Friday, November 4, 2011

King Tide: The Mightiest of All Tides

The king tide nearly washed over the bridge in Wickford R.I.
To view more photos of the effects of the
king tide in R.I. click here.

Do you live by the shore?  During the past week did you notice a significant rise in sea level?  If so, what you witnessed was most likely the result of a king tide.  The term “king tide” refers to a remarkably high tide.  This king tide – like all others – offers us a preview of what our coastlines will look like as the sea level rises.  To put things in perspective, mean high tide in Newport, Rhode Island is generally measured at 3.6 feet; however, during a king tide, this level can rise to 5.2 feet. Not only have high tides been extremely high in the past two months, but the rate at which sea level rises has been increasing over the past 100 years.  Because of this, our coastlines are being inundated with more salt water. And areas at or below sea level are experiencing more flooding than they have in the past.

Like all tides, the king tide is influenced by the relationship of the distance between the Moon, Sun, and Earth.  During its 28-day cycle around the earth, the moon’s gravitational pull exerts a significant force on the oceans.  When the moon and sun are in a parallel line with the earth, the gravitational pull of the moon and sun create spring tides. These are the stronger tides we see during the full and new moon phase. When the earth is in between the sun and moon—a new moon—the spring tide is lower than when the sun and moon are on the same side of the earch. However, when the moon is perpendicular (90ยบ) to the line of the sun and earth, we experience weaker tides, known as the neap tides.
The tidal cycle during a lunar month.

Although the east coast experiences two high and two low tides every day, the height of the tide changes each time. We experience two spring tides each month (during the full and new moon) but a king tide only comes along twice a year. The summer king tide generally tends to take place during the day while the winter king tide most often occurs at night, which garners it less notice. However, this year the king tide also occurred during sunlight hours, raising more awareness of the potential effects sea level rise will have in the coming century.  To be more exact, this year, in North Kingstown, the king tide took place on October 26, 27, and 28 at 7:46AM, 8:37AM, and 9:28AM, respectively. 

The Phrase King Tide originated in New Zeeland, Australia and other Pacific nations, possibly because they experience greater effects from tides due to their location in the vast open Pacific Ocean. The island nation of Tuvalu is also located in the middle of the Pacific and is made up of low-lying atolls that has been extremely affected by the combination of king tides and sea level rise. 

Here in New England the king tide was easily seen and impacted many coastal areas. In Rhode Island, citizens were invited to post photos on the R.I. Sea Grant Facebook page of the effects of this tide. Perhaps the most remarkable photos were those that displayed the disparity between low and extremely high tides (from a king tide) in Wickford, Jamestown, and along the Pawtuxet River, among other locales.

On Long Wharf in Boston, MA the king tide actually covered much of the wharf and flooded the streets.Watch the video above to see what the Wharf looked like on October 28th.

While king tide – along with its high and strong waves in the summer – may attract many adventurers, it is a force not to be reckoned with, as its strength can be deadly.