Phenology, Winter, and Cherry Blossoms

Phenology is perfectly captured by the cherry blossoms in D.C.

Phenology is perfectly captured by the cherry blossoms in D.C. Credit

Over the next few months, you will probably read a few posts on the topic of phenology.

Phenology is sometimes referred to as “the science of appearance” and is used to describe the timing of seasonal events. We experience phenology every year in Chesapeake Bay, including the date when leaves start to change color in the fall, or when birds migrate south for the winter, or when spring peepers create their chorus.

If you live in the D.C. area, you can check out one of the world’s most popular phenology events: the cherry blossoms! The annual festival started yesterday, and made the news last week when peak bloom dates were moved up by two weeks due to the mild winter and where threatened by a cold snap.

Why we care?

Spring peepers are a quintessential sound of spring across the Eastern US. credit

Spring peepers are a quintessential sound of spring across the Eastern US. credit

The timing of these events are largely triggered by environmental cues including temperature, precipitation, and sunlight changes. For example, blue crabs move to deeper waters to burrow for the winter when water temperatures start to dip below ~50°C.

So the question on my mind: how will climate change affect phenology?

Let’s look at some data!

In last week’s post, we looked at a plot that suggests the length of winter is shrinking in Chesapeake Bay.

Figure 1: The winter TXx index is the warmest temperature reached each winter.

Figure 1: The winter TXx index is the warmest temperature reached each winter.

Today, we are going to look at two climate indices (TXx and TNn) to investigate if has winter warmed.

TXx is the absolute warmest temperature reached each winter. So think about that overall warmest day in the winter and ask yourself, is that day getting warmer?

The answer is yes! Over the last century, that warmest temperature reached each winter is now 1.7°C warmer (Figure 1).

TNn is the absolute coldest temperature reached each month and that value has also increased. In other words, the coldest day each winter is getting less cold. Over the last century, that coldest day in winter is 2.3°C warmer (Figure 2).

Figure 2: The winter TNn index is the coldest temperature reached each winter.

Figure 2: The winter TNn index is the coldest temperature reached each winter.

Something that is interesting to note, that colder temperature has increased at a faster rate than the warmest temperature.

Next Steps

So, that warmest day each winter is now a bit warmer and that coldest day is also a bit warmer. This could certainly affect phenology as well as the environmental range of organisms. But a key to remember, variability is always present!

What I mean: while the maximum and minimum temperature reached each winter is likely to be warmer in years to come, we can still very really cold winters!

More to come!

 

Kari Pohl

About Kari Pohl

I am a post-doctoral researcher at NOAA and the University of Maryland (Center for Environmental Science at Horn Point Laboratory). My work investigates how climate variability and extremes affect the diverse ecosystems in Chesapeake Bay. I received a Ph.D. in oceanography from the University of Rhode Island (2014) and received a B.S. in Environmental Science and a B.A. in Chemistry from Roger Williams University (2009). When I am not busy being a scientist, my hobbies include running, watching (and often yelling at) the Boston Bruins, and taking photos of my cat.
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