I wrote this clip for the Bangor University School of Ocean Sciences Alumni Newsletter, “The Bridge” (November 2019). One of the requirements was to provide a picture of a local bridge.
In Twenty Years
My undergraduate study at Bangor in Ocean Science (1992-1995) set me up well for my PhD in satellite oceanography. My mission was to intercalibrate two satellite altimeters (Geosat and TOPEX / Poseidon) to derive a long-term data set of global sea surface heights.
Geosat was launched in 1985 when satellite altimetry was a relatively new technology but it wasn’t the best data to be working with. Today, many consider the quality of Geosat data to be too inaccurate for meaningful sea level studies and the limited data from the later TOPEX / Poseidon mission was dominated by an El Nino event. Still, it’s what there was and I learned some valuable skills!
Twenty years later I found myself working with altimeter data again. The twist was that this time instead of preparing sea surface height data, I was going to use it!
Things change in two decades! The data which had taken me four years to prepare has now been surpassed with data not just from just two satellites with ground-track data every 7 km every 10 days, but from up to twelve satellites with data interpolated to daily resolution at 1/4-degree spatial resolution. And it only takes a few minutes to download! It’s a phenomenal improvement!
As well as the quality of the data, the global sea level has also increased dramatically in twenty years – by some 6 cm! That’s easily visible on the average shoreline because even disregarding increased coastal erosion this rise equates to the sea encroaching onto the beach by about an extra 70 cm.
Whilst the sea level has been busy rising, I’ve also been busy. Of note, working as a sediment transport scientist and presenting my results in Barcelona at a conference in 2005. This is noteworthy because my take home ‘message’ at “Coastal Dynamics 2005” ended up being my future wife!
She’s Dutch, and even though she speaks excellent English we ended up living in the Netherlands. As you can imagine, sea level – or “zeespiegel” – is pretty important here (hence my post-doc!)
I looked at the spatial variation of sea level change in the North Sea. Even along the relatively short Dutch coastline the rate of sea level rise varies with location by more than 1 mm/year. (By way of comparison, the global mean rate is about 3 mm/year). The spatial variation and understanding why it occurs is important because it means that regional coastal impacts can be better assessed. Ironically, it is the coastal areas which are the most difficult for satellite altimeters to monitor.
What does the future hold? Global sea level, the mean of all of its regional components, is set to continue its upward journey, as too the technology behind the satellite altimeters which will be monitoring it closely.
Here in the Netherlands the rate of my daughters’ upward growth will be faster than the current rate of sea level rise by approximately factor 20, and I’ll be watching them closely as well!
The picture of the bridge I’ve attached is across a local canal near our home. It’s a simple bridge and I’ve had simple pleasures on it with my daughters playing pooh sticks. Maybe in another 20 years they’ll be playing pooh sticks with their children. I wonder if by then this bridge will be over salt water?
Article originally published here (Page 39).
Paul
