Suspended matter that is introduced into the water at Providence, if it is not washed up on the beach, will move slowly to the ocean 23 nautical miles to the south. It can take from 42 to 59 days for the journey, the amount of time physical oceanographers estimate Narragansett Bay needs to flush itself and exchange its waters. That's mighty slow traveling, and yet it is movement enough to enable the Bay to renew its stock of salty ocean water, mix it with the freshwater runoff from the land, and spread a nutrient repast for trillions of tiny creatures, which in turn provide sustenance for multitudes of others.
While the overall replacement of Bay waters proceeds at a deliberate pace there are all sorts of other, far more rapid movements. The tides work ceaselessly, ebbing and flooding twice a day, and set up powerful currents in constricted channels (as every Bay sailor knows who has ridden the surge past the old Stone Bridge in Tiverton two or three hours before slack water or who has tacked out of Newport Harbor with the wind from the south and a strong tide running into the mouth of the East Passage).
Wind waves move across the surface, their heights dictated by the power of wind, the state of the tide, and the amount of open water or "fetch" available to the wind to do its work. More often than not, a "chop" will arise in the Bay on a summer afternoon. The waves are low and close together, uncomfortable for the small boat operator but of no particular consequence. The huge swells of Rhode Island Sound, often representing energy transfer from great distances at sea, are not possible inside Narragansett Bay because the protective arms of land block the ocean surge and dampen the effects of many winds. Boatmen say there are few days in the warm weather months when it is not possible to sail or power about in relative comfort.
There is another kind of "chop" present in the summer months on Narragansett Bay, especially in its broad upper reaches, regardless of wind or tide. The wakes of hundreds of power boats, large and small, keep the surface in motion even in a dead calm. If everybody motored in the same direction, steady, almost rhythmic wave action would wash the beaches on opposite shores. This happens along the Providence River, where the traffic generally moves north and south. But once in the open there is no pattern and wakes intersect and collide. Water movement is lumpy without recognizable design; the opposing forces of energy tend to neutralize each other.
In some open stretches, the water of the Bay can get downright rough on occasion. Strong winds from either north or south can build up substantial seas in the upper Bay between Conimicut Point and Prudence Island. The entire West Passage can be nasty, from ocean to the Providence River, under certain wind conditions, and the Sakonnet River can get lumpy too. Hurricanes of course are in a class by themselves. When they hit, the Bay becomes a big funnel, constricting and mounding up the hurricane surge. Even the shores, which normally dampen wind velocities, can't help when the winds roar at 75 to 100 miles an hour. At these times humans leave the, Bay to its own devices, haul out their boats or let them ride on lengthened and rein; forced lines at sheltered moorings.
From 1635 to 1938, nine severe tropical storms affecting the Bay region were recorded. An account of the earliest was written by Governor Bradford of the Plymouth Colony. In 1815 a "great gale" struck Providence, with water levels 12 to 14 feet above normal. The Weybosset Bridge, connecting the two sides of the town, gave way Under the impact of vessels torn from their moorings, and "vessels, lumber, buildings, and property of every description, in one crowded mass, were hurled with great velocity up the Cove. Thirty-flve vessels, including four ships, nine brigs, seven schooners and fifteen sloops have been enumerated on its shores." Many residents fled from their flooded homes and sought refuge on the hills, and 500 buildings were destroyed.
In modern times the great storm of September 21, 1938, striking in the late afternoon, the hurricane of September 14, 1944, arriving at night, and Hurricane Carol of August 31, 1954, roaring in during the morning hours, have been etched in the memories of thousands of persons who live along the shores. The hurricane of 1938 caused 262 deaths and 8100 million in property damage. The 1944 storm toppled thousands of stately trees, blocking roads for days, but the low tide factor reduced damage from flooding. In 1954, the state was again caught with few defenses, but shorefront residents, wary now, quickly fled to safety and only 19 lives were lost. Today massive hurricane gates are closed at Providence when a hurricane approaches, and waterfront property owners take precautions. National Weather Service warnings are more frequent and accurate. Loss of life should never be high in future storms.
The prevailing winds of Narragansett Bay blow from the northwest in the winter and from the southwest in the summer. The summer breezes, when the temperature is high, are often light and variable in the morning hours, then steady and even brisk from the south to southwest during the afternoon, dying off to a flat calm in the evening. Boat owners can judge, frequently with considerable accuracy, when the afternoon "sea breeze" will arrive from the south, especially if several days of really hot weather have occurred. At these times the heated land sends hot air aloft, creating an updraft which pulls cooler sea breezes inland. A substantial air movement from off the ocean becomes the afternoon "sea breeze." As the sun goes down, the thermal engine slows and the winds die back to zephyrs.
