Dead-Zone Report Card

Compare the annual severity of Chesapeake Bay hypoxia

Each year, the Virginia Institute of Marine Science and Anchor QEA, LLC release a retrospective seasonal analysis of the severity of hypoxia in the Chesapeake Bay. The Annual Chesapeake Bay Dead Zone Report Card—one component of the Chesapeake Bay Environmental Forecast System—summarizes dissolved oxygen concentrations in the Bay as estimated by the team's 3-D, real-time hypoxia forecast model. The modeling team also generates the same dissolved oxygen statistics for previous years for comparative purposes.

Download a printable pdf copy of the VIMS 2023 report card.

Report Card Metrics

The forecast and report card use multiple metrics to quantify and compare hypoxic severity:

  • Maximum Daily Hypoxic Volume (km 3) : The maximum volume of Chesapeake Bay water experiencing hypoxic conditions on any given day
  • Average Summer Hypoxic Volume (km 3) : The average volume of hypoxic water from June through September
  • Hypoxic Duration (days): The number of days in a given year between the first and last day of hypoxic conditions exceeding 2 km 3 in volume
  • Total Annual Hypoxic Volume (km 3 days) : The total amount of hypoxia in the Bay for a given year, calculated by summing the hypoxic volume on each day
Synopsis for 2023

Relatively calm winds and warm temperatures in April 2023 resulted in hypoxia starting earlier than usual. Throughout May 2023, calm winds resulted in little mixing of the water and promoted continued stratification causing the volume of hypoxic water to further increase; however, hypoxia then remained uncharacteristically low from June until ending in late-September. As a result, even though hypoxia started relatively early, the total amount of hypoxia remained much lower than it has in many recent years. The relatively early end of hypoxia in mid-September 2023 resulted from cooling temperatures in September and strong winds associated with Tropical Storm Ophelia. Overall, even though the duration of hypoxia was near the long-term (38 year) average, the total annual amount of hypoxia and the maximum daily amount of hypoxia were quite low, indicating 2023 was a very good year with relatively favorable hypoxic conditions in the Bay.

Summed Annual Estimates

Here we describe the severity of hypoxia as estimated by the forecast model. We define hypoxia as dissolved oxygen concentrations less than 2 milligrams/Liter (mg/L).