When sun, moon and earth are in alignment and in closest proximity to each other, the sea responds by producing the highest tides of the year, known as king tides. These tides can be 30 or 40 centimetres higher than a normal spring tide, and since that is the expected increase in global sea level by mid-century, today’s king tides show us what ordinary spring tides will be like in 2050.
For low-lying atolls like Tarawa, capital of Kiribati, that new baseline will be a problem. When I visited Tarawa in April 2015 to research a story on sea-level rise the islands were still repairing seawalls and re-armouring vulnerable areas of coastline after damage inflicted by a king tide in February. That event closed the maternity ward in one of Tarawa’s hospitals, not far from where a shipwreck was pushed ashore, piercing a seawall.
Photographs I took of the damage and repair work have just been published on National Geographic’s website, here.
The challenge for all low-lying atolls—indeed, for all coastlines—is that as the sea creeps higher, coastal defences such as seawalls and rock barricades will be more frequently and more severely tested, and in some cases the cost of protection will rise to untenable levels.