Roger Williams, the founder of the Providence Plantations, was an accurate observer of such things. In 1643, he wrote:
[The southwest wind] is the pleasingest, warmest wind in the Climate, most desired of the Indians, making faire weather ordinarily; and therefore they have a Tradition, that to the Southwest, which they call Sowwaniu, the gods chiefly dwell; and hither the soules of all their Great and Good men and women goe.
This Southwest wind is called by the New-English, the Sea turns, which comes from the Sunne in the morning, about nine or ten of the clock Southeast, and about South, and then strongest Southwest in the after-noone, and towards night, when it dies away.
It is rightly called the Sea fume, because the wind commonly all the Summer, comes off from the North and Northwest in the night, and then fumes againe About from the South in the day: as Salomon speaks of the vanitie of the Winds in their changes, Eccles. 1-6.
When the days are exceptionally hot and substantial amounts of moist sea air are pulled into the thermal column, striking cloud formations such as thunderheads can occur, with savage rain squalls and rushing 40- and 50-knot winds that move opposite to the prevailing direction. At such times, wary boatmen seek shelter or drop their sails. Usually these squalls last no more than a few minutes and then the familiar pattern is reestablished.
The "sea breeze" keeps the urban communities of the upper Bay four to five degrees cooler in the summer than the communities inland, and provides even more substantial relief from the summer heat to settlements at the mouth. The temperature of the water also has a beneficial effect on the climate, giving off stored heat in the fall at a slower rate than the land; in effect extending the season for shore dwellers.
Water temperatures, like other physical characteristics, have been measured at numerous points around the Bay with great accuracy and over extended periods of time. Steacy Hicks, a physical oceanographer who many Rhode Islanders remember as the designer of a system for making wave-height forecasts at the ocean beaches, did considerable work in describing the Bay's physical features during the fifties. He found that in general summer surface temperatures range from highs of about 74° F to lows of 64° F at the mouth. Bottom temperatures are progressively colder, as much as six to eight degrees colder 15 feet below the surface. Although just right for swimming, the Bay's waters force scuba divers to wear wet suits even in summer. Winter water temperatures are more even, from surface to bottom reaching a low in February of about 36°F to 38°F, except for unusually severe winters when surface water can freeze, especially in sheltered coves and inlets. Rhode Islanders can look back on the winter of 1976-77 to recall a time when all of Greenwich Bay was frozen and large sections of the Providence River as well. Quahaug fishermen, their boats frozen in at the docks, walked across the ice, sawed out narrow trenches through the frozen surface of the Bay, and dug out the bivalves with bullrakes, like so many farmers hoeing their crops. There have been other hard freezes through the history of the state. In 1779-80, well-traveled paths were marked across snow-covered ice between settlements on one side of the Bay and the other.
Most winters the Bay is open, and winter sports people must look elsewhere for amusement. Saltwater ice is formed far slower than freshwater ice and only under prolonged low temperatures. The tides and currents slow the process and the saline content of the water reduces the freezing point. Thus, the more brackish and less exposed coves freeze first.
Scientists measure the salt content of tide water in parts per thousand. Salinity not only increases buoyancy for those whose swimming consists of floating lazily at the surface like ocean sunfish but also has much to do with the kinds of plants and animals that live beneath the surface. The Bay is salty but not overly so, becoming more and more brackish toward its head, where rivers and streams provide a freshwater mix. The Blackstone, Woonasquatucket, and Moshassuck at Providence, the Palmer River in Barrington, the Taunton at the head of Mount Hope Bay, the Pawtuxet marking the boundaries of Cranston and Warwick, and the Potowomut River in North Kingstown all play a part in reducing salinities in adjacent waters. At its entrances and for a considerable distance upward, the Bay contains water with salt content of 30 to 32 parts per thousand. The proportions drop off dramatically inside the river mouths. Bottom waters are generally more salty than the water at the surface, and the water of the East Passage is the saltiest of all.
Variations in salinity once were of great importance to Rhode Islanders. Oystering was big business and oysters grow best in a somewhat brackish environment (oysters can tolerate salinities of from 3 to 40 parts per thousand and temperatures of from 33° to 84° F). The productive oyster transplant grounds, when seed oysters from Long Island Sound and Virginia were shipped into the Bay and millions of pounds were harvested annually, were in the upper Bay. In 1880, A. Howard Clark, in a report on the fisheries of Rhode Island, said, "In former years beds grew naturally clear up to the city of Providence, and oysters were even found in the 'Cove' (now filled land), that pretty circle of water near the railroad station, the banks of which have been converted into a park. Now, however, any leases of ground north of Fields and Kettle Points is unpracticable and prohibited because of the large amount of umpurities thrown into the water by the city's drainage."
Today the oysters are gone, and shellfishing of any kind, other than authorized transplant programs, is prohibited from the head of the Bay to a line south that extends from the Warwick light to Providence Point on Prudence Island and then to the tip of Popasquash Point in Bristol.