When all the ice melts

Pan fydd yr holl iâ’n toddi, bydd y môr yn cyrraedd fan hyn
When all the ice melts, the sea will be up to here

when all the ice melts …

When all the ice on earth melts, the average level of the sea will be around 200 feet higher than it is now.

It will take thousands of years for the sea to deepen by 200 feet (which it will if the Earth’s temperature continues to increase). About five thousand years seems to be the timescale.

Five thousand years, you say? Way too big a stretch of time to think about. But there were people like you and me living five thousand years ago, with writing and money and organised religion and civil engineering and agriculture and  beautiful art.

Think of a 200-foot depth of water inching its way upwards, slowly, deepening relentlessly. I live beside the sea, and this is what I’ve been thinking about recently. Indeed, I live next to a large swathe of low-lying land that was sea 220 years ago, until the Cob was built across the Afon Glaslyn at Porthmadog.

cofiwch cantre’r gwaelod

In 2019 the Extinction Rebellion Cymru banner at the head of this post was positioned on the Cob. In the Welsh language ‘Cofiwch’ is the command ‘Remember’. Remember the  submerged land of Cantre’r Gwaelod, which, according to legend, is now under the waters of Cardigan Bay. The earliest version of this story is in the Medieval Black Book of Carmarthen – Cantre’r Gwaelod is a vivid and deep part of the Welsh psyche.

useful information

This is a useful interactive map to look at the result of different heights of sea level rise. For +200 feet, use a rise of 61 metres. And this article looks at ways of adapting to rising sea levels, with suggested further reading.

As at March 2022, both the Arctic and Antarctic are vastly warmer than they should be for the time of year, and in the Antarctic the 1,200 square kilometre Conger ice shelf has collapsed.

This  series of short BBC programmes/podcasts explores different tipping points in climate change, including in relation to the Arctic, the Antarctic, and ocean circulation.

my project

In autumn 2021, I started cycling and walking (and occasionally bussing it) to points near me where roads and public rights of way cross the 200-foot contour, and pinning up a Post-it note saying:

Pan fydd yr holl iâ’n toddi, bydd y môr yn cyrraedd fan hyn.
When all the ice melts, the sea will be up to here.

It is the thing I have been mostly writing lately. Over and over.

other art prompted by rising sea level

It turns out the same impetus that sends me out with Post-it notes and drawing pins has stimulated other pieces of art – on much grander scales. There is this one, in Còmhghall in Scotland, so I guess I should also say:

Nuair a leagh an deigh uile, bidh uisge na mara suas chun na h-àirde seo.

And there is also this one, The (Future) Wales Coast Path, which is taking place in Newport and Magor in South Wales throughout 2022.

the photos

All the photos below were taken in North Wales, grouped by the watercourse that will grow deeper with rising sea level. They are arranged east to west, with the 200′ point nearest the coast being the first photo in each group. The longer rivers are divided into sections.

The longest river is Afon Glaslyn, which rises on Yr Wyddfa (Snowdon). The 200′ contour of its catchment intersects with the highway/public footpath network in Nantgwynant,  near the start of the Watkin Path up Yr Wyddfa.

Tributaries to the main rivers are shown in the order that they join the main body of water. These are:

  • Nant yr Afon-oer and Afon Rhyd/Afon Caseg join Afon Glaslyn where it is currently tidal
  • Nanmor joins Afon Glaslyn in the stretch between Pont Croesor and Pont Aberglaslyn
  • Afon Colwyn joints Afon Glaslyn between Pont Aberglaslyn and Pont Bethania
  • Afon Prysor joins Afon Dwyryd where it is currently tidal
  • Afon Teigl joins Afon Dwyryd inland from Pont Maentwrog
Afon Dwyfor

Field drains, un-named on OS maps

Nant y Wyddan and Ffrwd y Brain


Afon Glaslyn – where currently tidal, up to Pont Croesor

Nant yr Afon-oer

Afon Rhyd or Afon Caseg

Afon Glaslyn – from Pont Croesor to Pont Aberglaslyn


Afon Glaslyn– Pont Aberglaslyn to Pont Bethania

Afon Colwyn

Afon Glaslyn – Nantgwynant inland from Pont Bethania

Afon Dwyryd – where currently tidal, up to Pont Maentwrog

Afon Prysor

Afon Dwyryd – inland from Pont Maentwrog

Afon Teigl

In each of these photos there’s a Post-it note pinned to something, saying the same thing:

Pan fydd yr holl iâ’n toddi, bydd y môr yn cyrraedd fan hyn.

When all the ice melts, the sea will be up to here.

All words and all images ©Susan Walton 2021 and 2022.