Basic hydrology, limnology, and climatology

1
Basic hydrology, limnology, and climatology of
the Elgygytgyn Crater region Matt Nolan
University of Alaska Fairbanks Julie
Brigham-Grette UMass Amherst With
support from the U.S. National Science
Foundation, Kristin Scott Nolan, and the Lake
Elgytygyn international science team
2
Physical Overview of Lake Elgygytgyn
AreaDigital Elevation Model
N
The Bears Back
1998 Core
Walrus Snout Point
Snout Bay
Buckle Point
Outlet
We created a digital elevation model of the
region which can be used in a variety of
terrestrial studies. The crater is roughly 18 km
in diameter with a watershed area of 293 km2 and
lake area of 110 km2.
3
Physical Overview of Lake Elgygytgyn
AreaDigital Elevation Model
Roughly 50 streams enter the lake and basic
physical statistics were compiled on them using
this DEM. This local stream numbering system
should be adopted by researchers here to
facilitate collaborations and minimize confusion.
Coordinates exist for all outlets.
4
Physical Overview of Lake Elgygytgyn AreaImagery
Water tracks
Submarine delta formation
We purchased Ikonos imagery of the crater region
in 2001. This imagery was used to make a variety
of 3D visualizations and is useful for a variety
of terrestrial studies.
5
Physical Overview of Lake Elgygytgyn
AreaBathymetry
Using bathymetry from Russian sources (which
seems quite accurate), we calculated lake volume
and hypsometries. The lake contains roughly 14
km3 of water. Though 175 meters seems deep, it
is actually shallow compared to its 12 km width.
6
Physical Overview of Lake Elgygytgyn AreaWeather
A weather station was established in July 2000,
and is presumably still running (if it hasnt
been shot again). This station records air
temperature, relative humidity, barometric
pressure, wind speed and direction, rainfall,
snow pack, solar radiation balance, and soil
moisture.
7
Physical Overview of Lake Elgygytgyn AreaWeather
August 31
September 1
Enough said about how quickly the weather can
change?
8
Physical Overview of Lake Elgygytgyn AreaWeather
Bedrock
Prograding stream sediments
Locally measured wind directions indicate a
dominant trend. We hypothesize that this trend
leads to water currents which work in concert
with the stream delta formation on the western
shore to create the unique shape of the lake.
9
Physical Overview of Lake Elgygytgyn AreaWeather
Crater rim and center
Bedrock
Prograding stream sediments
Locally measured wind directions indicate a
dominant trend. We hypothesize that this trend
leads to water currents which work in concert
with the stream delta formation on the western
shore to create the unique shape of the lake.
That is, the center of the crater is not
directly beneath the center of the lake.
10
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
Thermistor strings located in the deepest part of
the lake indicate a textbook pattern of
temperature stratification in winter and complete
mixing in summer. We did not detect any
thermocline in summer, likely due to constant
winds stirring up the water in this wide, thin
lake.
11
Physical Overview of Lake Elgygytgyn AreaWeather
Locally measured air temperature compares quite
well with the NCEP global reanalysis model output
for this area, indicating that the NCEP model
(running from 1948 to present) can be used as a
reliable proxy for real measurements when needed.

12
Physical Overview of Lake Elgygytgyn AreaWeather
Given this good correlation, the NCEP data can
also be used to help understand the dominant
storm tracks and climate trends here, which is
something I plan to do in the near future, using
tools like Hysplit and self-organized SLP maps as
seen here.
13
Physical Overview of Lake Elgygytgyn AreaWeather
The NCEP reanalysis (1948-2002) is used to create
give a sense of typical air temperature
conditions throughout the year. March and April
will no doubt be the most comfortable and
productive times for winter drilling.
14
Physical Overview of Lake Elgygytgyn AreaWeather
The NCEP reanalysis indicates that the region is
currently undergoing a warming trend. This
warming trend is being driven by winters with
fewer extreme low temperatures, which is good for
winter drilling. Its still plenty cold enough
to make thick ice though.
15
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
We used space-borne SAR to track lake ice
dynamics, including freeze-up, snowmelt, and
breakup. Here, an interesting pattern of lake
ice bubbles is seen developing.
16
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
These bubbles (the bright areas) are likely
caused by the respiration and decomposition of
living things. Given that the water is less than
3C, it is likely that warm dense water from the
shallow shelves sinks to the deepest part of the
lake, even in winter, suggesting the deepest area
may be biogeochemically different than its
surroundings.
17
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
We can determine the onset of snowmelt by the
disappearance of the bullseye pattern, because
SAR cannot penetrate wet snow.
18
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
The northern edge of the lake is usually blown
free of snow, piling it up deeper to the south
(as much as 1.5 meters). Ice melt begins at the
edges of the lake, where the shelves are present
and surface streams pile up warm water.
19
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
Lake ice breakup begins with moat formation along
the margins. This frees the ice to move with the
wind, where it begins getting hung up with the
deltas at streams 12-14 (Snout Point and Buckle
Point). Once these leads form, large pans are
free to rotate and crush, leading to rapid
distintigration of the candle ice.
20
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
I plan to update this chart and combine it with
further modeling as part of new work.
21
Physical Overview of Lake Elgygytgyn AreaLake
Ice Dynamics and Water Mixing
We can model lake ice breakup pretty well. As
part of new work, I hope to determine the range
of condition necessary to maintain a permanent
ice cover, as well as model ice sublimation, to
determine the conditions necessary for lake
levels to drop substantially.
22
Physical Overview of Lake Elgygytgyn
AreaOutreach
We have a number of 3D visualizations of the lake
online. These give a good sense of the what the
crater region is like. You can also find some
360 panoramas there.
23
Physical Overview of Lake Elgygytgyn
AreaOutreach
As part of future work, I plan to create several
hundred high resolution spherical panoramas of
the crater, in different seasons. Im happy to
train others to do this too. Here is a demo of
a similar project I am doing in north-eastern
Alaska.