Delaware Estuary: Climate changes have already occurred

Climate change has been steadily altering the weather in the Delaware Estuary, and scientists have documented it.

The changes were one of the presentations at a three-day science and environmental summit hosted by the Partnership for the Delaware Estuary.

One of the things that surprised me most in the presentation by Raymond Najjar, a professor of oceanography and climate change expert at Penn State, is that wind speeds in the estuary are declining.

"We see this throughout the seasons," Najjar reported.

Scientists think they have an explanation: Increasing development and other changes in land use. Basically that increases the land "roughness," which slows the wind.

Other changes, some not so surprising:  Since 1910, monthly temperature averages have increased. And in the past 30 years, they have increased more sharply.

Precipitation has increased - mostly during the fall season. The number of days with temperatures that fall below 32 degrees Fahrenheit has decreased.

There has been a "significant" increase in the number of days with precipitation amounting to more than 4.5 centimeters. That, of course, affects flooding. Looking at the six biggest floods of the last 100 years, half of them have occurred in the last 15 years.

One oddity: The number of days with temperatures above 90 degrees has not increased, but Najjar said factors other than climate change were the cause.

Researchers also have looked at snow cover in the basin, and found no significant long-term trend, many oldsters' memories of snow-bound winters aside. He and others think this may be related to a climactic phenomenon known as the North Atlantic oscillation. Basically, it's fluctuations in atmospheric pressure, and it affects winds and storm patterns.

The oscillation also may be affecting the "storminess" of the estuary. Researchers have tallied the number of days per year with mean barometric pressure below 1000 millibars at Atlantic City -- low pressure being an indication of bad weather. They have found lots of year-to-year variability, Najjar said, but no long-term trend.

Sorting out all the influences is difficult. But one thing is clear, Najjar said. "The atmosphere is fundamentally different than it was 30 years ago."

Climate change and other "indicators" of what's happening in the estuary -- to its water quality, water quantity, fish, shellfish, forests, marshes and more -- is in a recent "State of the Estuary" assessment.  A 15-page report is backed up by a large technical report, and both are worth perusing. You can see them here.

"The take-home message is that while we have some things we can be proud of, some things are areas of concern," said Danielle Kreeger, the partnership's science director. Taken together, the researchers graded the environmental conditions of the estuary as "fair."

But note this: The human population is predicted to increase 80 percent by 2100. "The natural resources will, on balance, be increasingly taxed by these changes," Kreeger said.

The summit, being held at the bottom of the estuary, in Cape May, draws together scientists, researchers, policy-makers and others from throughout the region to discuss the latest research and hottest topics.  It is held every other year.

This year's focus is a clear nod to climate change -- "Weather Change - Shifting Environments, Shifting Policies, Shifting Needs."

You can find more information and, in time, the powerpoint presentations, at www.DelawareEstuary.org.