December 2007

Ready-to-Use News Articles

Mysterious Ancient Lands below Confederation Bridge

By Nancy Macdonald

When I look over the side of Confederation Bridge, I see crashing blue waves with white caps. When marine geoscientist John Shaw looks over the bridge he sees so much more. For him, Kevin Costner’s film “Waterworld” is a reality, with its scenes of rising ocean waters inundating and preserving the ancient landscape as it was 10,000 years ago.

John Shaw, a sea level researcher with Natural Resources Canada (NRCan), explains how he pulled back the water column to discover ancient rivers, lakes and undulating land that once connected New Brunswick to Prince Edward Island.

“Sea level change is fascinating,” he explains. “It is generally dependent on two factors: the speed that ice at the poles is melting or freezing (as would have been the case 20,000 years ago) and the rate that the land is rising.”

Rising land sounds like a strange occurrence but is quite common. When glaciers were present, they weighed so much that they pushed the land down; as they melted, the land started to go back up. Today, we are still experiencing the rebounding effects from these ancient glaciers For example, land near the Gulf of St. Lawrence has been rising, while land near Sable Island in Nova Scotia has been lowering (Sable Island was not covered by the ancient glacier and had been pushed up during the glacial period). Coupled with increasing water levels from melting polar caps, sea level change is a very dynamic and interesting system to study.

“To get an overall picture of what sea level was doing in the Atlantic during the last 10,000 years, NRCan and the Department of Fisheries and Oceans conducted coastal monitoring and mapped the bottom of the ocean floor of the Northumberland Strait using multibeam bathymetry,” John explains. Multibeam bathymetry consists of a series of sound beams that are reflected off the ocean bottom. This reflection data is collected and processed to show water depths and, ultimately, the three-dimensional contours of the ocean floor.

Today, the sea floor is swept by tidal currents. But 9,000 years ago, the sea level was lower, and the Northumberland Strait was occupied by rivers and lakes. Some of these lakes were 20–30 meters deep. It wasn’t until 6,000 years ago that the rising sea level flooded the Strait, creating the island we now know as Prince Edward Island. Today, Northumberland Strait continues to expand, and Prince Edward Island is becoming more and more isolated from the main shore. The sea surrounding PEI is rising by 32 cm per century, as measured from a gauge located in Charlottetown in 1911.

The Bedford Institute of Oceanography has created models of what the Northumberland Strait looked like 9,000 years ago. “The models give you an inkling of how much the area has changed in a very short period of time,” says John.

Photo and Caption

Please note that the photo is available in higher resolution upon request.

Multibeam imagery of the ancient rivers and lakes that lie underneath the water column of the Northumberland Strait.