Section K and Coronation Island

Coronation Island and clouds on the morning of 29 April 2017. Many of the wave-like clouds arise from leewaves, also known as mountain waves.

Section K measurements

Saturday, 29 April 2017 from the Scotia Sea, on the north side of the Orkney Passage. 

The air hovers around -10C with 10-20 knot winds. Sun sprinkles through overcast skies. Coronation Island shields us from open ocean swell.  Sei, minke, and gray whales poke around the ship, feeding, investigating, and cruising.

We have been near Coronation Island for the past three days. We completed a CTD section (Section K for “Kurt”) yesterday, then an overnight tow-yo completed this morning covering much of the same region. Today, we recovered Kurt’s mooring deployed on 22 March (see post then).

 

Kurt doing some good-luck yoga prior to recovering his mooring on 29 April 2017. Or, perhaps he is just trying to warm up in the cold air?

After recovering Kurt’s mooring, we started a deep (5400 metres) VMP/CTD station at the northern end of the section. We hope that this station will provide a bound to this very rich section, perhaps offering somewhat quiet data station as a benchmark to compare with the other more dynamically active stations. 

Grant, Andy, Paul, and Steve removing one of the mooring instruments.

After this station, we will move a bit west to tow-yo along two new sections, offered to us by the grace of fair weather and seas. These sections were chosen due to their rather steep bottom topography, thus favoring strong bottom currents and fluid instabilities of interest during this cruise.  We thus hope these tow-yos will continue to reveal elements of the rich dynamical features seen through much of our Orkney Passage cruise. The tow-yos are scheduled for completion Monday morning, 01May. That task will then conclude our roughly seven weeks of science measurements.

We are excited about the measurements.  Indeed, there are various ideas floated concerning how to dynamically interpret what we are seeing. Alas, a compelling science story will likely take months if not years. 

A bird's eye view of the mooring recovery on 29 April.

Atmospheric fluid dynamics around Coronation Island

The mountains, sea, and sky around Coronation Island express elements of fluid dynamics that would touch many a scientist’s heart and head. In one direction, cloud formations manifest leewaves emanating downstream (the ''lee'' side) from the mountains. These waves arise from atmospheric winds passing over the island’s mountains. Mountains lift stratified air through the earth’s gravity field. As the lifted air moves downstream from the mountains, gravity creates a rebound effect that sends waves down then up again.  The trail of waves is visualized by clouds that form when the rising air moves into colder air aloft, in which case water vapor condenses into ice crystals thus forming a cloud. Some clouds appear as dragons with razor sharp claws that scratch at the sky. Others form the wings of a planetary bird holding up the heavens.Still others appear as lens-like flying saucers emanating from the mountain.

On another horizon, overturning clouds break like water waves on the beach.  They reveal roiling Kelvin-Helmholtz billows that arise from stratified shear instability.  I can imagine the cat’s eye features that signal efficient stirring and mixing of air parcels in the fluid layers far above these distant mountains. 

Some other-worldly post-card images from Coronation Island. The top left shows some mountain waves reaching up from the island. The top right reveals more mountain waves reminiscent of flying saucers.  The lower panel shows signs of shear instability, with subsequent pictures (not shown) revealing the unstable waves in the dark clouds moving to the left. Each of these clouds have more technical names. These sorts of cloud views would make nearly anyone want to know more about cloud phenomenology and dynamics. 

Mountain waves (aka topographic leewaves) and Kelvin-Helmholtz billows are fluid dynamical features that also take place within the ocean.  Indeed, some of the measurements may be signals of these processes, or to other related fluid processes.  Whereas atmospheric scientists can readily view the objects of their study, deep sea oceanographers must rely in instruments sent thousands of metres into the abyss.  Interpreting these measurements requires a strong grounding in geophysical fluid mechanics. It also requires an internal visualization and imagination to nurture ideas and understanding. Some ideas are off the mark, but others hit the target, which in turn can lead to further insights and explorations.  

More images from Coronation Island.  The mountain view on the top left was our nearest neighbor, and it sits in the middle of the more panaramic view at the bottom.  The middle left shows Coronation Island as a backdrop to two or three whales cruising by the ship.  The top right is a far distant portion of the island.  I darkened the image by removing most of the light, thus revealing the white caps on a dark sea, the mountains, and the layered clouds.  This portion of the island was often shrouded in mist and fog.  Contemplating its far shores occupied a great deal of my dream time on top of Monkey Island.

Personal reflections on Coronation Island

During the past three days, the morning sun revealed distinct facets of this spectacular primordial place known as Coronation Island. Clouds shroud glacier covered mountains that spill into the sea. Light reveals for a moment the underlying geology, only to be covered minutes later by a thick cloud blown by winds swirling over rocky ridges and glacial crevasses.  Atmospheric molecules scatter short light waves, thus exposing the longer waves that offer stellar sunrises over the island and sea.

Coronation Island juts out of the sea without the hint of a shoreline. Views of the shoreline are hindered by a mirage. The mirage arises from the relatively warm 0C ocean that is cooled by the -10C windy air above.  The heat sucked out of the ocean sends radiant plumes into the atmosphere, just like hot air rising above the desert.  The mirage transforms a rocky shoreline into a vertical cliff.  It is as if this island does not wish to host any people. Instead, it prefers to be seen from afar.

The clouds and mountains seem as if from another planet.  Or perhaps this extra-terrestrial impression is just my mind unaccustomed to extreme juxtapositions of mountain, atmosphere, and ocean.  Indeed, this strangely beautiful and ancient place is foreign to my normal experience. It nonetheless has been deeply compelling and penetrating to my soul.  Sacred and mystical capture the sense that Coronation Island gives as I stare and wander and dream at its distance.

The island is just a few miles away, with a palpable presence as if I am standing on its shore. I float on a ship above its crustal roots living deep beneath the ocean where whales, penguins, and krill move through their flow field. Photos are taken, and more yet again.  Alas, to capture the presence of this place on a digital image is an elusive quest. Its deeper reality is best felt in the bones and heart.

During this cruise, I have stood for hours on the Monkey Island atop the ship’s navigation bridge. I have felt the incessant winds and been mesmerized by never-ending waves.  I have explored multitudes of skyscapes.  I have become tuned to water spouts exhaled from cruising whales and the fleeting glimpses of penguins flying through the waters. Yet perhaps more than any other vista on this trip, Coronation Island has me fixated and astonished. It has me magnetized as the sun rises over the island. Its dynamic vistas are stunning. They bring tears of amazement and gratitude.  Toes and fingers are near frost bite as I am blown open. I must return to the UIC as the next CTD is prepared.  Well, perhaps I will return to work after just a few more moments on Monkey Island. 

There were many colours to be seen. Yet for a number of photos, I found that black and white nicely focused my eye on the many shapes and textures revealed by the sea, land, and sky.