With sea ice in full retreat, a start to sampling

While it prevented LTER scientists from getting into the field until mid-December, the persistent sea ice was no obstacle for an elephant seal that climbed up onto the rocks surrounding the station on Dec. 12.

Charismatic megafauna: Indisputably charismatic. While the persistent sea ice prevented LTER scientists from getting on the water until mid-December, it was no obstacle for an elephant seal who climbed up onto the rocks surrounding the station on Dec. 12.

After a long and inexcusable absence from this space, greetings again from 64º south. Some milestones have passed since my last update on Nov. 18. We’ve celebrated Thanksgiving, Christmas, and Hanukkah, each with good cheer and sustenance worthy of the best holiday gatherings stateside. For those USAP veterans who call this remote place home, the celebrations were that much more meaningful.

Christmas Day saw the scheduled arrival in Arthur Harbor of at least two Minke whales. Station lore holds that the season’s first whales always show up on Christmas Day; after fulfilling their contractual obligation with a brief show of breaching and splashing, this year’s travelers quickly moved on in search of food.

Sunset from atop the glacier on Dec. 21. The solstice brought just 135 minutes of official nightfall to Palmer Station.

Sunset from atop the glacier on Dec. 21. The solstice brought just 135 minutes of official nightfall to Palmer Station.

On Dec. 21, the Summer Solstice brought Palmer its longest day of the year. Just 135 minutes of official nightfall separated sunset, which occurred shortly after midnight, from the sun’s appearance on the horizon again at 2:22 a.m. Something between dawn and twilight persisted in the intervening hours — more than enough light for skiing up on the glacier or for a midnight walk through the moraine and glacial outwash that litters the station’s backyard.

A Nov. 30 image from the RadarSat-2 satellite showed the extent of the sea ice that lingered for months to the south and west of Anvers Island. In this false-color image, sea ice is white, while land masses and terrestrial ice have a blueish tint.

A Nov. 30 image from the RadarSat-2 satellite showed the extent of the sea ice that lingered for months to the south and west of Anvers Island. In this false-color image, sea ice is white, while land masses and terrestrial ice have a blueish tint. Station scientists and ship personnel use these images for scientific planning and navigational awareness.

And, for the scientists of the Palmer LTER study, the holidays ushered in another highly-anticipated event: The retreat of an anomalously persistent cover of sea ice to the south and west of Anvers Island,  which had prevented us from sampling for nearly three months. After a few days of favorable winds (see my earlier post, here), the morning of Dec. 27 finally brought the open water that allows us to collect samples for the first time at both of the study’s offshore sampling stations.

The stations — “B” and “E” — are two of the roughly 20 predesignated scientific sampling locations that dot the waters adjacent to Palmer Station. The LTER study collects samples at these two particular stations because they are ecosystem endmembers; samples from the two locations capture the major elements that shape the unique marine ecosystem surrounding Anvers Island. (The term endmember was originally used in geology and geochemistry to describe a mineral or rock representing one end of a series having a range of composition; today, biogeochemists and other earth scientists use the term to describe the two or more extremes of any system that can be characterized by mixing of elements with distinct properties.)

Samples collected at Station E capture the direct influence on the ecosystem of the Southern Ocean and Amundsen Sea. Station E is roughly 3 miles from shore, seaward of the small rocky islands that surround Palmer Station. The water depth at Station E is somewhere around 120 meters, and the salinity of the water is nearly 35, that of average ocean water.

In comparison, Station B is less than a half-mile from the nearest point of land, and fresh glacial meltwater typically lowers the salinity there to around 32 or 33. In the spring, runoff from nearby penguin colonies can increase the concentration at Station B of certain dissolved nutrients. And, “B” is shallower, with a depth of about 60 meters.

Antarctic sea ice extent in 2013 (bottom) and in 2011 (top). Relative to the trend established in the past 30 years, the 2013 sea ice cover on the West Antarctic Peninsula was anomalously extensive. The orange line shows the median ice extent surrounding the continent over the past few decades. While the extent and duration of the sea ice cover on the Peninsula has decreased dramatically over the past few decades, ice surrounding the continent as a whole has increased slightly.

Antarctic sea ice extent in 2013 (bottom) and in 2011 (top). Relative to the past 30 years, 2013 sea ice cover on the West Antarctic Peninsula was anomalously extensive. The orange line shows the median ice extent surrounding the continent over the past few decades. While the extent and duration of sea ice cover on the Peninsula has decreased dramatically over the past few decades, ice surrounding the continent as a whole has increased slightly.

At each site, we apply the bread-and-butter techniques of modern oceanography, combining the collection water samples from several depths in the water column with profiles of temperature, salinity, and the water’s optical properties using electronic instruments. By measuring certain properties of the water collected at the different depths, we can compare the two distinct but often overlapping populations of microbes that make their living at the two stations.

We divide up the water we collect for dozens of different types of analysis. On a normal day, for example, we set aside some of the water to measure the different pigments produced by the various algae at the two sites, chlorophyll being just one of many pigments used in photosynthesis. Another subsample is used to determine  the concentration in the water of dissolved organic carbon, or DOC, the billions of dissolved organic compounds that are suspended in every milliliter of seawater.

I had hoped to begin writing about the LTER sampling effort in late October or early November, the time when LTER sampling crews have traditionally begun their work in years past. But as I’ve described in this space throughout the spring, the uncharacteristic lateness of this year’s sea ice retreat — and the anomalously broad extent of the ice pack along the Peninsula for much of the winter — prevented us from conducting any real sampling.

It turns out this anomalous year has been as frustrating for us in the field as it has been a source of keen scientific interest among the many scientists back in the U.S. who conduct field work at Palmer Station.

Climatically, this year is a certain anomaly: West Antarctica, and the Peninsula in particular, remain among the fastest winter-warming locations on earth. (See, for example, a plot in this earlier post showing the dramatic decline over the past few decades in annual sea ice cover.) For whatever reason — the cause will be a source of scientific inquiry and debate over the next few years — the 2013 sea ice retreat defied the trend.

Austin Melillo, a geology student at Rutgers University, helps deploy the LTER CTD (conductivity, temperature, and depth) package amid sea ice at Station B.

Science, finally underway. Austin Melillo, a geology student at Rutgers University, helps deploy the LTER CTD (conductivity, temperature, and depth) package amid sea ice at Station B.

From the dining room here at Palmer Station, taking in the frozen sea day after day for nearly three months, I found it difficult to remember this was still a region of intense climatic change. Trends and anomalies in climate do not lend themselves to the standards and measures of human lives. We think on the timescales of months and seasons, comparing this year to the last and the next year to this one. Our human memories are short, and changes in climate occur over time intervals that often defy our comprehension.

As a scientist, I try to remember this. And I remind myself that the data we collect over the next few months as part of the LTER study may help to elucidate the causes and effects of the massive changes here in West Antarctica. Rationally, I know this year was an exception to an alarming trend. And yet, like all scientists, I am certainly human: It was difficult to look out at all the ice — more than anyone had seen in twenty years, yet an amount that used to be normal here 50 years ago — and remember that I was staring at an anomaly.

More to come from Palmer Station and the Laurence M. Gould. In the meantime, a few more images from the past month on station:

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Exceptionally calm water and remnants of the sea ice pack greeted us on our first trip to Station E.

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A leopard seal hauled out on an ice floe.

A leopard seal hauled out on an ice floe.

An enormous iceberg lingered just a few hundred yards from Station E as we collected water samples on Dec. 27.

This enormous iceberg lingered just a few hundred yards from Station E as we collected water samples on Dec. 27.

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