Global Sea Level Rise: Updated

It’s been a year since I posted my sea level rise animation, so it’s time for an update!

…Yup, it’s still rising.

The year-to-year difference isn’t quite as big for 2016-2017 as for 2015-2016. I suspect the jump in 2016 was caused by the monster El Niño of the previous winter.  Since we’ve had weak La Niña conditions this past winter, this could account for the smaller increase so far this year.

GMSL 2017
Global average sea level since 1880. Data composited from CSIRO (1880-2013) and satellite observations (1993-present). Anomalies are measured relative to the 1880 minimum.

Research Poster

If you want a not-too-technical introduction to the current state of my research, check this out.

I made this poster for an event at Boston College tomorrow. The goal: introduce freshmen in an introductory climate class to an area of active climate research (and recruit interested students for our lab).  I swapped the jargon/technical details for field photos. After all, scuba pictures capture students’ attention in a way no graph can!

PDF research overview

Raindrops keep falling on my head

Tropical cloud-watching never gets old.  Near the equator, the warm ocean generates a ton of fuel for cloud growth.  Over the course of a few hours, you can watch a small cloud grow into a tower tens of thousands of feet tall.  If you look at satellite images of the Pacific, you’ll often see a band of these clouds just north of the Equator.  That band is called the Intertropical Convergence Zone (ITCZ), which I’ve discussed before, and is the pillar of global atmospheric circulation.

Rainbow in the Marshall Islands
A developing storm brings a rainbow to the Marshall Islands. (photo by Diane Thompson)

The seasonal movement of the ITCZ over the Marshalls provides the country’s drinking water.  Needless to say, it’s pretty important; when it’s too far from the Marshalls, wells and catchments run dry.  However, it’s hard to simulate the ITCZ accurately in climate models, which makes its future behavior difficult to predict.  As a first step, though, we can look at how its location and strength has changed in the past.

Unfortunately, I haven’t found many good visualizations of the ITCZ through time, so I made my own.  This video shows monthly precipitation from 1979 through 2016, from NOAA’s Global Precipitation Climatology Project (GPCP).

Brief rant: Mapping the Pacific is hell.  Most files and programs pretend that the world ends at the International Date Line, which runs smack-dab down the middle of the Pacific.  So, when I tried to map the Pacific Islands, everything beyond the date line simply didn’t exist, and it took nearly a week to fix it.  The result, though, is worth it, because I can finally generate plots that show the outlines of the oft-ignored Pacific Islands and reefs!

What climate patterns can we identify here?

Continue reading Raindrops keep falling on my head

Visualizing Sea Level Rise in the Marshall Islands

A best-case scenario for sea level rise over the next ~100 years.
An optimistic scenario for sea level rise over the next ~100 years (pen & ink, colored in GIMP because Photoshop ain’t cheap).

In the past few weeks, I’ve been reading this book on climate change and tradition in the Marshall Islands, and it’s yielded some interesting quotes on how the Marshallese perceive sea level rise.

For example, when asked what would happen if the Marshall Islands are submerged, one resident had a simple solution:

“Float!”

It’s a funny answer, but it masks the nervous uncertainty that many Marshallese people share about their future.  In the coming decades, the rate of sea level rise will depend on how aggressively we mitigate our carbon emissions, so estimates of future sea level rise can vary.  Some Marshallese imagine a future in which the ocean engulfs the tops of their palm trees.  That’s a bit extreme: most estimates put sea level rise between 0.6 and 1 meter by 2100.

At the other extreme, there’s a widespread misconception (debunked here and in my animation here) that sea level rise isn’t accelerating, or, wronger still, that it isn’t rising at all.

These misconceptions led me to dig through the tide gauge records on Kwajalein Atoll, available here:

asdfasdfasdf
Monthly mean sea level for Kwajalein Atoll in the Marshall Islands.  Between 1946 and 2015, sea level rose by 2.2 mm/yr (±0.82 mm/yr), but that rate is accelerating.

Some observations: 1) Sea level is rising.  2) There are sudden but temporary dips in sea level, in 1983 and 1997 for example.  These drops in sea level match El Niño events.  For the same reason, sea level dropped in 2015, but has since risen back up to pre-El Niño levels.

Sea level rise will continue to accelerate in the next century, reaching ~0.4 meters by 2100 (compared to 1986-2005) in the very best case, but more likely between 0.6 and 1 m.

Is that enough to put the Marshall Islands under water?

Continue reading Visualizing Sea Level Rise in the Marshall Islands

Global Sea Level Rise

GMSL
Global average sea level since 1880 (compared to 1995).  Data composited from CSIRO (1880-2013) and satellite observations (1993-present).

Even though the rate changes, sea level is clearly rising.  It’s already about a foot higher than in 1880, and is expected to rise by up to a meter by the end of the century (if melting of polar ice sheets accelerates, this number could be much higher).  This figure was inspired by Dr. Ed Hawkins’ now-famous climate spiral, and took advice from this talk on making beautiful figures.

This is What Sea Level Rise Looks Like

Long Wharf king tide

Boston’s Long Wharf is flooding.

This flooding is part of a “king tide” – a tide higher than all others.  When the sun, moon, and Earth are in alignment, and close to each other, the tides will have especially high amplitudes – that is, the highest high tides and the lowest low tides.  If you want a general introduction to how tides work, check out this Crash Course Astronomy video.

So, with this week’s supermoon, the tides are especially strong – some of the strongest of the year.  During high tide, salt water is sneaking through storm drains and spilling over seawalls all along our coasts.

This kind of flooding is often called “nuisance flooding” or “clear-day flooding” because it isn’t associated with storm surges or winds.  But let’s be clear: this “nuisance flooding” is exactly how sea level rise works.

What’s more, these floods will become more common as sea level rises.

Continue reading This is What Sea Level Rise Looks Like

Massachusetts Oceanography and the Impacts of Drought

In the deserts of Arizona, I always talked about oceans the same way that we might talk about unicorns: It’d be nice to see one, but good luck with that.

Going to grad school in New England means I finally have an ocean within walking distance of my office.  So, between SCUBA and oceanography courses, I’m taking every chance to learn more about the Atlantic.

Boston University has partnered with the Stellwagen Bank Marine Sanctuary to use the Research Vessel Auk to collect seawater and plankton data around the Sanctuary (a rectangular area stretching roughly from Cape Cod to Cape Ann).  I know the phrase “collect data” can sound inherently boring, so here’s a whale picture to convince you that it’s actually fascinating:

We had a "whale" of a time watching these humpbacks feeding!
We had a “whale” of a time watching humpbacks feeding!  There are actually three whales in this picture.  Together, they dive, blow a wide ring of bubbles to corral fish, then emerge from the water with their mouths agape, netting as many fish as possible.  I’ve heard that this behavior, called “bubble netting”, wasn’t seen in Stellwagen Bank until a few years ago.  This implies that bubble netting is a behavior these whales picked up from other whales, like a kind of cultural exchange.  Basically, whales are smart.

Continue reading Massachusetts Oceanography and the Impacts of Drought