Every American know the glorious painting by Emmanuel Leutze, “Washington Crossing the Delaware”. It is one of the most inspiring paintings of the American Revolution, showing the heroic Washington standing on the prow of a small boat crossing the ice-choked river on Christmas Day in a surprise attack on the Hessian mercenaries at Trenton, New Jersey. What strikes me, as a weather guy, is the extent to which the river in that painting was already iced over! Not just iced over, but there were small bergs in it!
I suppose that was rattling around in the back of my mind when I was working on photographs of Ice Boats No. 1, No. 2, and No. 3, operated by the city of Philadelphia. According to the City of Philadelphia’s records, “The purposes of the Trustees of the City Ice Boat(s) was to operate a vessel on the Delaware River which would be instrumental in breaking the ice during winter months and ensuring a free and open passage on the river to the Port of Philadelphia.”
The Delaware is one of our most important rivers in terms of tonnage of freight carried. It is also one of our last free-flowing rivers, with no dams or impediments. So if it ices over so badly in the winter, as early as December 25, why don’t we hear about ice breakers moving up the river to open up the ports of Philadelphia, Camden, Wilmington, and others? Because the river doesn’t ice up as badly as it once did!
In 1907, Philadelphia disbanded its Bureau of Ice Boats, established in 1837, and turned the vessels over to the Department of Wharves, Docks and Ferries. The City’s records indicate that the boats were eventually used only for dredging, ” due to the gradual disappearance of ice from the Delaware River.” Wow!
Is this perhaps a really early harbinger of human-caused global warming? Well, probably not, it seems. Washington’s crossing of the river, the inception of the Philadelphia Ice Boats, all of those really cold winter scenes we see from the 18th through early 20th centuries, are part of a climatic period called “The Little Ice Age”. One of the particularly cold periods came around 1850. Modest cooling, climatically speaking, but cooling. It is tempting to see the rapid industrialization and pollution of the Delaware Valley as the cause of this warming. My reading of the climate science, however, seems to indicate the two are unrelated. In these days of super-hot summers in so many places on Earth, many of us wish we could have a return of another Little Ice Age!