and fall by 4.58 percent. The overall mean from 1991 through 2020 is 37.21°F for winter, 49.08°F for spring, 67.87°F for summer, and 57.87°F for fall.

DATA NOTES

Our various regional datasets used for this indicator are sourced from the following agencies/organizations:

  • Soundwide dataset is from the averaged 17 stations throughout the Sound conducted by CTDEEP
  • Niantic Bay is conducted by Millstone Environmental Lab
  • Milford is conducted by NOAA Milford Lab
  • Woods Hole is conducted by Woods Hole Oceanographic Institute

Winter defined as January-March, spring as April-June, summer as July-September, and fall as October-December.

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