Glacier Bay National Park & PreservePage 81 of 97
First Ocean and Wildlife Survey of Alaska's Outer-Coast Glacier Fjords, June 2022
Icy Bay currently hosts the largest seasonal gatherings of harbor seals in Alaska and in the world, and in June 2022 scientists made the first coordinated ocean surveys of its waters and those of three other glacier fjords. The Southeast Alaska Network of the National Park Service and the University of Alaska College of Fisheries and Ocean Sciences completed the first oceanographic, seabird and marine mammal monitoring mission along the outer coasts of Wrangell-St. Elias and Glacier Bay national parks and preserves. They worked from the R/V Wolstad from June 2 to 9, 2022.
A tidewater glacier. NPS/Jamie Womble.
The aim was to describe fjord and nearshore marine conditions in Disenchantment Bay, Yakutat Bay, Icy Bay and Lituya Bay. These were the first coordinated physical and biological oceanographic surveys of tidewater glacier fjords in this remote part of the eastern Gulf of Alaska. The team took physical, chemical and biological samples at about 70 stations and surveyed marine birds and mammals at the same time.
Sampling area and the kinds of data collected.
Preliminary results
| Subject | What the team found |
|---|---|
| Ocean temperature and salinity | Water temperatures ran from below 4 °C in Icy Bay near melting ice to above 11 °C near the surface on the shelf outside the fjords. Salinity was close to 32 near the bottom offshore, 31 to 31.5 below the surface in the fjords and 25 to 30.5 at the surface. Stratification near the surface generally held the mixed layer to the upper 33 feet (10 m) |
| Freshwater, fronts and turbidity | Density fronts, often tied to features such as sills, and freshwater plumes from melting glaciers and icebergs. Turbidity rose near melting ice, with chlorophyll blooms near the surface and in water colored by glacial till |
| Nutrients | Nitrate, phosphate and silicic acid were low in all four fjords, and generally higher on the shelf side than near glaciers and freshwater. Chlorophyll-a was low across the region, with phytoplankton found in the upper 65 feet (20 m) |
| Phytoplankton | Mostly small nano- and picoplankton (0.7 to 20 µm), with few of the larger diatoms (over 20 µm), though diatoms peaked at the head of Icy Bay in the freshwater lens from ice melt |
| Zooplankton | Mostly small to medium copepods, including Oithona similis, Calanus marshallae, Acartia longiremis and the Pseudocalanus species complex, plus juvenile krill and the pteropod (pelagic snail) Limacina helicina |
| Ocean acidification | All four bays were oversaturated with calcite (Ω above 1), a favorable condition for calcifying animals such as pteropods, crustaceans and echinoderms. Pockets nearing undersaturation (Ω below 1) turned up in Yakutat Bay and in shelf waters off and inside Lituya Bay. Aragonite saturation was low in all four bays, with undersaturated waters matching low calcite |
Temperature and salinity profiles for Icy Bay, Yakutat and Disenchantment Bays and Lituya Bay, 2022.
A CTD (conductivity, temperature and depth) rosette with Niskin water bottles being deployed near Lituya Bay. NPS/Jamie Womble.
Calcite (top) and aragonite (bottom) saturation states for the same bays.
Jellyfish and a mooring
A large bloom of the jellyfish Aequorea victoria turned up in Lituya Bay. The high densities probably come from warm sea surface temperatures and from the animals being trapped in the bay by its narrow entrance and the tides. In Disenchantment Bay the team deployed an overwintering oceanographic mooring that collects high-resolution physical and bio-optical data and underwater sound recordings. It is designed to be recovered and redeployed each year.
An oceanographic mooring being deployed in Disenchantment Bay. NPS/Jamie Womble.
Seabirds and marine mammals
Along the survey transects the team saw marbled and Kittlitz's murrelets, glaucous-winged gulls, black-legged kittiwakes, common murres, pelagic cormorants and Arctic terns. Cenotaph Island in Lituya Bay holds a large kittiwake colony and several pelagic cormorants. Harbor porpoises were seen in Lituya and Disenchantment Bays, and sea otters in all the fjords, mostly in nearshore areas and foraging over and near glacial sills.
Large groups of harbor seals, pups included, rested on icebergs in Disenchantment Bay and Icy Bay in Wrangell-St. Elias National Park and Preserve. Lituya Bay's tidewater glaciers gave seals iceberg habitat in the mid-1990s, but since those glaciers grounded, seals no longer use ice in that bay. About 270 Steller sea lions were hauled out on nearshore rocks near the entrance to Lituya Bay and south of it.
Black-legged kittiwakes on Cenotaph Island (left), a harbor seal and pup (middle) and Steller sea lions hauled out in Lituya Bay (right). NPS/Jamie Womble.
Sources
- National Park Service, "Where Ice Meets the Ocean: Outer Coast Field Update for 2022" (https://www.nps.gov/articles/000/outer-coast-2022.htm); rewritten in hubnx's own words. The page spells the jellyfish "Aequoria"; the spelling Aequorea is corrected here from the writer's knowledge.