USNA Polar Science Program ARCTIC SEA ICE: IN SITU MEASUREMENTS OF SEA ICE THICKNESS DURING NAVAL ACADEMY ICE EXERCISE 2013 IN BARROW, AK Midn 1/C Dagmara Broniatowska, United States Naval Academy LCDR John Woods, USN, United States Naval Academy Introduction The Arctic is the most influential environment on Earth in driving climate change. In the fall of 2012, the sea ice extent was the smallest ever recorded. The ice thickness, however, is what is becoming the most concerning feature of the sea ice. With the big melts that we have experienced in the past decade, the multiyear ice is disappearing and being replaced by thin one year ice that cannot survive the following year’s melt season. An ice diminished Arctic is an important consideration for the United States Navy. The purpose of the first Naval Academy Ice Experiment was to expose future naval officers to the harsh conditions of the Arctic, familiarize them with basic sea ice field work and, ultimately, to raise awareness of the Arctic’s importance. Procedure During NAICEX, the in situ measurements of sea ice thickness along the 1km straight line were collected every 25m. To measure ice thickness, the optimal number of personnel conducting research is two. The procedure starts with measuring the snow depth at the place of the drill hole. Then, with a shovel the snow is removed until the ice surface is exposed. One person drills the initial hole with the shortest auger. If the ice surface is flat, the procedure can begin with the 2m auger to save time. Augers are exchanged from the shortest one to the longest one until the water is reached. The hole should be cleaned as much as possible from the floating ice chips by rapidly moving the auger up and down. After all the ice is removed, a person measures the thickness of the ice with the measuring gauge. The measuring gauge consists of a meter tape and a brass tug, “T-anchor”, that, once dropped through the borehole, bridges across it. After reading the measurement, the person measuring pulls on the tape, the tug folds, and then can be retreated. Next, the freeboard is measured with a ordinary measuring tape. All the measurements and the time are logged. It is suggested to switch the person operating the augers after each meter to avoid exhaustion. Conclusions Data collected during NAICEX 2013 provides accurate measurements of the sea ice and snow thickness. The biggest challenge was to organize the field data in time to present this paper. In the future, this data can be compared with the LIDAR measurements from the CRYOSAT-2 and those collected by the Naval Research Laboratory. This will help validate the satellite instruments in order to ensure the accuracy of the measurements over a large area. Sea ice thickness is important in climate research and predictions as it determines the ice age and the potential for the ice to survive the melt season. This information will be more and more required as the traffic in the Arctic and the presence of the Navy increases. The Navy will need to be prepared to assist with rescue missions as well as environmental disasters and potential conflicts. NAICEX was organized by the USNA Polar Science Program. USNA PSP provides opportunities for future officers to work in the harsh conditions of the Arctic – an environment that they may be operating in in the near future. USNA PSP is an interdisciplinary program that combines both science and engineering majors. It is involved with the USNA STEM office and in raising awareness in young generations about the importance of the Arctic and science in general. S. Nghiem NASA/JPL The change in sea ice thickness between March 2012 and March March 2012 March 2013 NAICEX 2013 operating area 1/C Newnam drills boreholes with a 3m hand operated auger cutter to take sea ice thickness measurements C. Linder Chris Linder Photography Acknowledgments: University of Delaware - Prof. Cathleen Geiger; University of Washington - Dr. Ignatius Rigor; Naval Research Laboratory; Office of Naval Research; UMIAQ. Results During the experiment a total of 41 bore holes were made and measured along the 1km line. The results show the presence of two major ridges that developed mostly beneath the sea ice. None of these ridges were grounded, which MIND 1/C Broniatowska measures the sea ice thickness with the measuring gauge. MIDN 1/C Newnam records the thickness in the weatherproof notebook. Measuring gauge with a brass “T-anchor”. Different sea ice measurements that can be taken with a measuring tape and gauge. Conducted by in situ measurements or satellite to derive the ice thickness over a larger are. C. Linder Chris Linder Photography Source: Sample of the Excel Spread Sheet with the in situ data from NAICEX 2013 Sea ice thickness distribution obtained from the in situ measurements collected in Barrow, AK from 11 th to 14 th March during NAICEX 2013 NARL, Barrow Open Lead indicates that approximately 0.5 miles offshore the ocean depth is greater than 2.6m. The average ice thickness in the area is 153.6cm. The outlined box on the graph above indicates a small ridge that can be seen from the top view of the ice camp. This ridge formed a barrier between the rumpled ice, which we observe between -300 – 100m and further to the right of 200m mark. The main source of error in the in situ measurements obtained at NAICEX is human. With a thick cover of snow above the measured surface, it is hard to exactly read the boarder between wet snow and sea ice. The measurements were taken within an accuracy of 1cm. In the future, there needs to be more consideration of the time of the day that the measurements are taken, because the sea level differs due to tides. The top view of the NAICEX camp