Imagine a place where your vision is filled by all the shades of blue at once. A place where bright white foam rolls on the distant horizon, cumulus clouds tinged in gray roll beneath the cirrus that streak across a royal blue sky, above an ocean that shimmers in shades of turquoise as you trace a line from the far horizon to your feet. If you soften your eyes just a bit, you can almost see the curvature of the Earth. This is how I will remember the South Pacific Ocean.

The colors seemed to layer up on each other from beneath the sea to the sky. In the morning and evenings, the they transitioned from shades of blue to lavender, then clouds turned the color of ripe peaches, while the ocean was the color of melted orange sorbet. I didn’t come up with that – I heard someone describe that orange, and I thought it was perfect.

As an Earth scientist, I’m accustomed to thinking of how things work in layers. There are layers in the atmosphere, layers in the ocean, layers within the Earth. When we create computer simulations of the earth system, our simulations are coded in layers. Sometimes these layers are artificially imposed. We know there aren’t always real layers, but they help us simplify the complexity inherent in the real world. They allow us to see the big patterns, the wide vistas, the first-order effects.

Whenever I think back to my first trip to Tahiti, I will think of the layers. There, it was easy to see myself as a small smudge moving within that layer between ocean and atmosphere.

French Polynesia was not a place I had on my immediate travel horizon, but it held a prominent place in my mind. My mom rewarded herself after surviving her first bout of cancer with two trips to Tahiti (the second happened only a year after the first because I think she realized she was on a short timeline). And then Dad called late this spring and asked if I would join him and his friend Linda on a trip to Tahiti this summer. How can you say no to Tahiti?

So that’s how I found myself, on the shore of a South Pacific reef island (or motu) at sunset, contemplating layers.

August is the Tahitian winter. The sky is mostly clear, and the water is cool – cooler than you’d expect in the tropics, anyway. Daytime high temperatures stay in the mid-70’s, and the trade winds are strong enough to steal the hat from your head if you’re not careful. The clear air and ever-changing gallery of clouds in the sky mean that there are unimpeded views of sunrises and sunsets, and each one has a pallet of colors that shout SUMMER. That doesn’t mean you can tell which are the sunrises and which are the sunsets when you arrive home and look at your photos. But each one shows me a new layer of clouds, born from tropical humidity and driven by the Tradewinds.

The Tahitian islands are sinking volcanoes. Over thousands of years, the reef encircling each island builds on itself, layer upon layer, to create a barrier from the fury of the open ocean. In the lagoons and shallow spots that sometimes sit a mile or more from the shore of the island, there is an ecosystem as diverse and as colorful as any tropical rainforest. At least, that’s how it used to be.

I had hoped I would find in Tahiti a glimpse of the coral reefs as I remembered them in Hawaii, 30 or 40 years ago. I know that all reefs are struggling, and we have lost so many in the past two decades. But I hoped I would come upon a thriving reef – in this place shaped by reefs. I should have known better. Most shallow reefs – the ones that are easy to get to and frequented by tourists – were damaged long ago and baked in warming ocean waters. They lie lifeless in an algae-cloaked graveyard.

But wait! Aren’t the corals in the Great Barrier Reef making a comeback? After all, this is the word on the street. The answer to that is: yes and no. There has been a recovery of coral in the past couple of years – but it is mostly one species, the Acropora coral. This is a species that specializes in rapid recovery and grows very fast, but it is also susceptible to the same pressures that have damaged the rest of the reef. With ongoing marine heatwaves of the magnitude that have impacted the reefs everywhere in the past 20 years, they will likely also die in the near future.

In the next 30 years (by 2050), sea level is expected to rise nearly a foot. I think of this as a thickening of that upper ocean layer. Even in apathetic circles of U.S. policy discussion, this is alarming, and clearly spells out doom for many U.S. coastal cities. In French Polynesia, this would mean the end of many low lying barrier reef islands (the motus) and near-certain inundation in populated low-lying areas of every major island. Additionally, with a reefs weakened or killed by warm waters, islands will be more vulnerable to heavy storms. French Polynesia is actually contemplating constructing floating islands, as a way to adapt to rising seas, but it remains to be seen how practical that is.

I know that some of you reading this are thinking: Geez, Cindy! Can’t you just enjoy something without pulling us all down into climate grief?!?

I really wish I could. But understanding what is happening allows me to appreciate this fleeting glimpse of an old world before it’s gone completely. I feel such gratitude for being privileged enough to see this South Pacific paradise before it’s underwater. I want to savor it. And also feel that grief. Letting myself feel that moves me toward action.

Maybe I’m also prompted to think this way because there are so many places that have already been lost before I fully appreciated them. In 1995 I visited the Great Barrier Reef. Every time I visit the ocean, I feel a bit of sadness that the vibrant place I saw, teeming with life, no longer exists in the way I remember it. I wish I had understood at the time I was there that I would never see it like that again. I would have savored the experience more. Maybe I would have done more than skim the surface, just to say I’d seen the pretty colors of the Great Barrier Reef before hopping back on the backpacker bus to the next hostel.

There is some hopeful news coming from a place below the ocean’s surface. A large, deep reef was recently discovered near Tahiti that may be one of the healthiest reefs remaining in the world. It’s located at a depth of 30 meters below the surface, in what’s known as the ocean’s twilight zone. This is the lower limit of the sun’s ability to penetrate deep into the ocean. So this reef might also be somewhat less affected by the heat waves that happen near the interface between ocean and atmosphere. Maybe this reef can hold some clues for us about how to help reefs closer to the ocean surface.

I only spent a week in French Polynesia. It was a week spent skimming the surface – the surface of the ocean and the surface of this country. Beyond the natural beauty, this is a place steeped in a rich culture and history, and I didn’t really have a chance to dip much more than my toes in that richness. Polynesian culture has been shaped over a thousand years, and the people who lived here had such a strong connection with the ocean and with these islands. Maybe I will be lucky enough to go back and take a deeper dive someday. Hopefully before it’s transformed into something else completely.